Naled

Overview


Naled is an organophosphate insecticide first registered for use as an "adulticide insecticide" in 1959 primarily to control adult mosquitoes (#EPA Pesticides - Mosquito Control, 2007). Naled breaks down into dichlorvos in both animals and in the environment and has many health effects, both chronic and acute (#Cox, 2002).

Topic editor


Sean Foley
Lead author:
Sean Foley



Just the facts


Physical Information

Name: Naled (1,2-dibromo-2,2-dichloroethyl dimethyl phosphate)

Trade Name: Dibrom

Manufacturer: AMVAC Chemical Corporation

Use: organophosphate insecticide

Source: synthetic chemistry

Recommended daily intake: none

Absorption: dermal, inhalation, and oral - most toxic when inhaled

Sensitive individuals: workers

Toxicity/symptoms: highly toxic, symptoms result from cholinesterase inhibition

Regulatory facts: reregistered for use in 2006

Environmental: toxic to many organisms

Chemical Structure



Structure retrieved from Pesticide Action Network (PAN).


Chemical Description


Technical grade naled is a colorless to yellow liquid of 93% purity with a slightly pungent aroma (#INCHEM, 1978). It is non-soluble in water but is rapidly hydrolyzed in water (#INCHEM, 1978).

Use and Application


About one million pounds are used annually in the United States with 70% used for controlling adult mosquitoes and the remaining 30% used on various agricultural purposes: cotton in California and Louisiana, alfalfa in Idaho and Oregon, and grapes in California (#Cox, 2002). Mosquito control programs conducted by state or local authorities, naled is applied from truck-mounted or aircraft-mounted sprayers as a "low-volume spray" which dispense very fine aerosol droplets that stay aloft and kill adult mosquitoes on contact (#EPA).

Like most other pesticides, naled only makes up a small percentage of the applied product and for mosquito control the maximum rate for application of active ingredient (naled) is 0.1 lb of active ingredient per acre. Inert Ingredients are in most pesticide applications and naled is no exception. Caroline Cox from the Northwest Coalition for Alternatives to Pesticides (NCAP) lists solvents in Dibrom that are listed as "inert ingredients":

  • Napthaline: which has been classified by the EPA as a "possible human carcinogen" because it has caused lung tumors in mice. It has also caused headaches, restlessness, lethargy, nausea, diarrhea, and anemia

  • 1,2,4-trimethylbenzene: it is a eye and skin irritant and a nervous system depressant that causes headaches, fatigues, nausea, and anxiety as well as asthmatic bronchitis.

Nearly all of the naled used is applied aerially and drift from the application is considered a problem because naled is also toxic to beneficial insects (#Cox, 2002). Contamination has been found as far away as 750 meters from the site of application in a University of Florida study which led to the suggestion that no-spray buffer zones be established to greater than 750 meters from "economically sensitive areas" (#Cox, 2002). Unfortunately the most toxic route of exposure is inhalation and the most common application is as a mist making inhalation the most likely route as well (#ATSDR, 2007).

Health Effects


Main Article: Cholinesterase Inhibitor

Naled's health effects stem from its cholinesterase inhibiting mechanisms which are common to all organophosphates. It is a "severe" skin and eye irritant and can be ingested on food or in water, but it is most harmful and potent if it is inhaled (#Cox, 2002). Toxicologists at the University of California found that naled when inhaled is twenty times more toxic to rats as opposed to when it is ingested (#Cox, 2002).

Chronic Effects
Studies conducted on dogs and rates showed that naled does cause chronic nervous system damage resulting in a mineralization of the spinal cord and decreased nervous system enzyme activity that led to partial paralysis (#Cox, 2002).

Environmental Effects


Naled is practically non-persistent in the environment but is very toxic to most organisms (#EXTOXNET, 1996).

Degredation and Mobility
Naled is broken down into dichlorvos and dichloroacetic acid through chemical hydrolysis and biodegredation but all rapidly dissipate in soil under normal conditions (#EPA IRED - Naled, 2002). They are possibly mobile, but they usually breakdown so rapidly that their not likely to leach into groundwater (#EPA IRED - Naled, 2002). Its half-life in water is around two days (#EXTOXNET, 1996).

Aquatic Organisms
The EPA states that "there are potential risks to marine fish and invertebrates; however they are not of major concern" (#EPA IRED - Naled, 2002) however, the same document goes on to state "The EPA does not have sufficient data to estimate chronic risks" (#EPA IRED - Naled, 2002). To the contrary Cox reports that it is "very highly toxic to lake trout; highly toxic to rainbow trout, cutthroat trout, and catfish; and moderately toxic to sunfish, minnow, and bass" (#Cox, 2002). It also is toxic to beneficial aquatic insects such as stoneflies (#Cox, 2006). The debate therefore lies with whether it is long enough in the environment to cause damage. The EPA also requires that crops with higher application rates not be around aquatic environments which also helps to limit naled's release into the water (#EPA RED - Naled, 2006).

Birds
Naled is moderately to highly toxic to many bird species especially Canadian geese (#EXTOXNET, 1996 and #Cox, 2002). It has also been shown to affect reproduction in Mallard ducks (#Cox, 2002).

Beneficial Organisms
It is toxic to bees and stoneflies (#EXTOXNET, 1996).

Endangered Species
Evaluations by several groups, including the EPA and the United States Fish and Wildlife Service (USFW), have concluded that the use of naled puts many endangered species at risk (#Cox, 2002). Acceptable levels of concern (LOC) for endangered species are exceeded in numerous occasions as evidenced by page 64 of EPA Re-registration review for Naled).

Precautions


From #EXTOXNET, 1993:
"Protective clothing must be worn when handling naled. Before removing gloves, wash them with soap and water. Always wash hands, face and arms with soap and water before smoking, eating or drinking."

Regulation


Naled was first registered int he Unites States in 1959 by AMVAC Chemical Corporation as an insecticide and acaracide (#Cox, 2002). It was granted "Interim Reregistration" in 2002 and then "Reregistered" in 2006 (#EPA Pesticides - Reregistration, 2007).

External Links


References



Agency for Toxic Substances and Disease Registry (ATSDR). "Toxicologic Information About Insecticides Used for Eradicating Mosquitoes (West Nile Virus Control) April 2005". This page was updated on 09/11/2007. Accessed 12-07-07.


Caroline Cox. "Insecticide Factsheet - Naled (Dibrom)". Journal of Pesticide Reform Fall 2002: 22(3), 16-21.


Extension Toxicology Network (EXTOXNET). "Pesticide Information Profile - Naled". Revised June, 1996. Accessed 12-07-07.


Extension Toxicology Network (EXTOXNET). "Pesticide Information Profile - Naled". Published 1993. Accessed 12-07-07.


Environmental Protection Agency (EPA)Pesticides: Reregistration. "Pesticide Reregistration Status for Organophosphates". Last updated on Wednesday, November 28th, 2007. Accessed 12-07-07.


Environmental Protection Agency (EPA) Pesticides: Mosquito Control. "Naled for Mosquito Control". Last updated on Monday, April 23rd, 2007. Accessed 12-07-07.


Environmental Protection Agency (EPA). "Interim Reregistration Eligibility Decision for Naled". January, 2002. Accessed 12-07-07.


International Programme on Chemical Safety (INCHEM). "DATA SHEETS ON PESTICIDES No. 39 - NALED". June, 1978. Accessed 12-07-07.

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