Toxicology Glossary of Terms

A-J - #K - #L - #M - #N - #O - #P - #Q - #R
#S - #T - #U - #V - #W - #X - #Y - #Z




lachrymator: See lacrimator (#IUPAC)

lacrimator: Substance that irritates the eyes and causes the production of tears or increases the flow of tears (#IUPAC)

larvicide: Substance intended to kill larvae (#IUPAC)

laryngospasm: Reflex spasmodic closure of the sphincter of the larynx, particularly the glottic sphincter (#IUPAC)

larynx: Main organ of voice production, the part of the respiratory tract between the pharynx and the trachea (#IUPAC)

lassitude: Weakness; exhaustion (#IUPAC)

latent effect: See SN delayed effect (#IUPAC)

latent period: Delay between exposure to a disease-causing agent and the appearance of manifestations of the disease: also defined as the period from disease initiation to disease detection.
SN latency.
Last, 1988 (#IUPAC)

lavage: Irrigation or washing out of a hollow organ or cavity such as the stomach, intestine or the lungs.

laxative: Substance that causes evacuation of the intestinal contents.
SN cathartic, purgative (#IUPAC)

leaching: As water moves through soils or landfills, chemicals in the soil may dissolve in the water thereby contaminating the groundwater. This is called leaching (#Glossary)

1. Area of pathologically altered tissue.
2. Injury or wound.
3. Infected patch of skin.
lethal: Deadly; fatal; causing death.

lethal concentration: Concentration of a potentially toxic substance in an environmental medium that causes death following a certain period of exposure (denoted by LC).
WHO, 1979
RT effective concentration, lethal dose (#IUPAC)

LC50: LC stands for "Lethal Concentration". LC values usually refer to the concentration of a chemical in air but in environmental studies it can also mean the concentration of a chemical in water. For inhalation experiments, the concentration of the chemical in air that kills 50% of the test animals in a given time (usually four hours) is the LC50 value. (Canadian Center for Occupational Health and Safety)

lethal dose: Amount of a substance or physical agent (radiation) that causes death when taken into the body by a single absorption (denoted by LD).
RT effective dose, lethal concentration (#IUPAC)

LD50: LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. (Canadian Center for Occupational Health and Safety)

lethal synthesis: Metabolic formation of a highly toxic compound from one that is relatively non-toxic (bioactivation), often leading to death of affected cells.
SN suicide metabolism (#IUPAC)

leukaemia: Progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leucocytes and their precursors in the bone marrow and blood (#IUPAC)

leucopenia: Reduced concentration of leukocytes in the blood (#IUPAC)

lgKOW: See SN lgPow (#IUPAC)

lgPow: Logarithm of base 10 of the partition coefficient of a substance between octan-1-ol and water: as an empirical measure for lipophilicity used for calculating bioaccumulation, fish toxicity, membrane adsorption and penetration etc.
RT lipophilicity, octanol-water partition coefficient, partition coefficient.

life-long exposure: Subjection to a potentially toxic substance during the whole lifetime (#IUPAC)

lifetime exposure: Total amount of exposure to a substance that a human would receive in a lifetime (usually assumed to be 70 years).(1) (#CEHN)

limacide: Substance intended to kill mollusca including the gastropod mollusc, Limax (#IUPAC)

limit recommended: See recommended limit (#IUPAC)

limit test: Acute toxicity test in which, if no ill-effects occur at a pre-selected maximum dose, no further testing at greater exposure levels is required
Brown, 1988
RT fixed dose test (#IUPAC)

limit value (LV): Limit concentration at or below which Member States of the European Community must set their environmental quality standard and emission standard for a particular substance according to Community Directives
NT threshold limit value (#IUPAC)

limited evidence: According to the US EPA's guidelines for Carcinogen Risk Assessment, "limited evidence" is a collection of facts and accepted scientific inferences that suggests that an agent may be causing an effect, but this suggestion is not strong enough to be considered established fact.
IRIS, 1986
RT carcinogenicityclassificationaccordingtoIARC (#IUPAC)

linearized multistage model: Sequence of steps in which (a) a multistage model is fitted to tumour incidence data; (b) the maximum linear term consistent with the data is calculated; (c) the low-dose slope of the dose-response function is equated to the coefficient of the maximum linear term; and (d) the resulting slope is then equated to the upper bound of potency.
BT multistage model (#IUPAC)

lipophilic: Having an affinity for fat and high lipid solubility: a physicochemical property which describes a partitioning equilibrium of solute molecules between water and an immiscible organic solvent, favouring the latter, and which correlates with bioaccumulation.
RT bioaccumulation, bioaccumulation factor, bioconcentration, octanol-water partition coefficient.
SN hydrophobicity.
AN hydrophilicity, lipophobicity (#IUPAC)

lipophobic: Having a low affinity for fat and a high affinity for water.
RT bioaccumulation, bioaccumulation factor, bioconcentration, octanol-water partition coefficient.
SN hydrophilicity.
AN hydrophobicity, lipophilicity (#IUPAC)

liposome: Originally a lipid droplet in the endoplasmic reticulum of a fatty liver. Now applied to an artificially formed lipid droplet, small enough to form a relatively stable suspension in aqueous media and with potential use in drug delivery (#IUPAC)

local effect: Circumscribed change occurring at the site of contact between an organism and a toxicant.
RT systemic effect (#IUPAC)

logit transformation: Mathematical transformation that relates response to a stated dose or concentration of a toxicant to the response in the absence of the toxicant by the formula:
Logit = lg B/(B0-B)
where B is the response to the stated dose or concentration and B0 is the response in the absence of the toxicant. Plotting the logit function against the logarithm of base 10 of the dose or concentration usually gives a linear relationship (#IUPAC)

long-term effect: See SN chronic effect (#IUPAC)

long-term exposure: Continuous or repeated exposure to a substance over a long period of time, usually of several years in man, and of the greater part of the total life-span in animals or plants.
IRPTC, 1982
SN chronic exposure (#IUPAC)

lowest lethal concentration found: See SN minimum lethal concentration (#IUPAC)

lowest-observed-adverse-effect-level (LOAEL): Lowest concentration or amount of a substance, found by experiment or observation, which causes an adverse alteration of morphology, functional capacity, growth, development, or life span of a target organism distinguishable from normal (control) organisms of the same species and strain under defined conditions of exposure.
RT adverse effect, lowest-observed-effect-level, no-observed-adverse-effect-level, no-observed-effect-level (#IUPAC)

lowest-observed-effect-level (LOEL): Lowest concentration or amount of a substance, found by experiment or observation, that causes any alteration in morphology, functional capacity, growth, development, or life span of target organisms distinguishable from normal (control) organisms of the same species and strain under the same defined conditions of exposure
RT[ adverse effect|http://sis.nlm.nih.gov/enviro/glossarya.html#adverseeffect], lowest-observed-adverse-effect-level, no-observed-adverse-effect-level, no-observed-effect-level (#IUPAC)

lymphocyte: Animal cell that interacts with a foreign substance or organism, or one which it identifies as foreign, and initiates an immune response against the substance or organism. There are two groups of lymphocytes, B lymphocytes and T lymphocytes
NT B lymphocyte,[ immune response|http://sis.nlm.nih.gov/enviro/glossaryi.html#immuneresponse], T lymphocyte (#IUPAC)

lymphoma: General term comprising tumours and conditions allied to tumours arising from some or all of the cells of lymphoid tissue (#IUPAC)

lysimeter: Laboratory column of selected representative soil or a protected monolith of undisturbed field soil with which it is possible to sample and monitor the movement of water and substances (#IUPAC)

lysosome: Membrane-bound cytoplasmic organelle containing hydrolytic enzymes (#IUPAC)


macrophage: Large (10-20 mm diameter) amoeboid and phagocytic cell found in many tissues, especially in areas of inflammation; macrophages are derived from blood monocytes and play an important role in host defence mechanisms (#IUPAC)

macroscopic (gross) pathology: Study of changes associated with disease that are visible to the naked eye without the need for a microscope (#IUPAC)

Mad Hatter syndrome: See SN mercurialism (#IUPAC)

Magnusson and Kligman test: See SN guinea-pig maximisation test (#IUPAC)

mainstream smoke (tobacco smoking): Smoke that is inhaled
WHO, 1989a
RT sidestream smoke (#IUPAC)

malaise: Vague feeling of bodily discomfort (#IUPAC)

malignancy: Population of cells showing both uncontrolled growth and a tendency to invade and destroy other tissues; a malignancy is life-threatening
RT cancer, metastasis, tumour (#IUPAC)

1. Tending to become progressively worse and to result in death if not treated
2. In cancer, cells showing both uncontrolled growth and a tendency to invade and destroy other tissues
AN benign

mania: Emotional disorder (mental illness) characterized by an expansive and elated state (euphoria), rapid speech, flight of ideas, decreased need for sleep, distractability, grandiosity, poor judgement and increased motor activity (#IUPAC)

margin of exposure (MOE), margin of safety (MOS): Ratio of the no-observed-adverse-effect level (NOAEL) to the theoretical or estimated exposure dose (EED) or concentration (EEC)
RT therapeutic index (#IUPAC)

mass mean diameter: Diameter of a particle with a mass equal to the mean mass of all the particles in a population (#IUPAC)

mass median diameter: Diameter of a particle with the median mass of all the particles in a population
IAEA, 1978 (#IUPAC)

material safety data sheet (MSDS): Compilation of information required under the US OSHA Hazard Communication Standard on the identity of hazardous substances, health and physical hazards, exposure limits, and precautions
PS hazard communication standard, safety data sheet (#IUPAC)

maximum allowable (admissible, acceptable) concentration (MAC): Regulatory value defining the concentration that if inhaled daily (in the case of work people for 8 hours with a working week of 40 hours, in the case of the general population 24 hours) does not, in the present state of knowledge, appear capable of causing appreciable harm, however long delayed during the working life or during subsequent life or in subsequent generations
RT permissible exposure limit, threshold limit value (#IUPAC)

maximum average daily concentration of an atmospheric pollutant: Highest of the average daily concentrations recorded at a definite point of measurement during a certain period of observation
SN peak daily average concentration of an air pollutant
IRPTC, 1982 (#IUPAC)

maximum contaminant level (MCL): Under the Safe Drinking Water Act (USA), primary MCL is a regulatory concentration for drinking water which takes into account both adverse effects (including sensitive populations) and technological feasibility (including natural background levels): secondary MCL is a regulatory concentration based on "welfare", such as taste and staining, rather than health, but also takes into account technical feasibility. MCL Goals (MCLG) under the Safe Drinking Water Act do not consider feasibility and are zero for all human and animal carcinogens (#IUPAC)

maximum exposure limit (MEL): Occupational exposure limit legally defined in GB under COSHH as the maximum concentration of an airborne substance, averaged over a reference period, to which employees may be exposed by inhalation under any circumstances, and set on the advice of the HSC Advisory Committee on Toxic Substances
RT ceiling value (#IUPAC)

maximum permissible concentration (MPC): See SN maximum allowable concentration (#IUPAC)

maximum permissible daily dose: Maximum daily dose of substance whose penetration into a human body during a lifetime will not cause diseases or health hazards that can be detected by current investigation methods and will not adversely affect future generations (#IUPAC)

maximum permissible level (MPL): Level, usually a combination of time and concentration, beyond which any exposure of humans to a chemical or physical agent in their immediate environment is unsafe
RT maximum allowable concentration (#IUPAC)

maximum residue limit (MRL) for pesticide residues: Maximum contents of a pesticide residue (expressed as mg/kg fresh weight) recommended by the Codex Alimentarius Commission to be legally permitted in or on food commodities and animal feeds. MRL's are based on data obtained following good agricultural practice and foods derived from commodities that comply with the respective MRL's are intended to be toxicologically acceptable
Codex Alimentarius Commission, 1989 (#IUPAC)

maximum residue limit (MRL) for veterinary drugs: Maximum contents of a drug residue (expressed as mg/kg or g/kg fresh weight) recommended by the Codex Alimentarius Commission to be legally permitted or recognized as acceptable in or on food commodities and animal feeds. The MRL is based on the type and amount of residue considered to be without any toxicological hazard for human health as expressed by the acceptable daily intake (ADI) or on the basis of a temporary ADI that uses an additional uncertainty factor. It also takes into account other relevant public health risks as well as food technological aspects
Codex Alimentarius Commission, 1989 (#IUPAC)

maximum tolerable concentration (MTC): Highest concentration of a substance in an environmental medium that does not cause death of test organisms or species (denoted by LCo)
WHO, 1979 (#IUPAC)

maximum tolerable dose (MTD): Highest amount of a substance that, when introduced into the body, does not kill test animals (denoted by LDo) (#IUPAC)

maximum tolerable exposure level (MTEL): Maximum amount or concentration of a substance to which an organism can be exposed without leading to an adverse effect after prolonged exposure time (#IUPAC)

maximum tolerated dose (MTD): High dose used in chronic toxicity testing that is expected on the basis of an adequate subchronic study to produce limited toxicity when administered for the duration of the test period. It should not induce (a) overt toxicity, for example appreciable death of cells or organ dysfunction, or (b) toxic manifestations that are predicted materially to reduce the life span of the animals except as the result of neoplastic development or (c) 10% or greater retardation of body weight gain as compared with control animals. In some studies, toxicity that could interfere with a carcinogenic effect is specifically excluded from consideration (#IUPAC)

mean life: Average lifetime of a molecular, atomic, or nuclear system in a specified state. For an exponentially decaying system, it is the average time for the number of molecules, atoms or nuclei in a specified state to decrease by a factor of e, the base of natural logarithms
SN mean time
RT turnover time
ISO, 1972 (#IUPAC)

mean time: See SN mean life (#IUPAC)

media: Elements of a surrounding environment that can be sampled for contamination; usually soil, water, or air. Plants, as well as humans (when sampling blood, urine, etc) and animals (such as sampling fish to update fish consumption advisories) can also be considered media. The singular of "media" is "medium". (#Glossary)

median effective concentration (EC50): Statistically derived concentration of a substance in an environmental medium expected to produce a certain effect in 50% of test organisms in a given population under a defined set of conditions (#IUPAC)

median effective dose (ED50): Statistically derived dose of a chemical or physical agent (radiation) expected to produce a certain effect in 50% of test organisms in a given population or to produce a half-maximal effect in a biological system under a defined set of conditions (#IUPAC)

median lethal concentration (LC50): Statistically derived concentration of a substance in an environmental medium expected to kill 50% of organisms in a given population under a defined set of conditions (#IUPAC)

median lethal dose (LD50): Statistically derived dose of a chemical or physical agent (radiation) expected to kill 50% of organisms in a given population under a defined set of conditions. (#IUPAC)

median lethal time (TL50): Statistically derived average time interval during which 50% of a given population may be expected to die following acute administration of a chemical or physical agent (radiation) at a given concentration under a defined set of conditions (#IUPAC)

median narcotic concentration (NC50): Statistically derived concentration of a substance in an environmental medium expected to cause narcotic conditions in 50% of a given population under a defined set of conditions (#IUPAC)

median narcotic dose (ND50): Statistically derived dose of a substance expected to cause narcosis in 50% of test animals under a defined set of conditions (International)
medical monitoring
A set of medical tests and physical exams specifically designed to evaluate whether an individual's exposure could negatively affect that person's health (#ATSDR)

1. Process of "reductive" cell division, occurring in the production of gametes, by means of which each daughter nucleus receives half the number of chromosomes characteristic of the somatic cells of the species
RT chromosome,diploid, gamete, haploid
2. See miosis
mercurialism: Chronic poisoning caused by the excessive use of mercury, by breathing its vapour, or by exposure in mining or smelting processes.
SN Mad Hatter syndrome (#IUPAC)

mesocosm: See RT microcosm (International)

mesothelioma: Malignant tumour of the mesothelium of the pleura, pericardium or peritoneum, that may be caused by exposure to asbestos fibres and some other fibres
BT tumour
RT malignant (#IUPAC)

metabolic activation: Biotransformation of a substance of relatively low toxicity to a more toxic derivative
BT activation, biotransformation
NT lethal synthesis
SN bioactivation (#IUPAC)

metabolic half-life (half-time): Time required for one half of the quantity of a substance in the body to be metabolically transformed into a derivative or to be eliminated
SN metabolic half-time
RT clearance, elimination (#IUPAC)

metabolic model: Analysis and theoretical reconstruction of the way in which the body deals with a specific substance, showing the proportion of the intake that is absorbed, the proportion that is stored and in what tissues, the rate of breakdown in the body and the subsequent fate of the metabolic products, and the rate at which it is eliminated by different organs as unchanged substance or metabolites
WHO, 1989a (#IUPAC)

metabolic transformation: Biochemical transformation of a substance that takes place within an organism
SN biotransformation (#IUPAC)

metabolism: Sum total of all physical and chemical processes that take place within an organism; in a narrower sense, the physical and chemical changes that take place in a given substance within an organism. It includes the uptake and distribution within the body of chemical compounds, the changes (biotransformation) undergone by such substances, and the elimination of the compounds and of their metabolites
RT biotransformation (International)
metabolite: Any intermediate or product resulting from metabolism
After Nagel et al. (eds), 1991
RT biotransformation (#IUPAC)

metaplasia: Abnormal transformation of an adult, fully differentiated tissue of one kind into a differentiated tissue of another kind
RT hyperplasia, neoplasia (#IUPAC)

1. Movement of bacteria or body cells, especially cancer cells, from one part of the body to another, resulting in change in location of a diseaseisorders or of its symptoms from one part of the body to another
2. Growth of pathogenic micro-organismsor of abnormal cells distant from the site of their origin in the body
methaemoglobinaemia: Presence of methaemoglobin (oxidized haemoglobin) in the blood in greater than normal proportion (#IUPAC)

methaemoglobin-forming substance: Substance capable of oxidising directly or indirectly the iron(II) in haemoglobin to iron(III) to form methaemoglobin, a derivative of haemoglobin that cannot transport oxygen (#IUPAC)

microalbuminuria: Chronic presence of albumin in slight excess in urine (#IUPAC)

microcosm: Artificial test system that simulates major characteristics of the natural environment for the purposes of ecotoxicological assessment: such a system would commonly have a terrestrial phase, with substrate, plants and herbivores, and an aquatic phase, with vertebrates, invertebrates and plankton. The term "mesocosm" implies a more complex and larger system than the term "microcosm" but the distinction is not clearly defined
SN experimentalmodel ecosystem (#IUPAC)

micromercurialism: Effects of exposure to mercury detected at the lowest exposure levels producing a measurable reaction
RT mercurialism (#IUPAC)

microsome: Artefactual spherical particle, not present in the living cell, derived from pieces of the endoplasmic reticulum present in homogenates of tissues or cells: microsomes sediment from such homogenates when centrifuged at 100 000 g and higher: the microsomal fraction obtained in this way is often used as a source of mono-oxygenase enzymes
RT cytochrome P-420, cytochrome P-448, cytochrome P-450, endoplasmic reticulum, mono-oxygenase, phase 1 reactions (#IUPAC)

micturitic: See SN diuretic (#IUPAC)

Migration: Moving from one location to another (#ATSDR)

Minimal risk level (MRL): An ATSDR estimate of daily human exposure to a hazardous substance at or below which that substance is unlikely to pose a measurable risk of harmful (adverse), noncancerous effects. MRLs are calculated for a route of exposure (inhalation or oral) over a specified time period (acute, intermediate, or chronic). MRLs should not be used as predictors of harmful (adverse) health effects see reference dose. (#ATSDR)

Minamata disease: Neurological disease caused by ingestion of methylmercury-contaminated fish, first seen at Minamata Bay in Japan (#IUPAC)

mineralization: Complete conversion of organic substances to inorganic derivatives (#IUPAC)

minimum lethal concentration (LCmin): Lowest concentration of a toxic substance in an environmental medium that kills individual organisms or test species under a defined set of conditions
SN lowest lethal concentration found
WHO, 1979 (#IUPAC)

minimum lethal dose (LDmin): Lowest amount of a substance that, when introduced into the body, may cause death to individual species of test animals under a defined set of conditions (#IUPAC)

miosis: Abnormal contraction of the pupil of the eye to less than 2 mm. Alternative spelling (obsolete): meiosis (#IUPAC)

miscible: Liquid substances capable of mixing without separation into two phases; refers to liquid mixtures (#IUPAC)

mitochondrion: Eukaryote cytoplasmic organelle that is bounded by an outer membrane and an inner membrane; the inner membrane has folds called cristae that are the centre of ATP synthesis in oxidative phosphorylation in the animal cell and supplement ATP synthesis by the chloroplasts in photosynthetic cells. The mitochondrial matrix within the inner membrane contains ribosomes, many oxidative enzymes, and a circular DNA molecule that carries the genetic information for a number of these enzymes (#IUPAC)

mitogen: Substance that induces lymphocyte transformation or, more generally, mitosis and cell proliferation
RT transformation (#IUPAC)

mitosis: Process by which a cell nucleus divides into two daughter nuclei, each having the same genetic complement as the parent cell: nuclear division is usually followed by cell division
After Nagel et al. (eds), 1991 (#IUPAC)

mixed function oxidase: See SN mono-oxygenase (#IUPAC)

modifying factor (MF): As used by the USEPA, uncertainty factor that is greater than zero and less than, or equal to 10; the magnitude of the factor depends upon the professional assessment of scientific uncertainties of a study or database not explicitly treated with the standard uncertainty factors (for example the completeness of the overall database and the number of animals tested); the default value for the factor is 1
BT uncertainty factor
IRIS, 1986 (#IUPAC)

molluscicide: Substance intended to kill molluscs
SN limacide (#IUPAC)

monitoring: Continuous or repeated observation, measurement, and evaluation of health and/or environmental or technical data for defined purposes, according to prearranged schedules in space and time, using comparable methods for sensing and data collection. Evaluation requires comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and adverse effects
NT ambient monitoring, biological effect monitoring, biological monitoring, environmental monitoring, health surveillance, personal monitoring.
After Berlin, Yodaiken, and Henman,1984; WHO, 1980; Zielhuis and Henderson, 1986 (#IUPAC)

monoclonal: Pertaining to a specific protein from a single clone of cells, all molecules of this protein being the same (#IUPAC)

monoclonal antibody: Antibody produced by cloned cells derived from a single lymphocyte
BT antibody
RT[ polyclonal antibody|http://sis.nlm.nih.gov/enviro/glossaryp.html#polyclonalantibody] (#IUPAC)

mono-oxygenase: Enzyme that catalyses reactions between an organic compound and molecular oxygen in which one atom of the oxygen molecule is incorporated into the organic compound and one atom is reduced to water; involved in the metabolism of many natural and foreign compounds giving both unreactive products and products of different or increased toxicity from that of the parent compound: such enzymes are the main catalysts of phase 1 reactions in the metabolism of xenobiotics by the endoplasmic reticulum or by preparations of microsomes
SN mixed function oxidase
RT cytochrome P-420, cytochrome P-448, cytochrome P-450, endoplasmic reticulum, microsome, phase 1 reactions (#IUPAC)

morbidity: Any departure, subjective or objective, from a state of physiological or psychological well-being: in this sense, "sickness", "illness", and "morbid condition" are similarly defined and synonymous. The WHO Expert Committee on Health Statistics noted in its Sixth Report (1959) that morbidity could be measured in terms of three units:
1. Proportion of persons who were ill
2. The illnesses (periods or spells of illnesses) that these persons experienced
3. The duration (days, weeks, etc.) of these illnesses
NT disease
Last, 1988 (#IUPAC)

morbidity rate: Term used loosely to refer to incidence or prevalence rates of disease
IPCS, 1978 (International)
mordant: Substance that fixes a dyestuff in or on a material by combining with the dye to form an insoluble compound, used to fix or intensify stains in a tissue or cell preparation (#IUPAC)

mortality: Death as studied in a given population or subpopulation. The word mortality is often used incorrectly instead of mortality rate
IPCS, 1978 (#IUPAC)

mortality rate: See SN death rate (#IUPAC)

mortality study: Investigation dealing with death rates or proportion of deaths attributed to specific causes as a measure of response
IPCS, 1978 (#IUPAC)

multigeneration study:
1. Toxicity test in which two to three generations of the test organism are exposed to the substance being assessed
2. Toxicity test in which only one generation is exposed and effects on subsequent generations are assessed
multiple (or multiphasic) screening: Procedure that has evolved by combining single screening tests, and is the logical corollary of mass screening. Where much time and effort have been spent by a population in attending for a single test such as mass radiography, it is natural to consider the economy of offering other tests at the same time. Multiple (or multiphasic) screening implies the administration of a number of tests, in combination, to large groups of people
BT screening
WHO, 1989a (#IUPAC)

multistage cluster sampling: Cluster sampling with more than two stages, each sampling being made on aggregates (or clusters) in which the clusters already obtained by the preceding sampling have been divided.
ISO, 1977 (#IUPAC)

multistage model: Dose-response model for cancer death estimation of the form
P(d) = 1 - exp2^ + ... + q~k~d^k^)
where P(d) is the probability of cancer death from a continuous dose rate, d, the q's are constants, and k is the number of dose groups (or, if less than the number of dose groups, k is the number of biological stages believed to be required in the carcinogenesis process). With the multistage model, it is assumed that cancer is initiated by cell mutations in a finite series of steps. A one-stage model is equivalent to a one-hit model (#IUPAC)

multistage sampling: Type of sampling in which the sample is selected by stages, the sampling units at each stage being subsampled from the larger units chosen at the previous stage
ISO, 1977 (#IUPAC)

murine: Of or belonging to the family of rats and mice (Muridae) (#IUPAC)

mutagen: Any substance that can induce heritable changes (mutations) of the genotype in a cell as a consequence of alterations or loss of genes or chromosomes (or parts thereof) (#IUPAC)

mutagenesis: Introduction of heritable changes (mutations) of the genotype in a cell as a consequence of alterations or loss of genes or chromosomes (or parts thereof)
After Nagel et al. (eds), 1991 (#IUPAC)

mutagenicity: Ability of a physical, chemical, or biological agent to induce heritable changes (mutations) in the genotype in a cell as a consequence of alterations or loss of genes or chromosomes (or parts thereof) (#IUPAC)

mutation: Any relatively stable heritable change in genetic material that may be a chemical transformation of an individual gene ( gene or point mutation), altering its function, or a rearrangement, gain or loss of part of a chromosome, that may be microscopically visible (chromosomal mutation); mutation can be either germinal and inherited by subsequent generations, or somatic and passed through cell lineage by cell division
RT chromosome, gene
RT clastogenesis, genotoxicity (#IUPAC)

myasthenia: Muscular weakness (#IUPAC)

mycotoxin: Toxin produced by a fungus (#IUPAC)

mydriasis: Extreme dilation of the pupil of the eye, either as a result of normal physiological response or in response to a chemical exposure (#IUPAC)

myelosuppression: Reduction of bone marrow activity leading to a lower concentration of platelets, red cells and white cells in the blood (#IUPAC)


1. Nonspecific usage - an agent that produces insensibility or stupor
2. Specific usage - an opioid, any natural or synthetic drug that has morphine-like actions

NAS: See "National Academy of Sciences." (#Glossary)

National Academy of Sciences (NAS): NAS is a private, nonprofit corporation established by Congress to investigate and report on science and technology at the request of the federal government. The National Research Council (NRC) is a part of the NAS and has reported on public health problems such as chemical contamination of drinking water. (#Glossary)

National Ambient Air Quality Standards (NAAQS): Standards established by the US Environmental Protection Agency that apply for outside air throughout the country.(1) (#CEHN)

National Exposure Registry: A listing of persons exposed to hazardous substances. This listing is composed of chemical-specific subregistries. The primary purpose of the registry program is to create a large database of similarly exposed persons. This database is to be used to facilitate epidemiology research in ascertaining adverse health effects of persons exposed to low levels of chemicals over a long period.(2) (#CEHN)

National Institute of Environmental Health Sciences: The NIEHS tries to reduce human illness from environmental causes by understanding environmental factors, individual susceptibility and age. The NIEHS conducts biomedical research programs, prevention and intervention efforts, and education (#Glossary)

National Institute for Occupational Safety and Health (NIOSH): NIOSH, part of the Centers for Disease Control, conducts research on worker safety and health and recommends standards for worker protection to OSHA. For example, NIOSH recommends guidelines for workplace exposure to hazardous substances and has published criteria documents on many chemicals. (#Glossary)

National Institutes of Health (NIH): NIH, part of the U.S. Department of Health and Human Services, conducts scientific research into the causes, prevention and cure of diseases. For example, the National Cancer Institute (part of NIH) studies how some environmental chemicals cause cancer. Many other diseases, some related to chemical exposure, are also under study at NIH. (#Glossary)

National Priorities List for Uncontrolled Hazardous Waste Sites (National Priorities List or NPL): EPA 's list of the most serious uncontrolled or abandoned hazardous waste sites in the United States. The NPL is updated on a regular basis. (#ATSDR)

National Research Council: See "National Academy of Sciences." (#Glossary)

National Toxicology Program (NTP):
Part of the Department of Health and Human Services. NTP develops and carries out tests to predict whether a chemical will cause harm to humans (#ATSDR)

natriuretic: Substance increasing the rate of excretion of sodium ion in the urine (#IUPAC)

natural occurrence: Presence of a substance in nature, as distinct from presence resulting from inputs from human activities. The contamination of the natural environment by some man-made compounds may be so widespread that it is practically impossible to get access to biota with a truly natural level; only "normal" levels can be measured, those which are usually prevalent in places where there is no obvious local contamination (#IUPAC)

necropsy: See SN autopsy
RT biopsy (#IUPAC)

1. Mass death of areas of tissue or bone surrounded by healthy areas
2. Morphological changes that follow cell death, characterized most frequently by nuclear changes
negligible risk:
1. Probability of adverse effects occurring that can reasonably be described as trivial
2. Probability of adverse effects occurring that is so low that it cannot be reduced appreciably by increased regulation or investment of resources
RT acceptable risk, accepted risk, risk de minimis (#IUPAC)

nematocide: Substance intended to kill nematodes (#IUPAC)

neonate: Infant during the first 4 weeks of postnatal life; for statistical purposes some scientists have defined the period as the first 7 days (#IUPAC)

neoplas/ia, -m: New and abnormal formation of tissue as a tumour or growth by cell proliferation that is faster than normal and continues after the initial stimulus (info) that initiated the proliferation has ceased
PS tumour
RT hyperplasia, metaplasia (#IUPAC)

nephritis: Inflammation of the kidney, leading to kidney failure, usually accompanied by proteinuria, haematuria, oedema, and hypertension (#IUPAC)

nephrotoxic: Chemically harmful to the cells of the kidney (#IUPAC)

neural: Pertaining to a nerve or to the nerves (#IUPAC)

neuron(e): Nerve cell, the morphological and functional unit of the central and peripheral nervous systems (#IUPAC)

neuropathy: Any disease of the central or peripheral nervous system (#IUPAC)

neurotoxic/ adj., -ity n.: Able to produce chemically an adverse effect on the nervous system: such effects may be subdivided into two types
1. Central nervous system effects (including transient effects on mood or performance and pre-senile dementia such as Alzheimer's disease)
2. Peripheral nervous system effects (such as the inhibitory effects of organophosphorus compounds on synaptic transmission)

NIEHS: National Institute of Environmental Health Sciences (#Glossary)

NIH: See "National Institutes of Health." (#Glossary)

NIOSH: See "National Institute for Occupational Safety and Health." (#Glossary)

nitrification: Sequential oxidation of ammonium salts to nitrite and nitrate by micro-organisms (#IUPAC)

no acceptable daily intake allocated: This expression is applicable to a substance for which the available information is not sufficient to establish its safety, or when the specifications for identity and purity are not adequate, or when the available data show that the substance is hazardous and should not be used: the basis for the use of the expression should be determined before action is taken; in the first two cases above, not being able to allocate an ADI does not mean that the substance is unsafe

RT acceptable daily intake (International)
no apparent public health hazard: A category used in ATSDR's public health assessments for sites where human exposure to contaminated media might be occurring, might have occurred in the past, or might occur in the future, but where the exposure is not expected to cause any harmful health effects. (ATSDR)
n-octanol-water partition coefficient: See SN octanol-water partition coefficient (#IUPAC)

nodule: Small node or boss that is solid and can be detected by touch (#IUPAC)

no effect level (NEL): Maximum dose (of a substance) that produces no detectable changes under defined conditions of exposure. At present, this term tends to be substituted by no-observed-adverse-effect-level (NOAEL) or no-observed-effect-level (NOEL)
RT adverse effect, no-observed-adverse-effect-level (NOAEL), no-observed-effect-level (NOEL) (#IUPAC)

non-attainment area: Area that does not meet one or more of the National Ambient Air Quality Standards for the criteria pollutants designated in the Clean Air Act.(1) (#CEHN)

non-bioenvironmental transformation: Change in the chemical or physical nature of a substance occurring as a result of physicochemical conditions and independent of any biological system (#IUPAC)

non-effective dose: Amount of a substance that has no effect on the organism. It is lower than the threshold of harmful effect and is estimated while establishing the threshold of harmful effect
SN subthreshold dose
RT threshold (#IUPAC)

non-occupational exposure: Environmental exposure outside the workplace to substances that are otherwise associated with particular work environments and/or activities and processes that occur there (#IUPAC)

non-target organism: Organism affected by a pesticide although not the intended object of its use (#IUPAC)

no-observed-adverse-effect-level (NOAEL): Greatest concentration or amount of a substance, found by experiment or observation, which causes no detectable adverse alteration of morphology, functional capacity, growth, development, or life span of the target organism under defined conditions of exposure
WHO, 1979
RT adverse effect (#IUPAC)

no-observed-effect-level (NOEL): Greatest concentration or amount of a substance, found by experiment or observation, that causes no alterations of morphology, functional capacity, growth, development, or life span of target organisms distinguishable from those observed in normal (control) organisms of the same species and strain under the same defined conditions of exposure
RT adverse effect (International)
no public health hazard: A category used in ATSDR's public health assessment documents for sites where people have never and will never come into contact with harmful amounts of site-related substances (#ATSDR)

no-response level: Maximum dose of a substance at which no specified response is observed in a defined population and under defined conditions of exposure
IRPTC, 1982 (#IUPAC)

nosocomial: Associated with a hospital or infirmary, especially used of diseases that may result from treatment in such an institution
BT iatrogenic (#IUPAC)

noxious substance: See SN harmful substance (International)
NPL: see National Priorities List for Uncontrolled Hazardous Waste Sites (ATSDR)
NRC: See "National Academy of Sciences." (#Glossary)

nuisance threshold: Lowest concentration of an air pollutant that can be considered objectionable
IRPTC, 1982
RT odour threshold, pollutant (#IUPAC)

nutritional table method: Procedure for evaluating the dietary intake of a large number of people. The accuracy of the method depends on the accuracy with which records of the food consumption can be established and the accuracy of the nutritional tables specifying the concentration of various nutrients, vitamins, essential, and non-essential substances including pesticide residues. For each record of quantity of food consumed during a certain time period, the daily intake of the substance in question is calculated by multiplying the substance concentration in the food item (as obtained from the nutritional table) by the quantity of food consumed and dividing by the time of observation
WHO, 1979 (#IUPAC)

nystagmus: Involuntary, rapid, rhythmic movement (horizontal, vertical, rotary, mixed) of the eyeball, usually caused by a disorder of the labyrynth of the inner ear or a malfunction of the central nervous system (#IUPAC)


objective environment: Actual physical, chemical, and social environment as described by objective measurements, such as noise levels in decibels and concentrations of air pollutants
WHO, 1979 (#IUPAC)

occupational environment: Surrounding conditions at a workplace (#IUPAC)

occupational exposure: Experience of substances, intensities of radiation etc. or other conditions while at work (#IUPAC)

occupational exposure limit (OEL): Regulatory level of exposure to substances, intensities of radiation etc. or other conditions, specified appropriately in relevant government legislation or related codes of practice (#IUPAC)

occupational exposure standard (OES):
1. Level of exposure to substances, intensities of radiation etc. or other conditions considered to represent specified good practice and a realistic criterion for the control of exposure by appropriate plant design, engineering controls, and, if necessary, the addition and use of personal protective clothing.
2. In GBR, health-based exposure limit defined under COSHH Regulations as the concentration of any airborne substance, averaged over a reference period, at which, according to current knowledge, there is no evidence that it is likely to be injurious to employees, if they are exposed by inhalation, day after day, to that concentration, and set on the advice of the HSE Advisory Committee on Toxic Substances.
occupational hygiene: Identification, assessment and control of physicochemical and biological factors in the workplace that may affect the health or well-being of those at work and in the surrounding community (International)
Occupational Safety and Health Administration (OSHA): OSHA, part of the U.S. Department of Labor, enforces federal laws that protect worker safety and health, such as maintaining standards for occupational exposure to chemicals, training employees and keeping records of chemical exposures (#Glossary)

octanol-water partition coefficient (POW, KOW): Measure of lipophilicity by determination of the equilibrium distribution between octan-1-ol and water, as used in pharmacological studies and in the assessment of environmental fate and transport of organic chemicals.
RT lipophilicity, lgKOW, lgPOW (#IUPAC)

ocular: Pertaining to the eye (#IUPAC)

odds: Ratio of the probability of occurrence of an event to that of non-occurrence, or the ratio of the probability that something is so, to the probability that it is not so
Last, 1988 (#IUPAC)

odds ratio: Quotient obtained by dividing one set of odds by another. The term "odds" or "odds ratio" is defined differently according to the situation under discussion. Consider the following notation for the distribution of a binary exposure and a disease in a population or a sample
Exposed Nonexposed
Disease a B
No disease c D

The odds ratio (cross-product ratio) is ad/(bc).
1. The exposure-odds ratio for a set of case control data is the ratio of the odds in favour of exposure among the cases (a/b) to the odds in favour of exposure among non-cases (c/d). This reduces to ad/(bc). With incident cases, unbiased subject selection, and a "rare" disease (say, under 2 % cumulative incidence rate over the study period), ad/(bc)is an approximate estimate of the risk ratio. With incident cases, unbiased subject selection, and density sampling of controls, ad/(bc) is an estimate of the ratio of the person-time incidence rates (forces of morbidity) in the exposed and unexposed. No rarity assumption is required
2. The disease-odds (rate-odds) ratio for a cohort or cross section is the ratio of the odds in favour of disease among the exposed population (a/c) to the odds in favour of disease among the unexposed (b/d). This reduces to ad/(bc) and hence is equal to the exposure-odds ratio for the cohort or cross section
3. The prevalence-odds refers to an odds ratio derived cross sectionally, as, for example, an odds ratio derived from studies of prevalent (rather than incident) cases
4. The risk-odds ratio is the ratio of the odds in favour getting disease, if exposed, to the odds in favour of getting disease if not exposed. The odds ratio derived from a cohort study is an estimate
SN cross-product ratio, relative odds
Last, 1988
odour threshold: In principle, the lowest concentration of an odorant that can be detected by a human being: in practice, a panel of "sniffers" is used, and the threshold taken as the concentration at which 50% of the panel can detect the odorant (although some workers have also used 100% thresholds) (#IUPAC)

oedema: Presence of abnormally large amounts of fluid in intercellular spaces of body tissues (#IUPAC)

olfactometer: Apparatus for testing the power of the sense of smell (#IUPAC)

oliguria: Excretion of a diminished amount of urine in relation to fluid intake (#IUPAC)

oncogene: Gene that can cause neoplastic transformation of a cell; oncogenes are slightly changed equivalents of normal genes known as proto-oncogenes
RT transformation (#IUPAC)

oncogenesis: Production or causation of tumors

one-hit model: Dose-response model of the form
P(d) = 1 - exp(-bd)
where P(d) is the probability of cancer death from a continuous dose rate (d) and b is a constant. The one-hit model is based on the concept that a tumour can be induced after a single susceptible target or receptor has been exposed to a single effective dose unit of an agent.
IRIS, 1986 (#IUPAC)

onycholysis: Loosening or detachment of the nail from the nailbed following some destructive process

oogenesis: Process of formation of the ovum (plural ova), the female gamete (#IUPAC)

operon: Complete unit of gene expression and regulation, including structural genes, regulator gene(s) and control elements in DNA recognized by regulator gene product(s) (#IUPAC)

ophthalmic: Pertaining to the eye (#IUPAC)

oral toxicity: Ability of a pesticide to cause injury when ingested.(1) (#CEHN)

organ dose: Amount of a substance or physical agent (radiation) absorbed by an organ (#IUPAC)

organelle: Microstructure or separated compartment within a cell that has a specialized function, for example ribosome, peroxisome, lysosome, Golgi apparatus, mitochondrion, nucleolus, nucleus
After Nagel et al. (eds), 1991 (#IUPAC)

organic: Generally considered as originating from plants or animals, and made primarily of carbon and hydrogen. Scientists use the term organic to mean those chemical compounds which are based on carbon. (#Glossary)

organic carbon partition coefficient (KOC): Measure of the tendency for organic substances to be adsorbed by soil and sediment, expressed as:
(mg substance adsorbed)/(kg organic carbon) KOC = --------------------------------------------
(mg substance dissolved)/(litre of solution) The KOC is substance-specific and is largely independent of soil properties
USEPA, 1986 (#IUPAC)

organoleptic: Involving an organ, especially a sense organ as of taste, smell or sight (#IUPAC)

OSHA: See Occupational Safety and Health Administration

osteo-: Prefix meaning pertaining to bone (#IUPAC)

osteodystrophy: Abnormal development of bone (#IUPAC)

osteogenesis: Formation or development of bone (#IUPAC)

osteoporosis: Significant decrease in bone mass with increased porosity and increased tendency to fracture (#IUPAC)

ovicide: Substance intended to kill eggs (#IUPAC)

ozone depletion: Destruction of the stratospheric ozone layer which shields the earth from ultraviolet radiation harmful to life. This destruction of ozone is caused by the breakdown of certain chlorine and/or-bromine containing compounds (chlorofluorocarbons or halons), which break down when they reach the stratosphere and then catalytically destroy ozone molecules.(1) (#CEHN)


1. Unduly rapid or throbbing heartbeat that is noted by a patient; it may be regular or irregular.
2. Undue awareness by a patient of a heartbeat that is otherwise normal.
paraesthesia: Abnormal sensation, as burning or prickling (#IUPAC)

paralysis: Loss or impairment of motor function (#IUPAC)

para-occupational exposure:
1. Exposure of a worker's family to substances carried from the workplace to the home.
2. Exposure of visitors to substances in the workplace.
parasympatholytic: Producing effects resembling those caused by interruption of the parasympathetic nerve; also called anticholinergic (#IUPAC)

parasympathomimetic: Producing effects resembling those caused by stimulation of the parasympathetic nervous system; also called cholinomimetic (#IUPAC)

parenteral dosage: Method of introducing substances into an organism avoiding the gastrointestinal tract (subcutaneously, intravenously, intramuscularly etc.) (#IUPAC)

paresis: Slight or incomplete paralysis (#IUPAC)

permeability: The property of permitting liquids or gases to pass through. A highly permeable soil, such as sand, allows a liquid to pass through quickly. Clay has a low permeability (#Glossary)

partition coefficient: Ratio of the distribution of a substance between two phases when the heterogeneous system (of two phases) is in equilibrium; the ratio of concentrations (or, strictly speaking, activities) of the same molecular species in the two phases is constant at constant temperature. The partition coefficients most frequently used in acute toxicology are
lipid/water and octan-1-ol/water distributions.

passive smoking: Inhalation of sidestream smoke by people who do not smoke themselves.
See RT sidestream smoke (#IUPAC)

pathogens: Microorganisms that can cause disease in other organisms or in humans, animals and plants (e.g., bacteria, viruses, or parasites) found in sewage, in runoff from farms or rural areas populated with domestic and wild animals, and in water used for swimming. Fish and shellfish contaminated by pathogens, or the contaminated water itself, can cause serious illness.(1) (#CEHN)

peak daily average concentration of an air pollutant: See SN maximum average daily concentration of an atmospheric pollutant (#IUPAC)

perceived environment or risk: See SN subjective environment.
RT risk perception (#IUPAC)

percutaneous: Through the skin following application on the skin (#IUPAC)

performance standards: (1) Regulatory requirements limiting the concentrations of designated organic compounds, particulate matter, and hydrogen chloride in emissions from incinerators. (2) Operating standards established by EPA for various permitted pollution control systems, asbestos inspections, and various program operations and maintenance requirements.(1) (#CEHN)

perinatal: Relating to the period shortly before and after birth; from the twentieth to the twenty-ninth week of gestation to one to four weeks after birth (#IUPAC)

peritoneal dialysis: Method of artificial detoxication in which a toxic substance from the body is transferred into liquid that is instilled into the peritoneum. Thus, the employment of the peritoneum surrounding the abdominal cavity as a dialysing membrane for the purpose of removing waste products or toxins accumulated as a result of renal failure (#IUPAC)

permissible exposure limit (PEL): Recommendation by US OSHA for TWA concentration that must not be exceeded during any 8-hour work shift of a 40h working week.
RT maximum allowable concentration, threshold limit value, time weighted average concentration (TWAC), exposure limit (#IUPAC)

peroxisome: Organelle, similar to a lysosome, characterized by its content of catalase (EC, peroxidase (EC and other oxidative enzymes (International)

persistence: Attribute of a substance that describes the length of time that the substance remains in a particular environment before it is physically removed or chemically or biologically transformed.
IRPTC, 1982
RT recalcitrance (#IUPAC)

personal monitoring: Type of environmental monitoring in which an individual's exposure to a substance is measured and evaluated: this is normally carried out using a personal sampler.
BT monitoring.
RT personal sampler (#IUPAC)

personal protective device (PPD): See SN personal protective equipment (PPE).
SN individual protective device (IPD) (#IUPAC)

personal protective equipment (PPE): Equipment (clothing, gloves, hard hat, respirator and so on) worn by an individual to prevent exposure to a potentially toxic substance.
SN individual protective device (IPD), personal protective device (PPD). (#IUPAC)

personal sampler: Compact, portable instrument for individual air sampling, measuring, or both, the content of a harmful substance in the respiration zone of a working person.
SN individual monitor.
IRPTC, 1982 (#IUPAC)

pest: Organism that may harm public health, that attacks food and other materials essential to mankind, or otherwise affects human beings adversely (#IUPAC)

pesticide: Strictly a substance intended to kill pests: in common usage, any substance used for controlling, preventing, or destroying animal, microbiological or plant pests.
NT fungicides, herbicides, insecticides (#IUPAC)

pesticide residue: Pesticide residue is any substance or mixture of substances in food for man or animals resulting from the use of a pesticide and includes any specified derivatives, such as degradation and conversion products, metabolites, reaction products and impurities considered to be of toxicological significance (#IUPAC)

pesticide tolerance: The amount of pesticide residue allowed by law to remain in or on a harvested crop. EPA seeks to set these levels well below the point where the compounds might be harmful to consumers.(5) (#CEHN)

phagocytosis: Engulfing and digestion of micro-organisms, other cells, and foreign particles by cells such as phagocytes.
RT macrophage (#IUPAC)

pharmaceuticals: Drugs, medical products, medicines, or medicaments (#IUPAC)

pharmacodynamics: Process of interaction of pharmacologically active substances with target sites, and the biochemical and physiological consequences leading to therapeutic or adverse effects.
RT adverse effect, target, toxicodynamics (#IUPAC)

pharmacogenetics: Study of the influence of hereditary factors on the effects of drugs on individual organisms.
PS toxicogenetics.
RT ecogenetics, polymorphism (#IUPAC)

pharmacokinetics: Process of the uptake of drugs by the body, the biotransformation they undergo, the distribution of the drugs and their metabolites in the tissues, and the elimination of the drugs and their metabolites from the body. Both the amounts and the concentrations of the drugs and their metabolites are studied. The term has essentially the same meaning as toxicokinetics, but the latter term should be restricted to the study of substances other than drugs.
BT chemobiokinetics.
PS toxicokinetics.
RT biotransformation, pharmacokinetics (#IUPAC)

pharynx: Throat, the part of the digestive tract between the oesophagus below and the mouth and nasal cavities above and in front (#IUPAC)

phase 1 reaction (of biotransformation): Enzymic modification of a substance by oxidation, reduction, hydrolysis, hydration, dehydrochlorination or other reactions catalysed by enzymes of the cytosol, of the endoplasmic reticulum (microsomal enzymes) or of other cell organelles.
BT biotransformation.
RT cytochrome P-420, cytochrome P-448, cytochrome P-450, microsome, phase 2 reaction, phase 3 reaction (#IUPAC)

phase 2 reaction (of biotransformation): Binding of a substance, or its metabolites from a phase 1 reaction, with endogenous molecules (conjugation), making more water-soluble derivatives that may be excreted in the urine or bile.
BT biotransformation.
RT conjugate, phase 1 reaction, phase 3 reaction (#IUPAC)

phase 3 reaction (of biotransformation): Further metabolism of conjugated metabolites produced by phase 2 reactions: it may result in the production of toxic derivatives.
BT biotransformation.
RT conjugate, phase 1 reaction, phase 2 reaction (#IUPAC)

phenotype: The observable structural and functional characteristics of an organism determined by its genotype and modulated by its environment.
Nagel et al. (eds), 1991
RT genotype (#IUPAC)

pheromone: Substance used in olfactory communication between organisms of the same species eliciting a change in sexual or social behaviour.
SN ectohormone, feromone (#IUPAC)

photochemical smog: Air pollution caused by chemical reactions of various pollutants emitted from different sources.(1) (#CEHN)

photo-irritation: Inflammation of the skin caused exposure to light, especially that due to metabolites formed in the skin by photolysis.
RT photosensitization, phototoxicity (#IUPAC)

photo-oxidant: Substance able to cause oxidation when exposed to light of the appropriate wavelength (#IUPAC)

photophobia: Abnormal visual intolerance of light (#IUPAC)

photosensitization: Allergic reaction due to a metabolite formed by the influence of light (#IUPAC)

phototoxicity: Adverse effects produced by exposure to light energy, especially those produced in the skin (#IUPAC)

Physiologically Based Pharmacokinetic model (PBPK model): A computer model that describes what happens to a chemical in the body. This model describes how the chemical gets into the body, where it goes in the body, how it is changed by the body, and how it leaves the body. (#ATSDR)

phytotoxic: Poisonous to plants; inhibiting plant growth (International)
pica: A craving to eat nonfood items, such as dirt, paint chips, and clay. Some children exhibit pica-related behavior (#ATSDR)

picocuries per liter (pCi/L): A unit of measure for levels of radon gas.(1) (CEHN)
piscicide: Substance intended to kill fish (#IUPAC)

1. Fluid component of blood in which the blood cells and platelets are suspended.
SN blood plasma.
2. Fluid component of semen produced by the accessory glands, the seminal vesicles, the prostate, and the bulbo-urethral glands.
3. Cell substance outside the nucleus.
SN cytoplasm.
plasma half-life: See SN elimination half-life (#IUPAC)

plasmapheresis: Removal of blood from the body and centrifuging it to obtain plasma and packed red blood cells: the blood cells are resuspended in a physiologically compatible solution (usually type-specific fresh frozen plasma or albumin) and returned to the donor or injected into a patient who requires blood cells rather than whole blood. (#IUPAC)

plasmid: Autonomous self-replicating extra-chromosomal circular DNA molecule (#IUPAC)

pleura: Lining of the lung (#IUPAC)

ploidy: Term indicating the number of sets of chromosomes present in an organism.
RT diploid, haploid (#IUPAC)

plumbism: Chronic poisoning caused by absorption of lead or lead salts.
SN saturnism (International)
plume: A volume of a substance that moves from its source to places farther away from the source. Plumes can be described by the volume of air or water they occupy and the direction they move. For example, a plume can be a column of smoke from a chimney or a substance moving with groundwater. (#ATSDR)

pneumoconiosis: Usually fibrosis of the lungs that develops owing to (prolonged) inhalation of inorganic or organic dusts. Cause-specific types of pneumoconiosis:
1.anthracosis From coal dust.
2.asbestosis From asbestos dust.
3.byssinosis From cotton dust.
4.siderosis From iron dust.
5.silicosis From silica dust.
6.stannosis From tin dust.
IRPTC, 1982; Parkes, 1982 (#IUPAC)

pneumonitis: Inflammation of the lung (#IUPAC)\\\\
po: Per os - Latin for by mouth (#IUPAC)

point mutation: Reaction that changes a single base pair in DNA (International)
point of exposure: The place where someone can come into contact with a substance present in the environment see exposure pathway (#ATSDR)

point source: Single emission source in a defined location.
RT area source (#IUPAC)

poison: Substance that, taken into or formed within the organism, impairs the health of the organism and may kill it.
SN toxic substance (#IUPAC)

poison-bearing: Containing a poison (#IUPAC)

poisoning: Morbid condition produced by a poison
SN intoxication (#IUPAC)

pollutant: Any undesirable solid, liquid or gaseous matter in a solid, liquid or gaseous environmental medium: "undesirability" is often concentration-dependent, low concentrations of most substances being tolerable or even essential in many cases. For the meaning of "undesirable" in air pollution contexts, see "pollution". A primary pollutant is one emitted into the atmosphere, water, sediments or soil from an identifiable source. A secondary pollutant is a pollutant formed by chemical reaction in the atmosphere, water, sediments, or soil.
PS contaminant.
RT pollution,secondary pollutant.
After WHO, 1980 (#IUPAC)

pollution: Introduction of pollutants into a solid, liquid, or gaseous environmental medium, the presence of pollutants in a solid, liquid, or gaseous environmental medium, or any undesirable modification of the composition of a solid, liquid or gaseous environmental medium. In the context of air pollution, an undesirable modification is one that has injurious or deleterious effects.
RT contaminant,pollutant.
ISO, 1979; WHO, 1989a (#IUPAC)

polyclonal antibody: Antibody produced by a number of different cell types.
BT antibody.
RT monoclonal antibody (#IUPAC)

polydipsia: Chronic excessive thirst (#IUPAC)

polymorphism (polymorphia) in metabolism: Interindividual variations in metabolism of endo- and exogenous compounds due to genetic influences, leading to enhanced side effects or toxicity of drugs (for example, poor versus fast metabolizers) or to different clinical effects (metabolism of steroid hormones).
RT ecogenetics, pharmacogenetics, toxicogenetics (#IUPAC)

polyuria: Excessive production and discharge of urine (#IUPAC)

population: In statistics, the totality of items under consideration. A clearly defined part of a population is called a subpopulation. In the case of a random variable, the probability distribution is considered as defining the population of that variable. The term "population segment" is sometimes used as a synonym for subpopulation.
WHO, 1989a (#IUPAC)

population at risk: Number of persons who can and may develop an adverse health effect and who are potentially exposed to a risk factor under study: for example, all people in a population who have not developed immunity to an infectious disease are at risk of developing that disease if they are exposed to it. People already having chronic disease are excluded from the population at risk in studies of the incidence of the disease.
After WHO, 1979 (#IUPAC)

population critical concentration (PCC): Concentration of a substance in the critical organ at which a specified percentage of the exposed population has reached the individual critical organ concentration. The percentage indicated by PCC-10 for 10%, PCC-50 for 50% etc. (similar to the use of the term LD50).
Kjellstrom et al., 1984 (#IUPAC)

population effect: Absolute number or incidence rate of cases occurring in a group of people (#IUPAC)

population risk: See SN societal risk (#IUPAC)

pollutant Standard Index (PSI): Measure of adverse health effects of air pollution levels in major cities.(1) (#CEHN)

porphyria: Disturbance of porphyrin metabolism characterized by increased formation, accumulation, and excretion of porphyrins and their precursors (#IUPAC)

posology: Study of dose in relation to the physiological factors that may influence response such as age of the exposed organisms.
Brown, 1988 (#IUPAC)

potable water: Water that is safe for drinking and cooking.(1) (#CEHN)

potency: Expression of chemical or medicinal activity of a substance as compared to a given or implied standard or reference (#IUPAC)

Potentially Responsible Party (PRP): A company, government, or person legally responsible for cleaning up the pollution at a hazardous waste site under Superfund. There may be more than one PRP for a particular site (#ATSDR)

potentiation: Dependent action in which a substance or physical agent at a concentration or dose that does not itself have an adverse effect enhances the harm done by another substance or physical agent.
RT additive effect, antagonism, synergism (#IUPAC)

ppb: Parts per billion (#ATSDR)

ppm: Parts per million (#ATSDR)

practical certainty (of safety): Numerically specified low risk of exposure to a potentially toxic substance (for example, 1 in 106) or socially acceptable low risk of adverse effects from such an exposure applied to decision making
in regard to chemical safety.
RT risk,safety.
After Duffus, 1986 (#IUPAC)

precision: Measure for the reproducibility of measurements within a set, that is, of the scatter or dispersion of a set about its central value.
Gold, Loening, McNaught and Sehmi,1987 (#IUPAC)

precordial: Pertaining to the region over the heart and lower thorax (#IUPAC)

precursor: Substance from which another, usually more biologically active, substance is formed (#IUPAC)

predictive validity: Reliability of a measurement expressed in terms of its ability to predict the criterion: an example would be an academic aptitude test that was validated against subsequent academic performance.
Last, 1988 (#IUPAC)

predictive value: Percentage of positive results that are true positives or of negative results that are true negatives.
Galen and Gambino, 1975
RT sensitivity, specificity (#IUPAC)

Preliminary Site Assessment (PSA): A process followed by the [NYS Department of Environmental Conservation' (DEC) to determine if a site contains hazardous waste and its potential for harming the public health or environment. This process includes inspecting the site, sampling if needed, and taking physical or hydrological measurements as appropriate. (#Glossary)

preneoplastic: Before the formation of a tumour (#IUPAC)

prevalence: Number of instances of existing cases of a given disease or other condition in a given population at a designated time; sometimes used to mean prevalence rate. When used without qualification, the term usually refers to the situation at a specified point in time (point prevalence).
Last, 1988
RT incidence (#IUPAC)

prevalence rate (ratio): Total number of individuals who have an attribute or disease at a particular time (or during a particular period) divided by the population at risk of having the attribute or disease at this point in time or midway through the period.
Last, 1988
RT population at risk (#IUPAC)

prevalence survey: The measure of the current level of disease(s) or symptoms and exposures through a questionnaire that collects self-reported information from a defined population (#ATSDR)

prevention: Actions that reduce exposure or other risks, keep people from getting sick, or keep disease from getting worse (#ATSDR)

primary pollutant: See BT pollutant (#IUPAC)

primary protection standard: Accepted maximum level of a pollutant (or its indicator) in the target organism, or some part thereof, or an accepted maximum intake of a pollutant or nuisance into the target under specified circumstances.
WHO,1989a (#IUPAC)

probit: Probability unit obtained by adding 5 to the normal deviates of a standardized normal distribution of results from a dose response study: addition of 5 removes the complication of handling negative values. A plot of probit against the logarithm of dose or concentration gives a linear plot if the distribution of response is a logarithmic normal one. Estimates of the D50 and ED50 (or LC50 and EC50) can be obtained from this plot. (#IUPAC)

procarcinogen: Substance that has to be metabolized before it can induce malignant tumours (#IUPAC)

prokaryote: Unicellular organism, characterised by the absence of a membrane-enclosed nucleus. Prokaryotes include bacteria, blue-green algae and mycoplasmas.
RT eukaryote.
After Nagel et al. (eds), 1991 (#IUPAC)

promoter (in oncology): Agent that induces cancer when administered to an animal or human being who has been exposed to a cancer initiator.
RT initiator (#IUPAC)

prophage: Latent state of a phage genome in a lysogenic bacterium.
Nagel et al. (eds), 1991 (#IUPAC)

proportional mortality rate (ratio) (PMR): Number of deaths from a given cause in a specified time period, per 100 or per 1000 total deaths in the same time period: can give rise to misleading conclusions if used to compare mortality experience of populations with different causes of death.
Last, 1988 (#IUPAC)

prospective cohort study: See BT cohort study (#IUPAC)

proteinuria: Excretion of excessive amounts of protein (derived from blood plasma or kidney tubules) in the urine (#IUPAC)

protocol: The detailed plan for conducting a scientific procedure. A protocol for measuring a chemical in soil, water or air describes the way in which samples should be collected and analyzed (#Glossary)

pseudoadaptation: Apparent adaptation of an organism to changing conditions of the environment (especially chemical) associated with stresses in biochemical systems that exceed the limits of normal (homeostatic) mechanisms: essentially there is a temporary concealed pathology that later on can be manifested in the form of explicit pathological changes sometimes referred to as "decompensation."
RT compensation. (#IUPAC)

psychosis: Any major mental disorder characterized by derangement of the personality and loss of contact with reality (#IUPAC)

psychotropic: Exerting an effect upon the mind; capable of modifying mental activity (#IUPAC)

public availability session: An informal, drop-by meeting at which community members can meet one-on-one with ATSDR staff members to discuss health and site-related concerns (#ATSDR)

public comment period: An opportunity for the public to comment on agency findings or proposed activities contained in draft reports or documents. The public comment period is a limited time period during which comments will be accepted. (#ATSDR)

public health action: A list of steps to protect public health (#ATSDR)

public health advisory: A statement made by ATSDR to EPA or a state regulatory agency that a release of hazardous substances poses an immediate threat to human health. The advisory includes recommended measures to reduce exposure and reduce the threat to human health. (#ATSDR)

Public Health Assessment (PHA): An ATSDR document that examines hazardous substances, health outcomes, and community concerns at a hazardous waste site to determine whether people could be harmed from coming into contact with those substances. The PHA also lists actions that need to be taken to protect public health [compare with health consultation. (#ATSDR)

public health hazard: A category used in ATSDR 's public health assessments for sites that pose a public health hazard because of long-term exposures (greater than 1 year) to sufficiently high levels of hazardous substances or radionuclides that could result in harmful health effects. (#ATSDR)

(public health hazard categories*: Public health hazard categories are statements about whether people could be harmed by conditions present at the site in the past, present, or future. One or more hazard categories might be appropriate for each site. The five public health hazard categories are no public health hazard, no apparent public health hazard, indeterminate public health hazard, public health hazard, and urgent public health hazard. (#ATSDR)

public health statement: The first chapter of an ATSDR toxicological profile. The public health statement is a summary written in words that are easy to understand. The public health statement explains how people might be exposed to a specific substance and describes the known health effects of that substance. (#ATSDR)

public health surveillance: The ongoing, systematic collection, analysis, and interpretation of health data. This activity also involves timely dissemination of the data and use for public health programs (#ATSDR)

public meeting: A public forum with community members for communication about a site (#ATSDR)

pulmonary: Pertaining to the lungs (#IUPAC)

purgative: See SN cathartic, laxative (#IUPAC)

pyrexia: Condition in which the temperature of a human being or mammal is above normal (#IUPAC)

pyrogen: Any substance that produces fever (#IUPAC)


quality assurance: All those planned and systematic actions necessary to provide adequate confidence that a product or service will satisfy given requirements for quality
ISO 8402, 1986
RT good laboratory practice, quality control (#IUPAC)

quality control:
1. Operational techniques and activities that are used to fulfill requirements for quality
ISO 8402, 1986
2. In toxicology, procedures incorporated in experimental protocols to reduce the possibility of error, especially human error: this is a requirement of good laboratory practice
RT good laboratory practice, quality assurance.

quantal effect: Condition that can be expressed only as "occurring" or "not occurring," such as death or occurrence of a tumor
AN graded effect
RT stochastic effect
SN all-or-none effect

quantitative structure-activity relationship (QSAR): Quantitative association between the physicochemical properties of a substance and/or the properties of its molecular substructures and its biological properties including its toxicity
RT surrogate (#IUPAC)


radiation: Transmission of energy through space or any medium. Also known as radiant energy. (#CEHN)

radiation standards: Regulations that set maximum exposure limits for protection of the public from radioactive materials.(1) (#CEHN)

radioisotope: An unstable or radioactive isotope (form) of an element that can change into another element by giving off radiation (#ATSDR)

radionuclide: Any radioactive isotope (form) of any element (#ATSDR)

radon daughters/radon progeny: Short-lived radioactive decay products of radon that decay into longer-lived lead isotopes. The daughter isotopes can attach themselves to airborne dust and other particles and, if inhaled, damage the lining of the lung. Also known as radon decay products.(1) (#CEHN)

râles: See SN crepitations (#IUPAC)

random sample: Subset of a population that is arrived at by selecting units such that each possible unit has a fixed and determinate probability of selection
After Last, 1988
AN biased sample
BT sample (#IUPAC)

rate: Measure of the frequency of a phenomenon: an expression of the frequency with which an event occurs in a defined population during a specified time interval
Last, 1988 (#IUPAC)

rate difference (RD): Absolute difference between two rates, for example, the difference in incidence rate between a population group exposed to a causal factor and a population group not exposed to the factor: in comparisons of exposed and unexposed groups, the term "excess rate" may be used as a synonym for rate difference
Last, 1988 (#IUPAC)

rate ratio (RR): In epidemiology, the value obtained by dividing the rate in an exposed population by the rate in an unexposed population
After Last, 1988 (#IUPAC)

ratticide: Substance intended to kill rats
RT rodenticide (#IUPAC)

RCRA: see Resource Conservation and Recovery Act (1976, 1984) (#ATSDR)

readily biodegradable: Arbitrary classification of substances that have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that such compounds will be rapidly and completely biodegraded in a wide variety of aerobic environments (#IUPAC)

reasonable maximum exposure (RME): Highest exposure that is reasonably expected to occur: typically the 95% upper confidence limit of the toxicant distribution is used: if only a few data points (6-10) are available, the maximum detected concentration is used.
USEPA, 1989 (#IUPAC)

recalcitrance: Ability of a substance to remain in a particular environment in an unchanged form.
Nagel et al. (eds), 1991
RT persistence (#IUPAC)

receptor: High affinity binding site for a particular toxicant
BT target, target organ (#IUPAC)

receptor population: People who could come into contact with hazardous substances see exposure pathway. (#ATSDR)

1. Process leading to partial or complete restoration of a cell, tissue, organ or organism following its damage from exposure to a harmful substance or agent
2. Term used in analytical and preparative chemistry to denote the fraction of the total quantity of a substance recoverable following a chemical procedure
RT recovery factor
recovery factor: Fraction or percentage of the total quantity of a substance extracted under specified conditions
Gold, Loening, McNaught and Sehmi, 1987 (#IUPAC)

recycling (of waste): Process or method allowing for the recovery of some value from a waste, either as re-usable material or as energy (#IUPAC)

reference concentration: Term used for an estimate of air exposure concentration to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime
USEPA, 1989
RT acceptable daily intake
BT dose (#IUPAC)

reference distribution: Statistical distribution of reference values
Solberg, 1987 (#IUPAC)

reference dose: Term used for an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime
Barnes and Dourson, 1988
RT acceptable daily intake
BT dose (#IUPAC)

reference dose (RfD): An EPA estimate, with uncertainty or safety factors built in, of the daily lifetime dose of a substance that is unlikely to cause harm in humans (#ATSDR)

reference group: See SN reference sample group (#IUPAC)

reference individual: Person selected with the use of defined criteria for comparative purposes in a clinical study
Solberg, 1987 (#IUPAC)

reference interval: Area between and including two reference limits, for example the percentiles 2.5 and 97.5
Solberg, 1987 (#IUPAC)

reference limit: Boundary value defined so that a stated fraction of the reference values is less than or exceeds that boundary value with a stated probability
Solberg, 1987 (#IUPAC)

reference material: Substance for which one or more properties are sufficiently well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to other substances
SN calibration material, standard material
Solberg, 1987 (#IUPAC)

reference population: Group of all reference individuals used to establish criteria against which a population that is being studied can be compared
Solberg, 1987 (#IUPAC)

reference sample group: Selected reference individuals, statistically adequate numerically to represent the reference population
Solberg, 1987 (#IUPAC)

reference value: According to IFCC, measured value of a property in a reference individual or sample from a reference individual
Solberg, 1987 (#IUPAC)

registry: A systematic collection of information on persons exposed to a specific substance or having specific diseases see exposure registry and disease registry (#ATSDR)

registration: Formal listing with EPA of a new pesticide before it can be sold or distributed: under the Federal Insecticide, Fungicide, and Rodenticide Act. EPA is responsible for registration (pre-market licensing) of pesticides on the basis of data demonstrating no unreasonable adverse effects on human health or the environment when applied according to approved label directions.(1) (#IUPAC)

Registry of Inactive Hazardous Waste Disposal Sites: The New York State Department of Environmental Conservation (DEC) maintains a list of inactive hazardous waste disposal sites in New York State. When DEC finds that a site may contain hazardous waste, the site is listed in the registry and a preliminary site assessment is planned. The status of the site is updated in the registry as investigations and remediation occur. ((#IUPAC)

regulatory dose: Term used by the EPA to describe the expected dose resulting from human exposure to a substance at the level at which it is regulated in the environment
Barnes and Dourson, 1988 (#IUPAC)

relative odds: See SN odds ratio

relative risk:
1. Ratio of the risk of disease or death among the exposed to that among the unexposed
SN risk ratio
2. Ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed; the cumulative incidence ratio
Last, 1988

release: Any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment of a hazardous or toxic chemical or extremely hazardous substance.(1) (#CEHN)

remedial investigation: The CERCLA process of determining the type and extent of hazardous material contamination at a site (#ATSDR)

remedial response: Long-term action that stops or substantially reduces a release or threat of a release of hazardous substances that is serious but not an immediate threat to public health.(1) (#CEHN)

remediation: Correction or improvement of a problem, such as work that is done to clean up or stop the release of chemicals from a contaminated site. After investigation of a site, remedial work may include removing soil and/or drums, capping the site or collecting and treating the contaminated fluids. (#Glossary)

renal: Pertaining to the kidneys (#IUPAC)

repellent: Substance used mainly to repel blood sucking insects in order to protect man and animals: also used to repel mammals, birds, rodents, mites, plant pests, etc. (#IUPAC)

replicate sampling: Act of taking multiple samples concurrently under comparable conditions; may be accomplished by taking samples adjacent in time or space
PAC, 1990 (#IUPAC)

1. Duplicated or repeated performance of an experiment under similar (controlled) conditions to reduce to a minimum the error, and to estimate the variations and thus obtain a more precise result: each determination, including the first is called a replicate
2. Process whereby the genetic material is duplicated.
reproducibility: Closeness of agreement between test results obtained under reproducibility conditions (see below)
ISO 5725, 1986
RT reproducibility conditions (#IUPAC)

reproducibility conditions: Situation where test results are obtained with the same method on identical test material in different laboratories with different operators using different equipment
ISO 5725, 1986 (#IUPAC)

reproductive toxicant: Substance or preparation that produces non-heritable harmful effects on the progeny and/or an impairment of male and female reproductive function or capacity
USEPA, 1986
RT teratogen (#IUPAC)

reproductive toxicology: Study of the adverse effects of substances on the embryo, fetus, neonate and prepubertal mammal and the adult reproductive and neuro-endocrine systems
RT embryo, fetus, neonate (#IUPAC)

reserve capacity: Physiological or biochemical capacity that may be available to maintain homeostasis when the body or an organism is exposed to an environmental change (#IUPAC)

resistance (in toxicology): Ability to withstand the effect of various factors including potentially toxic substances (#IUPAC)

resorptive effect: Action of a substance after its resorption from the gut into the blood
IRPTC, 1982 (International)
Resource Conservation and Recovery Act (1976, 1984) (RCRA): This Act regulates management and disposal of hazardous wastes currently generated, treated, stored, disposed of, or distributed (#ATSDR)

1. Proportion of an exposed population with a defined effect or the proportion of a group of individuals that demonstrate a defined effect in a given time at a given dose rate
RT dose-response relationship
2. Reaction of an organism or part of an organism (such as a muscle) to a stimulus

1. Holding back within the body or within an organ, tissue or cell of matter that is normally eliminated
AN elimination
2. Holding in memory of what has been learned for later use as recall, recognition or relearning
3. Amount of a substance that is left from the total absorbed after a certain time following exposure: if the retention follows a course in relation to time that is a first order process, it may be described in terms of biological half-life (half-time)
RT half-life

retrospective study: Research design used to test aetiological hypotheses in which inferences about exposure to the putative causal factor(s) are derived from data relating to characteristics of the persons or organisms under study or to events or experiences in their past: the essential feature is that some of the persons under study have the disease or other outcome condition of interest, and their characteristics and past experiences are compared with those of other, unaffected persons. Persons who differ in the severity of the disease may also be compared
RT case control study
Last, 1988 (#IUPAC)

returned effect of poisons: Enhancement of the dose-effect relationship for a poison following repeated exposure to decreasing doses (#IUPAC)

reverse transcription: Process by which an RNA molecule is used as a template to make a single-stranded DNA copy (International)

reversible alteration: Change from normal structure or function, induced by a substance or other agent(s), that returns to normal status or within normal limits after cessation of exposure (#IUPAC)

RFA: RCRA Facility Assessment. An assessment required by RCRA to identify potential and actual releases of hazardous chemicals (#ATSDR)

RfD: see reference dose (#ATSDR)

rhabdomyolysis: Acute, fulminating, potentially lethal disease of skeletal muscle that causes disintegration of striated muscle fibres as evidenced by myoglobin in the blood and urine (#IUPAC)

rhinitis: Inflammation of the nasal mucosa (#IUPAC)

rhonchus: Harsh crepitation in the throat, often resembling snoring
BT crepitations (#IUPAC)

ribonucleic acid: Linear, usually single stranded, polymer of ribonucleotides, each containing the sugar ribose in association with a phosphate group and one of 4 nitrogenous bases: adenine, guanine, cytosine, or uracil: it encodes the information for the sequence of amino-acids in proteins synthesized using it as a template
RT deoxyribonucleic acid (#IUPAC)

Right-to-Know: See Community Right-to-Know Reporting Requirements. (#CEHN)

1. Possibility that a harmful event (death, injury or loss) arising from exposure to a chemical or physical agent may occur under specific conditions
2. Expected frequency of occurrence of a harmful event (death, injury or loss) arising from exposure to a chemical or physical agent under specific conditions
NT excess lifetime risk, extra risk
RT hazard
risk acceptance: Decision that the risk associated with a given chemical exposure or an event leading to such exposure is low enough to be tolerated in order to gain associated benefits
RT acceptable risk (#IUPAC)

risk assessment: Identification and quantification of the risk resulting from a specific use or occurrence of a chemical or physical agent, taking into account possible harmful effects on individual people or society of using the chemical or physical agent in the amount and manner proposed and all the possible routes of exposure. Quantification ideally requires the establishment of dose-effect and dose-response relationships in likely target individuals and populations
RT exposure assessment, hazard identification, risk characterization, risk estimation, risk evaluation, risk identification, risk management, risk perception (#IUPAC)

risk assessment management process: Global term for the whole process from hazard identification to risk management
WHO, 1988
RT hazard identification, risk management (#IUPAC)

risk associated with a life time exposure: Probability of the occurrence of a specified undesirable event following exposure of an individual person from a given population to a specified substance at a defined level for the expected lifetime of the average member of that population (#IUPAC)

risk aversion: Term used to describe the tendency of an individual person to avoid risk (#IUPAC)

risk characterization: Outcome of hazard identification and risk estimation applied to a specific use of a substance or occurrence of an environmental health hazard: the assessment requires quantitative data on the exposure of organisms or people at risk in the specific situation. The end product is a quantitative statement about the proportion of organisms or people affected in a target population
After WHO, 1979
RT hazard identification, risk estimation (#IUPAC)

risk communication: Interpretation and communication of risk assessments in terms that are comprehensible to the general public or to others without specialist knowledge (#IUPAC)

risk de minimis: Risk that is negligible and too small to be of societal concern (usually assumed to be a probability below 10-5 or 10-6); can also mean 'virtually safe'. In the USA, this is a legal term used to mean "negligible risk to the individual"
SN negligible risk (#IUPAC)

risk estimation: Assessment, with or without mathematical modelling, of the probability and nature of effects of exposure to a substance based on quantification of dose-effect and dose-response relationships for that substance and the population(s) and environmental components likely to be exposed and on assessment of the levels of potential exposure of people, organisms and environment at risk
RT risk evaluation
RT exposure assessment, hazard identification (#IUPAC)

risk evaluation: Establishment of a qualitative or quantitative relationship between risks and benefits, involving the complex process of determining the significance of the identified hazards and estimated risks to those organisms or people concerned with or affected by them
RT exposure evaluation, hazard identification, risk assessment, risk characterization, risk estimation, risk identification, risk perception (#IUPAC)

risk identification: Recognition of a potential hazard and definition of the factors required to assess the probability of exposure of organisms or people to that hazard and of harm resulting from such exposure (#IUPAC)

risk indicator: See SN risk marker (#IUPAC)

risk management: Decision-making process involving considerations of political, social, economic, and engineering factors with relevant risk assessments relating to a potential hazard so as to develop, analyse, and compare regulatory options and to select the optimal regulatory response for safety from that hazard. Essentially risk management is the combination of three steps: risk evaluation; emission and exposure control; risk monitoring
RT emission and exposure control, risk evaluation, risk monitoring (#IUPAC)

risk marker: Attribute that is associated with an increased probability of occurrence of a disease or other specified outcome and that can be used as an indicator of this increased risk: not necessarily a causal or pathogenic factor
SN risk indicator
Last, 1988 (#IUPAC)

risk monitoring: Process of following up the decisions and actions within risk management in order to check whether the aims of reduced exposure and risk are achieved
BT monitoring
RT risk management
WHO, 1988 (#IUPAC)

risk perception: Subjective perception of the gravity or importance of the risk based on a person's knowledge of different risks and the moral, economic, and political judgement of their implications
RT risk evaluation
WHO, 1988 (#IUPAC)

risk phrases: Word groups identifying potential health or environmental hazards required under CPL Directives (European Community); may be incorporated into Safety Data Sheets
RT material safety data sheet, safety data sheet (#IUPAC)

risk ratio: Value obtained by dividing the probability of occurrence of a specific effect in one group by the probability of occurrence of the same effect in another group, or the value obtained by dividing the probability of occurrence of one potentially hazardous event by the probability of occurrence of another. Calculation of such ratios is used in choosing between options in risk management
RT risk management (International)
risk reduction: Actions that can decrease the likelihood that individuals, groups, or communities will experience disease or other health conditions (ATSDR)
risk-specific dose: Amount of exposure corresponding to a specified level of risk
USEPA, 1989 (#IUPAC)

rodenticide: Substance intended to kill rodents (#IUPAC)

route of exposure: Means by which a toxic agent gains access to an organism by administration through the gastrointestinal tract (ingestion), lungs (inhalation), skin (topical), or by other routes such as intravenous, subcutaneous, intramuscular or intraperitoneal routes (#IUPAC)


safe: Strictly, free from harm or risk. Exposure to a chemical usually has some risk associated with it, although the risk may be very small. However, many people use the word safe to mean something that has a very low risk or one that is acceptable to them. (#Glossary)

safety: Reciprocal of risk: practical certainty that injury will not result from a hazard under defined conditions.
1. Safety of a drug or other substance in the context of human health: the extent to which a substance may be used in the amount necessary for the intended purpose with a minimum risk of adverse health effects.
2. Safety (toxicological): The high probability that injury will not result from exposure to a substance under defined conditions of quantity and manner of use, ideally controlled to minimize exposure. RT practical certainty, risk.
safety data sheet: Single page giving toxicological and other safety advice, usually associated with a particular preparation, substance or process (#IUPAC)

safety factor: See SN uncertainty factor (#IUPAC)

saluretic: See SN natriuretic (#IUPAC)

1. In statistics, a group of individuals often taken at random from a population for research purposes
2. One or more items taken from a population or a process and intended to provide information on the population or process.
3. Portion of material selected from a larger quantity in some manner chosen so that the portion is representative of the whole.
PAC, 1990
RT biased sample, random sample, stratified sample, systematic sample.
sample size: The number of units chosen from a population or an environment (#ATSDR)

sampling: Procedure used to obtain or constitute a sample.
RT sample (#IUPAC)

sampling error: Part of the total estimation error of a parameter (or alue of a property, such as concentration) caused by the random nature of the sample.
ISO, 1977
RT sample, sampling (#IUPAC)

SARA: (see Superfund Amendments and Reauthorization Act]) (#ATSDR)

sarcoma: Malignant tumour arising in a connective tissue and composed primarily of anaplastic cells resembling supportive tissue (#IUPAC)

saturnism: Intoxication caused by lead.
SN plumbism (#IUPAC)

scotoma: Area of depressed vision within the visual field, surrounded by an area of less depressed or normal vision (#IUPAC)

sclerosis: Hardening of an organ or tissue, especially that due to excessive growth of fibrous tissue (#IUPAC)

1. Carrying out of a test or tests, examination(s) or procedure(s) in order to expose undetected abnormalities, unrecognized (incipient) diseases, or defects: examples are mass X-rays and cervical smears.
2. Pharmacological or toxicological screening consists of a specified set of procedures to which a series of compounds is subjected to characterize pharmacological and toxicological properties and to establish dose-effect and dose-response relationships. (#IUPAC)

screening level: Decision limit or cut-off point at which a screening test is regarded as positive.
Last, 1988 (#IUPAC)

secondary metabolite: Product of biochemical processes other than the normal metabolic pathways, mostly produced in micro-organisms or plants after the phase of active growth and under conditions of nutrient deficiency.
After Nagel et al. (eds), 1991 (#IUPAC)

secondary pollutant: See BT pollutant (#IUPAC)

secondhand smoke: See SN sidestream smoke (#IUPAC)

1. Process by which a substance such as a hormone or enzyme produced in a cell is passed through a plasma membrane to the outside, for example the intestinal lumen or the blood (internal secretion)
2. Solid, liquid or gaseous material passed from the inside of a cell through a plasma membrane to the outside as a result of cell activity.
sedative: Substance that exerts a soothing or tranquillising effect.
RT anaesthetic, narcotic (#IUPAC)

self-cleaning of water (in a reservoir): Water purification by natural biological and physico-chemical processes (#IUPAC)

self-purification of the atmosphere: Purification of the atmosphere from contaminants by natural biological and physico-chemical processes.
RT contaminant (#IUPAC)

semichronic: See SN subchronic (#IUPAC)

sensibilization: See SN sensitization (#IUPAC)

sensitivity (in analytical chemistry): Extent to which a small change in concentration of an analyte can cause a large change in the related measurement.
Gold, Loening, McNaught and Sehmi, 1987 (#IUPAC)

sensitivity (of a screening test): Extent (usually expressed as a percentage) to which a method gives results that are free from false negatives; the fewer the false negatives, the greater the sensitivity (#IUPAC). Quantitatively, sensitivity is the proportion of truly diseased persons in the screened population who are identified as diseased by the screening test.
Galen and Gambino, 1975
RT specificity (of a screening test) (#IUPAC)

sensitization: Immune process whereby individuals become hypersensitive to substances, pollen, dandruff, or other agents that make them develop a potentially harmful allergy when they are subsequently exposed to the sensitizing material (allergen).
RT allergy, hypersensitivity (#IUPAC)

sensory effect level:
1. Intensity, where the detection threshold level is defined as the lower limit of the perceived intensity range (by convention the lowest concentration that can be detected in 50% of the cases in which it is present).
2. Quality, where the recognition threshold level is defined as the lowest concentration at which the sensory effect can be recognized correctly in 50% of the cases.
3. Acceptability and annoyance, where the nuisance threshold level is defined as the concentration at which not more than a small proportion of the population, less than 5%, experiences annoyance for a small part of the time, less than 2% since annoyance will be influenced by a number of factors, a nuisance threshold level cannot be set on the basis of concentration alone.
RT nuisance threshold.
WHO, 1987 (#IUPAC)

1. Watery proteinaceous portion of the blood that remains after clotting.
SN blood serum.
2. Clear watery fluid especially that moistening the surface of serous membranes or that exuded through inflammation of any of these membranes.
short term effect: See SN acute effect (#IUPAC)

short term exposure limit (STEL): As used by US NIOSH, unless noted otherwise, the 15 minute time weighted average exposure that should not be exceeded at any time during a work day (#IUPAC)

side-effect: Action of a drug other than that desired for beneficial pharmacological effect (#IUPAC)

1.Pneumoconiosis resulting from the inhalation of iron dust.
BT pneumoconiosis.
2. Excess of iron in the urine, blood or tissues, characterized by haemosiderin granules in urine and iron deposits in tissues.

sidestream smoke: Cloud of small particles and gases that is given off from the end of a burning tobacco product (cigarette, pipe, cigar) between puffs and is not directly inhaled by the smoker; the smoke that gives rise to passive inhalation on the part of bystanders.
SN secondhand smoke.
RT mainstream smoke (#IUPAC)

sign: Objective evidence of a disease, deformity or an effect induced by an agent, perceptible to an examining physician (#IUPAC)

silicosis: Pneumoconiosis resulting from inhalation of silica dust.
BT pneumoconiosis (#IUPAC)

simulation test: Procedure designed to predict the rate of biodegradation of a compound under relevant environmental conditions (#IUPAC)

sink: In environmental chemistry, an area or part of the environment in which, or a process by which, one or more pollutants is removed from the medium in which it is dispersed; for example - moist ground acts as a sink for sulfur dioxide in the air. (#IUPAC)

sister chromatid exchange (SCE): Reciprocal exchange of chromatin between two replicated chromosomes that remain attached to each other until anaphase of mitosis; used as a measure of mutagenicity of substances that produce this effect.
RT mitosis (#IUPAC)

site inspection: A Department of Health visit to a site to evaluate the likelihood of human exposure to toxic chemicals, and to do an exposure assessment. See "Exposure assessment." (#Glossary)

siting: The process of choosing a location for a facility. (#CEHN)

skeletal fluorosis: Osteosclerosis due to fluoride (#IUPAC)

slimicide: Substance intended to kill slime-producing organisms (used on paper stock, water cooling systems, paving stones etc.) (#IUPAC)

slope factor: Value, in inverse concentration or dose units, derived from the slope of a dose-response curve; in practice, limited to carcinogenic effects with the curve assumed to be linear at low concentrations or doses. The product of the slope factor and the exposure is taken to reflect the probability of producing the related effect.
RT concentration-effect curve, concentration-response curve, dose, dose-effect curve, dose-response curve. (#IUPAC)

smog: Air pollution associated with oxidants. (See: photochemical smog.)(1) (#CEHN)

societal risk: Total probability of harm to a human population including also the probability of adverse health effects to descendants and the probability of disruption resulting from loss of services such as industrial plant or loss of material goods and electricity. (#IUPAC)

solubility: The largest amount of a substance that can be dissolved in a given amount of a liquid, usually water. For a highly water-soluble compound, such as table salt, a lot can dissolve in water. Motor oil is only slightly soluble in water (#Glossary)

[ ]: A liquid capable of dissolving or dispersing another substance (for example, acetone or mineral spirits). (#ATSDR)

solvent abuse: Deliberate inhalation (or drinking) of volatile Solvents - Chemical Profiles and External Links, in order to become intoxicated.
SN "solvent sniffing".
NT "glue sniffing". (#IUPAC)

"solvent sniffing": See SN solvent abuse.
NT "glue sniffing". (#IUPAC)

1. Pertaining to the body as opposed to the mind.
2. Pertaining to nonreproductive cells or tissues.
3. Pertaining to the framework of the body as opposed to the viscera.

soporific: Substance producing sleep.
RT anaesthetic, narcotic, sedative (#IUPAC)

sorption: Noncommittal term used instead of adsorption or absorption when it is difficult to discriminate experimentally between these two processes.
Gold, Loening, McNaught and Sehmi, 1987 (#IUPAC)

source of contamination: The place where a hazardous substance comes from, such as a landfill, waste pond, incinerator, storage tank, or drum. A source of contamination is the first part of an exposure pathway (#ATSDR)

special populations: People who might be more sensitive or susceptible to exposure to hazardous substances because of factors such as age, occupation, sex, or behaviors (for example, cigarette smoking). Children, pregnant women, and older people are often considered special populations (#ATSDR)

speciation: Determination of the exact chemical form or compound in which an element occurs in a sample, for instance - determination of whether arsenic occurs in the form of trivalent or pentavalent ions or as part of an organic molecule, and the quantitative distribution of the different chemical forms that may coexist (#IUPAC)

1. In biological systematics, group of organisms of common ancestry that are able to reproduce only among themselves and that are usually geographically distinct.
2. See NT chemical species.
species differences in sensitivity: Quantitative or qualitative differences of response to the action(s) of a potentially toxic substance on various species of living organisms.
RT species-specific sensitivity (#IUPAC)

species-specific sensitivity: Quantitative and qualitative features of response to the action(s) of a potentially toxic substance that are characteristic for particular species of living organism.
RT species differences in sensitivity (#IUPAC)

specific death rate: Death rate computed for a subpopulation of individual organisms or people having a specified characteristic or attribute, and named accordingly (for example, age-specific death rate, the number of deaths of persons of a specified age during a given period of time, divided by the total number of persons of that age in the population during that time).
IPCS, 1978 (#IUPAC)

specificity (of a screening test): Proportion of truly non-diseased persons who are identified by the screening test (#IUPAC)

specific pathogen free (SPF): Describing an animal removed from its mother under sterile conditions just prior to term and subsequently reared and kept under sterile conditions.
RT germ-free animal (#IUPAC)

specimen: Specifically selected portion of any substance, material, organism (specifically tissue, blood, urine or feces) or environmental medium assumed to be representative of the parent substance etc. at the time it is taken for the purpose of diagnosis, identification, study or demonstration.
PAC, 1990 (#IUPAC)

spreader: Agent used in some pesticide formulations to extend the even disposition of the active ingredient (#IUPAC)

stability half-life (half-time): Time required for the amount of a substance in a formulation to decrease, for any reason, by one-half (50%).
Brown, 1988 (#IUPAC)

stakeholder: A person, group, or community who has an interest in activities at a hazardous waste site (#ATSDR)

1. That which is established as a measure or model to which others of a similar nature should conform.
2. Technical specification, usually in the form of a document available to the public, drawn up with the consensus or general approval of all interests affected by it, based on the consolidated results of science, technology and experience, aimed at the promotion of optimum community benefits and approved by a body recognized on the national, regional or international level.
SN technical directive.
3. Reference substance.
SN standard material.

1. Making any substance, drug or other preparation conform to type or precisely defined characteristics.
2. Establishment of precisely defined characteristics, or precisely defined methods, for future reference.
3. Definition of precise procedures for administering, scoring and evaluating the results of a new method that is under development.

standard material (in analytical chemistry):
1. Reference material (or calibration material) for which, for specified element concentrations, values are recommended by some official body.
Gold, Loening, McNaught and Sehmi, 1987
2. Substance sufficiently well defined to be used for calibration and quality control of measurement techniques.
PS reference material.
standard(ized) mortality (morbidity) ratio (SMR): Ratio of the number of events observed in the study group or population to the number of deaths expected if the study population had the same specific rates as the standard population, multiplied by 100.
Last, 1988 (#IUPAC)

stannosis: Pneumoconiosis resulting from inhalation of tin dust (International)
statistics: A branch of mathematics that deals with collecting, reviewing, summarizing, and interpreting data or information. Statistics are used to determine whether differences between study groups are meaningful. (#ATSDR)

stochastic: Of, pertaining to or arising from chance and hence involving probability and obeying the laws of probability (#IUPAC)

stochastic effect: Consequence for which the probability of occurrence depends on the absorbed dose: hereditary effects and cancer induced by radiation are considered to be stochastic effects. The term "stochastic" indicates that the occurrence of effects so named, would be random. This means that, even for an individual, there is no threshold of dose below which the effect will not appear, and the chance of experiencing the effect increases with increasing dose.
WHO, 1989a
RT all-or-none effect, quantal effect (#IUPAC)

stratification (in epidemiology): Process of or result of separating a sample into several subsamples according to specified criteria such as age groups, socio-economic status, etc.
Last, 1988 (#IUPAC)

stratified sample: Subset of a population selected according to some important characteristic.
RT stratification (#IUPAC)

structure-activity relationship (SAR): Association between the physicochemical properties of a substance and/or the properties of its molecular substructures and its biological properties including its toxicity.
PS quantitative structure-activity relation (QSAR) (#IUPAC)

subacute: Term used to describe a form of repeated exposure or administration usually occurring over about 21 days, not long enough to be called "long-term" or "chronic"
PS subchronic.
RT subacute effect, subchronic effect, subchronic toxicity, subchronic toxicity test (#IUPAC)

subacute (sometimes called subchronic) effect: Biological change resulting from multiple or continuous exposures usually occurring over about 21 days. Sometimes the term is used synonymously with subchronic effect and care should be taken to check the usage any particular case.
PS subchronic effect.
RT subchronic toxicity, subchronic toxicity test (#IUPAC)

subchronic: Related to repeated dose exposure over a short period, usually about 10% of the life span; an imprecise term used to describe exposures of intermediate duration.
PS subacute.
RT subacute effect, subchronic effect, subchronic toxicity,[ subchronic toxicity test|http://sis.nlm.nih.gov/enviro/glossarys.html#subchronicsometimescalledsubacutetoxicitytest].
SN semichronic (#IUPAC)

subchronic (sometimes called subacute) effect: Biological change resulting from an environmental alteration lasting about 10% of the lifetime of the test organism . In practice with experimental animals, such an effect is usually identified as resulting from multiple or continuous exposures occurring over 3 months (90 days). Sometimes a subchronic effect is distinguished from a subacute effect on the basis of its lasting for a much longer time.
PS subacute effect.
RT subchronic toxicity, subchronic toxicity test (#IUPAC)

subchronic toxicity:
1. Adverse effects resulting from repeated dosage or exposure to a substance over a short period, usually about 10% of the life span.
2. The capacity to produce adverse effects following subchronic exposure.
RT subacute, subchronic, subchronic effect, subchronic toxicity test.
subchronic (sometimes called subacute) toxicity test: Animal experiment serving to study the effects produced by the test material when administered in repeated doses (or continually in food, drinking-water, air) over a period of up to about 90 days.
WHO, 1979
SN semichronic toxicity test (#IUPAC)

subclinical effect: Biological change following exposure to an agent known to cause disease either before symptoms of the disease occur or when they are absent (#IUPAC)

subjective environment: Surrounding conditions as perceived by persons living in these conditions.
SN perceived environment
After WHO, 1979 (#IUPAC)

substance: A chemical (#ATSDR)

substance-specific applied research: A program of research designed to fill important data needs for specific hazardous substances identified in ATSDR's toxicological profiles. Filling these data needs would allow more accurate assessment of human risks from specific substances contaminating the environment. This research might include human studies or laboratory experiments to determine health effects resulting from exposure to a given hazardous substance. (#ATSDR)

subthreshold dose: See SN non-effective dose (#IUPAC)

sudorific: Substance that causes sweating (#IUPAC)

sufficient evidence: According to the USEPA's Guidelines for Carcinogen Risk Assessment, sufficient evidence is a collection of facts and scientific references that is definite enough to establish that an adverse effect is caused by the agent in question.
RT carcinogenicity, classification according to IARC, limited evidence (#IUPAC)

suggested no adverse response level (SNARL): Maximum dose or concentration that on current understanding is likely to be tolerated by an exposed organism without producing any harm (#IUPAC)

summary sheet: Two-to-four page summary of a risk assessment
IRIS, 1986 (#IUPAC)

summation (in neurophysiology): Process of addition of separate postsynaptic responses caused by stimuli that are adjacent in time and space. Excitation of a synapse evokes a graded potential change in the postsynaptic membrane that may be below the threshold required to trigger an impulse. If two or more such potentials are caused either nearly simultaneously, at different synapses on the same neurone (spatial summation), or in rapid succession at the same synapse (temporal summation), the summed response may be sufficient to trigger a postsynaptic impulse. Summation may occur between excitatory potentials, inhibitory potentials, or between an excitatory and an inhibitory potential (#IUPAC)

superfund: Federal authority, established by the US Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in 1980, to respond directly to releases or threatened releases (such as from dumps) of hazardous substances that may endanger health or welfare
IRIS, 1986 (#IUPAC)

Superfund Amendments and Reauthorization Act (SARA):
In 1986, SARA amended the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) and expanded the health-related responsibilities of ATSDR. CERCLA and SARA direct ATSDR to look into the health effects from substance exposures at hazardous waste sites and to perform activities including health education, health studies, surveillance, health consultations, and toxicological profiles. (#ATSDR)

super-threshold dose: See PS toxic dose (#IUPAC)

surface layer: Region of space comprising and adjoining the phase boundary between a solid and liquid phase, between a solid and gas phase, or between a liquid and gas phase within which properties of matter are significantly different from the values in the adjoining bulk phases
PS interfacial layer (#IUPAC)

surface water: Water on the surface of the earth, such as in lakes, rivers, streams, ponds, and springs (compare with groundwater) (ATSDR)
surrogate: Relatively well studied toxicant whose properties are assumed to apply to an entire chemically and toxicologically related class; for example, benzo(a)pyrene data may be used as toxicologically equivalent to that for all carcinogenic polynuclear aromatic hydrocarbons
RT quantitative structure-activity relationship (#IUPAC)

surveillance: Ongoing scrutiny, generally using methods distinguished by their practicability and uniformity, and frequently by their rapidity, rather than by complete accuracy. Its main purpose is to detect changes in trend or distribution in order to initiate investigative or control measures
Last, 1988 (International)
survey: A systematic collection of information or data. A survey can be conducted to collect information from a group of people or from the environment. Surveys of a group of people can be conducted by telephone, by mail, or in person. Some surveys are done by interviewing a group of people (see prevalence survey). (#ATSDR)

susceptibility: Condition of lacking the power to resist a particular disease or infection; thus in susceptible people "normal expected" results occur but with a lower exposure (or dose) than in the rest of the population (#IUPAC)

1. adj., Blocking transmission of impulses from the adrenergic (sympathetic) postganglionic fibres to effector organs or tissues.
2. n., Agent that blocks transmission of impulses from the adrenergic (sympathetic) postganglionic fibres to effector organs or tissues
SN antiadrenergic

1. adj., Producing effects resembling those of impulses transmitted by the postganglionic fibres of the sympathetic nervous system.
2. n., Agent that produces effects resembling those of impulses transmitted by the postganglionic fibres of the sympathetic nervous system.
SN adrenergic

symptom: Any subjective evidence of a disease or an effect induced by a substance as perceived by the affected subject (#IUPAC)

symptomatology: General description of all of the signs and symptoms of exposure to a toxicant: signs are the overt (observable) responses associated with exposure (such as convulsions, death, etc.) whereas symptoms
are covert (subjective) responses (such as nausea, headache, etc.).
Brown, 1988|http://sis.nlm.nih.gov/enviro/annex3.html#BROWNVK] (#IUPAC)

synapse: Functional junction between two neurones, where a nerve impulse is transmitted from one neurone to another (#IUPAC)

synaptic transmission: See RT synapse (#IUPAC)

syndrome: Set of signs and symptoms occurring together and often characterizing a particular disease-like state (#IUPAC)

synergism: Pharmacological or toxicological interaction in which the combined biological effect of two or more substances is greater than expected on the basis of the simple summation of the toxicity of each of the individual substances (#IUPAC)

synergistic effect: Biological effect following exposure simultaneously to two or more substances that is greater than the simple sum of the effects that occur following exposure to the substances separately
RT additive effect, antagonism, potentiation (#IUPAC)

systematic sample: Subset selected according to some simple rule such as specified date or alphabetic classification
RT biased sample, stratified sample (#IUPAC)

systemic: Relating to the body as a whole (#IUPAC)

systemic effect: Consequence that is of either a generalized nature or that occurs at a site distant from the point of entry of a substance: a systemic effect requires absorption and distribution of the substance in the body (#IUPAC)


tachy-: Prefix meaning rapid as in tachycardia and tachypnoea (#IUPAC)

tachycardia: Abnormally fast heartbeat
AN bradycardia (#IUPAC)

tachypnoea: Abnormally fast breathing
AN bradypnoea (#IUPAC)

taeniacide: Substance intended to kill tapeworms (#IUPAC)

target (biological): Any organism, organ, tissue, cell or cell constituent that is subject to the action of a pollutant or other chemical, physical, or biological agent
WHO, 1979
RT receptor (#IUPAC)

target (of environmental pollution): Human being or any organism, organ tissue, cell, resource, or any constituent of the environment, living or not, that is subject to the activity of a pollutant or other chemical or physical activity or other agent
WHO, 1979
RT receptor (#IUPAC)

target organ(s): Organ(s) in which the toxic injury manifests itself in terms of dysfunction or overt disease
WHO, 1979
RT receptor (#IUPAC)

target population (epidemiology):
1. Collection of individuals, items, measurements, etc. about which we want to make inferences: the term is sometimes used to indicate the population from which a sample is drawn and sometimes to denote any reference population about which inferences are required
2. Group of persons for whom an intervention is planned
Last, 1988 (#IUPAC)

T cell: See T lymphocyte (#IUPAC)

technical directive: See RT standard (#IUPAC)

temporary acceptable daily intake: Value for the acceptable daily intake proposed for guidance when data are sufficient to conclude that use of the substance is safe over the relatively short period of time required to generate and evaluate further safety data, but are insufficient to conclude that use of the substance is safe over a lifetime. A higher-than-normal safety factor is used when establishing a temporary ADI and an expiration date is established by which time appropriate data to resolve the safety issue should be available
RT acceptable daily intake
After de Koning, 1987 (#IUPAC)

temporary maximum residue limit: Temporary maximum residue limit is established for a specified, limited period when:
1. Only a temporary acceptable daily intake has been established for the pesticide concerned
2. Although an acceptable daily intake has been established, the residue data are inadequate for firm maximum residue recommendations
WHO, 1976
teratogen: Agent that, when administered prenatally (to the mother), induces permanent structural malformations or defects in the offspring (#IUPAC)

teratogenicity: Potential to cause or the production of structural malformations or defects in offspring
After WHO, 1987
RT developmental toxicity, embryotoxicity (#IUPAC)

testing of chemicals:
1. In toxicology, evaluation of the therapeutic and potentially toxic effects of substances by their application through relevant routes of exposure with appropriate organisms or biological systems so as to relate effects to dose following application
2. In chemistry, qualitative or quantitative analysis by the application of one or more fixed methods and comparison of the results with established standards

titanic: Pertaining to tetanus, characterized by tonic muscle spasm (#IUPAC)

therapeutic index: Ratio between toxic and therapeutic doses (the higher the ratio, the greater the safety of the therapeutic dose) (#IUPAC)

threshold: Dose or exposure concentration below which an effect is not expected (#IUPAC)

threshold limit value (TLV): Concentration in air of a substance to which it is believed that most workers can be exposed daily without adverse effect (the threshold between safe and dangerous concentrations). These values are established (and revised annually) by the American Conference of Governmental Industrial Hygienists) and are time-weighted concentrations for a 7 or 8 hour workday and a 40 hour workweek. For most substances the value may be exceeded, to a certain extent, provided there are compensatory periods of exposure below the value during the workday (or in some cases the week). For a few substances (mainly those that produce a rapid response) the limit is given as a ceiling concentration (maximum permissible concentration - designated by "C") that should never be exceeded (#IUPAC)

thrombocytopenia: Decrease in the number of blood platelets (thrombocytes) (#IUPAC)

tidal volume: Quantity of air or test gas that is inhaled and exhaled during one respiratory cycle (#IUPAC)

time-weighted average exposure (TWAE) or concentration (TWAC): Concentration in the exposure medium at each measured time interval multiplied by that time interval and divided by the total time of observation: for occupational exposure a working shift of eight hours is commonly used as the averaging time
WHO, 1979 (#IUPAC)

tinnitus: Continual noise in the ears, such as ringing, buzzing, roaring, or clicking (#IUPAC)

tissue dose: Amount of a substance or physical agent (radiation) absorbed by a tissue (#IUPAC)

T lymphocyte: Animal cell which possesses specific cell surface receptors through which it binds to foreign substances or organisms, or those which it identifies as foreign, and which initiates immune responses
RT B lymphocyte, immune response, lymphocyte (#IUPAC)

tolerable daily intake (TDI): Regulatory value equivalent to the acceptable daily intake established by the European Commission Scientific Committee on Food. Unlike the ADI, the TDI is expressed in mg/person, assuming a body weight of 60 kg. TDI is normally used for food contaminants
RT acceptable daily intake (#IUPAC)

tolerable risk: Probability of suffering disease or injury that can, for the time being, be tolerated, taking into account the associated benefits, and assuming that the risk is minimized by appropriate control procedures
PS acceptable risk (#IUPAC)

1. Adaptive state characterized by diminished effects of a particular dose of a substance: the process leading to tolerance is called "adaptation"
2. In food toxicology, dose that an individual can tolerate without showing an effect
3. Ability to experience exposure to potentially harmful amounts of a substance without showing an adverse effect
4. Ability of an organism to survive in the presence of a toxic substance: increased tolerance may be acquired by adaptation to constant exposure.
5. In immunology, state of specific immunological unresponsiveness

1. Characterised by tension, especially muscular tension.
2. Medical preparation that increases or restores normal muscular tension
topical: Pertaining to a particular area, as in a topical effect that involves only the area to which the causative substance has been applied (#IUPAC)

total diet study:
1. Study designed to establish the pattern of pesticide residue intake by a person consuming a defined diet.
WHO, 1976.
2. Study undertaken to show the range and amount of various foodstuffs in the typical diet or to estimate the total amount of a specific substance in a typical diet
After WHO, 1989a
toxic: Able to cause injury to living organisms as a result of physicochemical interaction
toxic agent: Chemical or physical (for example, radiation, heat, cold, microwaves) agents that, under certain circumstances of exposure, can cause harmful effects to living organisms (#ATSDR)

toxicant: See SN toxic substance (#IUPAC)

toxic chemical: See SN toxic substance (#IUPAC)

toxic dose: Amount of a substance which produces intoxication without lethal outcome
SN super-threshold dose (#IUPAC)

1. Capacity to cause injury to a living organism defined with reference to the quantity of substance administered or absorbed, the way in which the substance is administered (inhalation, ingestion, topical application, injection) and distributed in time (single or repeated doses), the type and severity of injury, the time needed to produce the injury, the nature of the organism(s) affected and other relevant conditions.
2. Adverse effects of a substance on a living organism defined with reference to the quantity of substance administered or absorbed, the way in which the substance is administered (inhalation, ingestion, topical application, injection) and distributed in time (single or repeated doses), the type and severity of injury, the time needed to produce the injury, the nature of the organism(s) affected, and other relevant conditions.
3. Measure of incompatibility of a substance with life: this quantity may be expressed as the reciprocal of the absolute value of median lethal dose (1/LD50) or concentration (1/LC50)
RT acute toxicity, chronic toxicity, subacute toxicity, subchronic toxicity
toxicity equivalency factor (TEF): Factor used in risk assessment to estimate the toxicity of a complex mixture, most commonly a mixture of chlorinated dibenzo-p-dioxins, furans and biphenyls: in this case, TEF is based on relative toxicity to 2,3,7,8 -tetrachlorodibenzo-p-dioxin (TEF = 1) (#IUPAC)

toxicity equivalent (TEQ): Contribution of a specified component (or components) to the toxicity of a mixture of related substances (#IUPAC)

toxicity test: Experimental study of the adverse effects of exposure of a living organism to a substance for a defined duration under defined conditions
RT acute toxicity test, carcinogenicity test, chronic toxicity test, subchronic toxicity test (#IUPAC)

toxic material: See SN toxic substance (#IUPAC)

toxicodynamics: Process of interaction of potentially toxic substances with target sites, and the biochemical and physiological consequences leading to adverse effects
RT adverse effect, pharmacodynamics, target (#IUPAC)

toxicogenetics: Study of the influence of hereditary factors on the effects of potentially toxic substances on individual organisms
RT ecogenetics, pharmacogenetics, polymorphism (#IUPAC)

toxicokinetics: Process of the uptake of potentially toxic substances by the body, the biotransformation they undergo, the distribution of the substances and their metabolites in the tissues, and the elimination of the substances and their metabolites from the body. Both the amounts and the concentrations of the substances and their metabolites are studied. The term has essentially the same meaning as pharmacokinetics, but the latter term should be restricted to the study of pharmaceutical substances
BT chemobiokinetics
RT biotransformation, pharmacokinetics
WHO, 1979 (#IUPAC)

toxicological data sheet: Document that gives in a uniform manner data relating to the toxicology of a substance, its production and application, properties and methods of identification; the data sheet may also include recommendations on protective measures
PS toxicological profile, toxicological dossier
IRPTC, 1982 (#IUPAC)

toxicology: Scientific discipline involving the study of the actual or potential danger presented by the harmful effects of substances (poisons) on living organisms and ecosystems, of the relationship of such harmful effects to exposure, and of the mechanisms of action, diagnosis, prevention and treatment of intoxications
NT chemical toxicology (#IUPAC)

toxicological profile: An ATSDR document that examines, summarizes, and interprets information about a hazardous substance to determine harmful levels of exposure and associated health effects. A toxicological profile also identifies significant gaps in knowledge on the substance and describes areas where further research is needed (#ASTDR)

toxicometry: Term sometimes used to indicate a combination of investigative methods and techniques for making a quantitative assessment of toxicity and the hazards of potentially toxic substances (#IUPAC)

toxicophobia: Morbid dread of poisons
RT chemophobia (#IUPAC)

toxicophoric (toxophoric) group|Toxiphoric Group]: Structural moiety that upon metabolic activation exerts toxic effects: the presence of a toxicophoric group indicates only potential and not necessarily actual toxicity of a drug or other substances
SN toxogenic group (#IUPAC)

toxicovigilance: Active process of identification, investigation, and evaluation of various toxic effects in the community with a view to taking measures to reduce or control exposure(s) involving the substance(s) which produces these effects (#IUPAC)

Toxic Release Inventory (TRI): Database of toxic releases in the United States compiled from Superfund Amendments and Reauthorization Act of 1986 (SARA) Title III Section 313 reports.(1) (#CEHN)

toxic substance: Material causing injury to living organisms as a result of physicochemical interactions
SN chemical etiologic agent, poison, toxicant, toxic chemical, toxic material (#IUPAC)

toxification: Metabolic conversion of a potentially toxic substance to a product that is more toxic (#IUPAC)

toxin: Poisonous substance produced by a biological organism such as a microbe, animal or plant
PS venom (#IUPAC)

toxinology: Scientific discipline involving the study of the chemistry, biochemistry, pharmacology and toxicology of toxins
RT toxicology, toxin (#IUPAC)

toxogenic group: See SN toxicophoric group (#IUPAC)

1. Means by which something may be followed; for example a radioactive isotope may replace a stable chemical element in a toxic compound enabling the toxicokinetics to be followed.
2. Labelled member of a population used to measure certain properties of that population
Gold, Loening, McNaught and Sehmi, 1987
transcription: Process by which the genetic information encoded in a linear sequence of nucleotides in one strand of DNA is copied into an exactly complementary sequence of RNA
RT reverse transcription (#IUPAC)

1. Alteration of a cell by incorporation of foreign genetic material and its subsequent expression in a new phenotype
RT phenotype.
2. Conversion of cells growing normally to a state of rapid division in culture resembling that of a tumour.
3. Chemical modification of substances in the environment
Transgenerational effect: A health effect that occurs in the child or subsequent offspring of the person who is exposed to an environmental toxin/toxicant.(5) (CEHN)
transgenic: Adjective used to describe animals carrying a gene introduced by micro-injecting DNA into the nucleus of the fertilized egg (#IUPAC)

treatability: In relation to waste water, the amenability of substances to removal without adversely affecting the normal operation of biological treatment processes (such as a sewage treatment plant) (#IUPAC)

triage: Assessment of sick, wounded and injured persons following a disaster to determine priority needs for efficient use of available medical facilities (#IUPAC)

trophic level: Amount of energy in terms of food that an organism needs: organisms not needing organic food, such as plants, are said to be on a low trophic level, whereas predator species needing food of high energy content are said to be on a high trophic level. The trophic level indicates the level of the organism in the food chain
WHO, 1979 (#IUPAC)

tumorigenic: Able to cause tumours (#IUPAC)

1. Any abnormal swelling or growth of tissue, whether benign or malignant.
2. An abnormal growth, in rate and structure, that arises from normal tissue, but serves no physiological function
SN neoplasm

tumor progression: Sequence of changes by which a benign tumour develops from the initial lesion to a malignant stage (#IUPAC)

turnover time: See SN mean life (#IUPAC)


ulcer: Defect, often associated with inflammation, occurring locally or at the surface of an organ or tissue owing to sloughing of necrotic tissue (#IUPAC)

uncertainty factor:
1. In assay methodology, confidence interval or fiducial limit used to assess the probable precision of an estimate
2. In toxicology, value used in extrapolation from experimental animals to man (assuming that man may be more sensitive) or from selected individuals to the general population: for example,
o a value applied to the no-observed effect level (NOEL); or
o no-observed adverse effect level (NOAEL) to derive an acceptable daily intake or reference dose (RfD) (the NOEL or NOAEL is divided by the value to calculate the acceptable daily intake or RfD)
The value depends on the nature of the toxic effect, the size and type of population to be protected, and the quality of the toxicological information available
SN safety factor
RT modifying factor, no-observed-effect-level, no-observed-adverse-effect-level, reference dose (#IUPAC)

uncertainty factor: Mathematical adjustments for reasons of safety when knowledge is incomplete. For example, factors used in the calculation of doses that are not harmful (adverse) to people. These factors are applied to the lowest-observed-adverse-effect-level (LOAEL) or the no-observed-adverse-effect-level (NOAEL) to derive a minimal risk level (MRL). Uncertainty factors are used to account for variations in people's sensitivity, for differences between animals and humans, and for differences between a LOAEL and a NOAEL. Scientists use uncertainty factors when they have some, but not all, the information from animal or human studies to decide whether an exposure will cause harm to people also sometimes called a safety factor. (#ATSDR)

unit risk (as used by the USEPA): Incremental upper-boundary lifetime risk estimated to result from lifetime exposure to an agent if it is in air at a concentration of 1 mg/m3 or in the water at a concentration of 1 mg/L
IRIS, 1986 (#IUPAC)

upper boundary: Estimate of the plausible upper limit to the true value of a quantity: this is usually not a statistical confidence limit
IRIS, 1986 (#IUPAC)

uptake: Entry of a substance into the body, into an organ, into a tissue, into a cell, or into the body fluids by passage through a membrane or by other means
PS absorption (#IUPAC)

urgent public health hazard: A category used in ATSDR's public health assessments for sites where short-term exposures (less than 1 year) to hazardous substances or conditions could result in harmful health effects that require rapid intervention (#ATSDR)

urticaria: Vascular reaction of the skin marked by the transient appearance of smooth, slightly elevated patches (wheals, hives) that are redder or paler than the surrounding skin and often attended by severe itching (#IUPAC)

U.S. Department of Energy (DOE): The DOE administers federal energy research, development, regulation and policy. DOE is in charge of federal research on the storage and disposal of radioactive waste and can provide information to the public on radioactive waste disposal and management (#Glossary)

U.S. Department of Health and Human Services (HHS): HHS carries out federal health and social programs such as social security, human development, family support, health care financing and public health. The Public Health Service, a part of HHS, includes agencies such as the Centers for Disease Control, the Agency for Toxic Substances and Disease Registry, the Food and Drug Administration (FDA) and the National Institutes of Health. (#Glossary)

U.S. Environmental Protection Agency (EPA): The EPA enforces federal environmental protection laws. It registers and regulates pesticides, enforces laws covering outdoor air and drinking water quality and regulates the disposal of hazardous and solid wastes. EPA's Integrated Risk Information System (IRIS) is an electronic database containing information on health effects that may result from exposure to chemicals. IRIS is intended for those without extensive training in toxicology, but with some knowledge of health sciences. (#Glossary)

U.S. Food and Drug Administration (FDA): The FDA, part of the U.S. Department of Health and Human Services, carries out and enforces laws that protect the quality and safety of foods, food additives, cosmetics and medical drugs and devices. For example, the FDA monitors the quality of foods and drugs through product testing, and reviews food and drug ingredients, including pesticide residues, to determine if they pose health hazards. (#Glossary)

USGS: See "US Geological Survey" (#Glossary)

U.S. Geological Survey (USGS): The USGS, part of the U.S. Department of the Interior, identifies the nation's land, water, mineral and energy resources. USGS conducts research, prepares topographic maps and collects and interprets data on mineral and water resources. (#Glossary)


vacuole: Membrane-bound cavity within a cell (#IUPAC)

validity (of a measurement): Expression of the degree to which a measurement measures what it purports to measure
NT concurrent validity, construct validity, content validity, criterion validity, predictive validity.
Last, 1988 (#IUPAC)

validity of a study: Degree to which the inferences drawn from a study, especially generalizations extending beyond the study sample, are warranted when account is taken of the study methods, the representativeness of the study sample, and the nature of the population from which it is drawn
Last, 1988
NT external validity, internal validity (#IUPAC)

vasoconstriction: Decrease of the calibre of the blood vessels leading to a decreased blood flow
AN vasodilation (#IUPAC)

vasodilation: Increase in the calibre of the blood vessels, leading to an increased blood flow
AN vasoconstriction (#IUPAC)

vehicle: Substance(s) used to formulate active ingredients for administration or use (general term for solvents, suspending agents, etc.)
Brown, 1988
RT excipient (#IUPAC)

venom: Animal toxin generally used for self-defence or predation and usually delivered by a bite or sting
PS toxin (#IUPAC)

1. Process of supplying a building or room with fresh air
2. Process of exchange of air between the ambient atmosphere and the lungs
3. In physiology, the amount of air inhaled per day
4.oxygenation of blood

ventricular fibrillation: Irregular heartbeat characterized by uncoordinated contractions of the ventricle (#IUPAC)

vermicide: Substance intended to kill worms (#IUPAC)

vermifuge: Substance that causes the expulsion of intestinal worms (#IUPAC)

vertigo: Dizziness; an illusion of movement as if the external world were revolving around an individual or as if the individual were revolving in space (#IUPAC)

1. adj., Producing blisters on the skin.
2. n., Substance that causes blisters on the skin

1. Small sac or bladder containing fluid
2. Blisterlike elevation on the skin containing serous fluid

volatile: Evaporating readily at normal temperatures and pressures. The air concentration of a highly volatile chemical can increase quickly in a closed room. (#Glossary)

Volatile Organic Compounds (VOCs): Organic compounds that evaporate readily into the air. VOCs include substances such as benzene, toluene, methylene chloride, and methyl chloroform. (#ATSDR)

volume of distribution: Apparent (hypothetical) volume of fluid required to contain the total amount of a substance in the body at the same concentration as that present in the plasma assuming equilibrium has been attained
RT plasma (#IUPAC)


waste: Anything that is discarded deliberately or otherwise disposed of on the assumption that it is of no further use to the primary user (#IUPAC)

wasting syndrome: Disease marked by weight loss and atrophy of muscular and other connective tissues that is not directly related to a decrease in food and water consumption (#IUPAC)

water quality criteria: Levels of water quality expected to render a body of water suitable for its designated use. Criteria are based on specific levels of pollutants that would make the water harmful if used for drinking, swimming, farming, fish production, or industrial processes.(1) (#CEHN)

weibull model: Dose-response model of the form:
P(d) = 1 - exp(-bdm)
Where P(d) is the probability of cancer death due to a continuous dose rate, d, b and m are constants.
IRIS, 1986 (#IUPAC)

weight-of-evidence for toxicity: Extent to which the available biomedical data support the hypothesis that a substance causes a defined toxic effect such as cancer in humans.
IRIS, 1986 (#IUPAC)

WHO: See World Health Organization (#Glossary)

withdrawal effect: Adverse event following withdrawal from a person or animal of a drug to which they have been chronically exposed or on which they have become dependent (#IUPAC)

wood-burning-stove pollution: Air pollution caused by emissions of particulate matter, carbon monoxide, total suspended particulates, and polycyclic organic matter from wood-burning stoves.(1) (#CEHN)

wood treatment facility: An industrial facility that treats lumber and other wood products for outdoor use. The process employs chromated copper arsenate (CCR), which is regulated as a hazardous material.(1) (#CEHN)

World Health Organization (WHO): WHO, an agency of the United Nations, carries out public and environmental health programs throughout the world. For example, WHO trains health personnel and assists countries to provide primary health care, prevent communicable diseases and combat malnutrition. WHO has developed international guidelines for pesticide residues in foods and chemicals in drinking water. (#Glossary)

working zone: Space measuring up to 2 m over the level of the floor or platform that contains a worker's permanent or temporary station.
IRPTC, 1982 (#IUPAC)


x-disease: Hyperkeratotic disease in cattle following exposure to chlorinated dibenzo-p-dioxins, naphthalenes and related compounds (#IUPAC)

1. Strictly, any substance interacting with an organism that is not a natural component of that organism.
SN exogenous substance, foreign substance or compound.
2. Man-made compounds with chemical structures foreign to a given organism.
Nagel et al. (eds), 1991
SN anthropogenic substance.
zoocide: Substance intended to kill animals (#IUPAC)


1. Cell such as a fertilized egg resulting from the fusion of two gametes.
2. Cell obtained as a result of complete or partial fusion of cells produced by meiosis.
Nagel et al. (eds), 1991 (#IUPAC)

Sources Consulted

"ATSDR Glossary of Terms." Agency for Toxic Subtances and Disease Registry. Department of Health
and Human Services. 18 Jan. 2008 <[http://www.atsdr.cdc.gov/glossary.html#G-A-| http://www.atsdr.cdc.gov/glossary.html#G-A-]>.

"CEHN: Glossary of Children's Environmental Health Terms." Resource Guide. 2004. Children's
Environmental Health Network. 18 Jan. 2008. <[http://www.cehn.org/cehn/resourceguide/

"Glossary of Environmental Health Terms." Department of Health. 2006. New York State. 18 Jan. 2008.

"International Union of Pure and Applied Chemistry: Clinical Chemistry Division: Commission on
Toxicology: Glossary for Chemists of Terms Used in Toxicology: IUPAC Recommendations
1993." Pure and Appl. Chem Vol. 65 No 9. 1993: 2003-2122. Environmental Health and
Toxicology SIS Specialized Information Services. United States National Library of Medicine.
18 Jan. 2008. <[http://sis.nlm.nih.gov/enviro/glossarymain.html| http://sis.nlm.nih.gov/enviro/glossarymain.html]>.

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