Oil Dispersant

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This section of Toxipedia was created solely by Toxipedia staff.

Overview


Oil dispersants are a common tool used after oil spills to break up oil slicks on the water surface and increase the oil's rate of biodegradation. By breaking up large slicks, oil dispersants are intended to reduce harmful oil exposures of birds, fish, and other wildlife in proximity to spills. Two oil dispersant products were used heavily in the BP oil leak: COREXIT 9500 and 9527, both produced by Nalco. BP used over 1,800,000 gallons of dispersant since the start of the oil leak (Buchanan).

How Oil Dispersants Work

Oil dispersants work by separating an oil slick into small droplets of oil. Wind, waves, and other turbulence in the water break up these droplets and disperse them throughout the water column. Once dispersed, the oil droplets are consumed by naturally occurring bacteria or they are carried out into the open ocean. The goal of using oil dispersants is to protect fragile coatal areas from oil coming ashore.

Nalco Website and Video on How Oil Dispersants Work

The Chaos of Cleanup: Analysis of the Potenital Health and Environmental Impacts of Chemicals in Dispersant Products


Download the report today!

This report highlights key findings from research on the 57 chemicals found in the oil dispersant products listed for use by the EPA as appropriate for in response to oil spills. Additionally, the report disects issues of concern with the approval process for dispersant products and makes suggestions on improving regulations so that the safest dispersant is used in each unique spill.

Oil Dispersant Glossary


Throughout the oil dispersant section you may come across a word, phrase, or abbreviation that you are not familiar. Swing into the oil dispersant glossary for definitions and explanations of these terms.

Oil Dispersant Chemicals


There are a total of 57 chemical ingredients that are found in the oil dispersant products approved for use by the US Environmental Protection Agency. View a chart of the potential effects on human health and the aquatic environment.

Oil Dispersant Products


Click on a product name for information on the chemcials found in it, potential effects on human and environmental health, as well as data on its effectiveness at dispersing oil.

Environmental Toxicity


Oil dispersants begin to break down within 16 days of application in aquatic environments (CDC 2010).

Dispersing oil can have both positive and negative impacts on the environment and wildlife. "They expose marine life in the water column to more oil than would be the case for untreated oil, which floats at the surface" (Torrice 2010.) However, "Oil in the water column...won't reach wetlands on shore, where it could wreak greater havoc" (Torrice 2010).

The potential environmental impacts of oil dispersants are dependent on various factors, described below.

Species of Wildlife

  • Different species of aquatic wildlife react differently to oil dispersant exposure, as evaluated by the exposure level that causes a 50% mortality rate under particular exposure conditions. For example, grass shrimp can withstand exposure to higher concentrations of Corexit oil dispersants than the Pacific oyster. Analysis of tests done on a variety of species of aquatic life show that crustaceans (a group of animals including crabs, shrimp, and barnacles) are more sensitive to oil dispersant exposure than fish (George-Ares, 2000).
  • One study found that the species with the least amount of protective shell or external tissue are most sensitive to oil dispersant exposure (Scarlett et al., 2005).
  • Another study found that the use of oil dispersants increased the levels of hydrocarbons, which are found in crude oil, in rockfish. Fish exposed to high levels of hydrocarbons may show changes in their physiology. Study researchers state that similar effects could be seen in other ovoviviparous fish, fish that give birth to live young instead of eggs (Jung et al., 2009).
  • A study was performed to see if the use of oil dispersants affected fish intake of PAHs (polycyclic aromatic hydrocarbons, a chemical compound that exists in oil). Researchers found that the use of oil dispersants did in fact increase exposure and uptake of PAHs by fish, especially fish that live throughout the water column of coastal areas, the ocean, and lakes. They also state that "the risk of PAH toxicity ... especially to sensitive life stages such as eggs and larvae, is enhanced by chemical dispersion (Ramachandran et al., 2003)." "Concentrations of LMWPAHs and HMWPAHs (low and high weight PAHs) are higher in the water column following application of chemical dispersants to surface slicks" (Couillard et al. 2004).
    • PAHs have been studied and shown to cause cardiac problems, abnormal accumulations of fluid in the body, and spinal and cranial deformation of fish embryos (Incardona et al., 2004). Chronic exposure to PAHs has also been shown to cause increased rates of parasite infection, which may cause disease and death in fish.

Life Stage of Wildlife

  • Early life stages of aquatic organisms (embryo, larval, and juvenile) have a higher sensitivity to oil dispersants. The George-Ares study states, "Corexit 9500 and Corexit 9527 are moderately toxic to early life stages of fish, crustaceans, and molluscs." Studies have shown that the age, down to the hour, can have an impact on the species' level of sensitivity to oil dispersants. For example, "Herring eggs at time of fertilization were more sensitive to the dispersants ... than herring eggs 6 hours after fertilization" (the herring eggs were exposed to a different type of oil dispersant) (George-Ares, 2000).

Duration of Exposure

  • The longer the period of exposure to oil dispersants is, the worse the impacts on particular species can be. In several studies, species continually exposed to oil dispersants for a 96-hour period were more susceptible to a 50% mortality rate than species exposed to oil dispersants just one time. Releasing oil dispersants into the water for days, weeks, or months at a time will increase the dispersants' level of toxicity.
  • In a study that compared the toxicity of oil, dispersants, and oil plus dispersants on shrimp, minnows, and silverside fish, researchers found that oil plus a dispersant, in this case Corexit 9500, had an equal or lower toxicity than just the oil. However, this test was to reflect a one-time application of dispersant. When dispersant is continuously applied, effects of toxicity are more readily seen in the test species. The longer the dispersant is applied, the more toxic it becomes (Fuller et al., 2004).

Water Temperature

  • Studies have shown a direct correlation between water temperature and wildlife's sensitivity to oil dispersants. The warmer the water is, the more toxic the oil dispersants are to aquatic life. In studies, both grass shrimp and scallops were able to withstand significantly higher concentrations of oil dispersants in water at lower temperatures. A 10 to 20C degree increase in water temperature dramatically increased their sensitivity to oil dispersants (George-Ares 2000).
  • Current Gulf of Mexico Water Temperatures from NOAA

Concentration of Dispersant

  • The higher the concentration of oil dispersants in water, measured in parts per million (ppm), the more likely it is for the dispersants to affect wildlife. Certain species can withstand very high concentrations of oil dispersants, while others show negative impacts at very low concentrations. Negative effects on particular aquatic species have been shown to be reversible at low concentrations, but the higher the concentration, the more likely that the effects will be irreversible (Scarlett et al., 2005).
  • The maximum recorded concentration of oil dispersants in open water is 13ppm (Scarlett et al., 2005). Studies have shown that in many cases the oil dispersant concentrations are less than 1 ppm within hours of application (George-Ares 2000).

Geography and Type of Water Body

  • Areas where water is more stagnant or protected, such as estuaries, enclosed bays, and reefs, are more susceptible to high concentrations of oil dispersants than more open or large bodies of water.
  • Without wave action and turbidity, oil dispersants have a lower rate of dissipation (Scarlett et al., 2005).

References


Buchanan, Susan. "Dispersants Add to Gulf Spill's Toxi Threats." The Louisiana Weekly. 1 June 2010. Web. 01 June 2010. <http://www.louisianaweekly.com/news.php?viewStory=2862>.

"CDC - Oil Spill Response - Dispersant Information for Health Professionals." Centers for Disease Control and Prevention. 19 May 2010. Web. 03 June 2010. <http://emergency.cdc.gov/gulfoilspill2010/dispersants_hcp_info.asp>.

US EPA EPA Response to BP Spill in the Gulf of Mexico http://www.epa.gov/bpspill/

Fuller, Chris, James Bonner, Cheryl Page, Andrew Ernest, Thomas McDonald, and Susanne McDonald. "Comparative Toxicity of Oil, Dispersant, and Oil plus Dispersant to Several Marine Species." Environmental Toxicology and Chemistry 23.12 (2004): 2941-2949.

George-Ares, A., and J. R. Clark. "Aquatic Toxicity of Two Corexit Dispersants." Chemosphere 40 (2000): 897-906.

Incardona, John P., Tracy K. Collier, and Nathaniel L. Scholz. "Defects in Cardiac Function Preceded Morphological Abnormalities in Fish Embryos Exposed to Polycyclic Aromatic Hydrocarbons." Toxicology and Applied Pharmacology 196.2: 191-205.

Jung, Jee Hyun, Un Hyuk Yim, Gi Myeong Han, and Won Joon Shim. "Biochemical Changes in Rockfish, Sebastes Schlegeli, Exposed to Dispersed Crude Oil." Comparative Biochemistry and Physiology C.150 (2009): 218-23.

Ramachandran, Shahunthala D., Peter V. Hodson, Colin W. Khan, and Ken Lee. "Oil Dispersant Increases PAH Uptake of Fish Exposed to Crude Oil." Ecotoxicology and Environmental Safety 59 (2004): 300-08.

Scarlett, Alan, Tamara S. Galloway, Martin Canty, Emma L. Smith, Johanna Nilsson, and Steven J. Rowland. "Comparative Toxicity of Two Oil Dispersants, Superdispersant-25 and Corexit 9527, to a Range of Coastal Species." Environmental Toxicology and Chemistry 24.5 (2005): 1219-227.

Torrice, Michael. "Cleaning up the Gulf Oil Spill." Chemical and Engineering News 88.20 (2010):36-37.

Breaking News Stories


Oil Dispersant News from Environmental Health News


Environmental Health News
( Links to articles in today's press about environmental health. Many more links available today at www.EnvironmentalHealthNews.org )
Deepwater Horizon disaster continues to harm environment.
This week, as we mark the fourth anniversary of the April 2010 Deepwater Horizon oil spill, evidence of that catastrophe's effects on wildlife continues to emerge.
Industry failed to learn lessons from major oil spills.
Four years after the BP oil drilling disaster in the Gulf of Mexico, it's clear that wildlife, communities and the environment along the Gulf Coast continue to suffer lasting damage. ExxonMobil, BP and Shell have shown they have yet to learn the lesson we strive to teach our youngest children: safety first.
BP oil spill: Scientists struggling to understand effects four years later.
Four years after the BP Deepwater Horizon blowout and the uncontrolled release of as much as 200 million gallons of crude oil, scientists are still struggling to understand how the oil and the dispersant chemicals used to break it down have affected the environment.
Breaking down the myths and misconceptions about the Gulf Oil Spill.
In the months and years following the 2010 Deepwater Horizon oil spill, telling fact from fiction regarding seafood safety and ecosystem health was supremely difficult. To clear up some of the confusion, here are seven topics of concern, some still unresolved, about the Gulf Oil Spill.
Study finds high rates of depression, anxiety among Gulf oil spill cleanup workers.
Researchers studying the health of nearly 33,000 people who did clean up work during the 2010 Gulf of Mexico oil spill say it's still too early to tell what impact exposure to oil and dispersants will have on their bodies in the long-term. But early results show widespread symptoms of depression and anxiety.
Study follows BP oil spill workers.
Researchers studying the health of BP oil spill workers say it’s too early to draw solid conclusions, but they have seen an increase in anxiety and depression in those who helped cleaned up the mess.
Four years after spill, questions on long-term health.
Like so many Gulf Coast residents who pitched in after the April 20, 2010, explosion of the Deepwater Horizon rig, George Barisich was motivated by a desire to help and a need to make money - the oil had eviscerated his livelihood. Today he regrets that decision.
Aboud: Government covering up oil-spill damage.
Armed with a dead pelican and a catch of poisoned fish, secretary of Fishermen and Friends of the Sea Gary Aboud said Government was covering up the extent of the damage to marine life from the Petrotrin oil spill which had affected La Brea and environs since December 2013.
25 years after Exxon Valdez spill, oil remains and work is unfinished.
The real issue is whether increased dangers from "extreme oils," including deepwater oil and Arctic oil, tip the balance in favor of safer energy options. If sea otters and children could vote, that answer would favor independence from fossil fuels.
Louisiana's coastal insects still dying from BP oil spill, researcher says.
Insects living in wetland grasses along Louisiana's coast oiled in the aftermath of the 2010 BP Deepwater Horizon disaster are still dying, a result of exposure to remaining oil in the marsh almost four years later, according to a Louisiana State University entomologist.
Exxon Valdez taught lesson that prevention is key.
As Alaska nears the 25th anniversary of the Exxon Valdez oil spill, memories are still so raw that some Alaskans say they don’t want to recognize the date or remember the experience.
BP oil spill medical settlement moves forward.
It has been more than a year since the federal judge overseeing the sprawling BP oil spill litigation approved a settlement allowing for payments and treatment for hundreds of thousands of coastal residents and cleanup workers who said they were made ill.
More than three years later, oil from the Deepwater Horizon persists in the Gulf.
It’s now been more than three and a half years since the Deepwater Horizon oil drilling rig leased to BP exploded, causing over 200 million gallons of crude oil to spill into the Gulf of Mexico, the largest offshore oil spill in U.S. history.
Arctic oil spill is certain if drilling goes ahead, says top scientist.
A serious oil spill in the Arctic is a "dead cert" if drilling goes ahead, with potentially devastating consequences for the pristine region, according to a leading marine scientist who played a key role in analysis of BP's Deepwater Horizon oil spill.
What BP owes America.
BP is the sixth-largest corporation on the planet. It is not a victim; it’s on trial for its mistakes. At a time when many Americans wonder if too-big-to-fail corporations are above the law, we need to see that our bedrock environmental regulations are enforced because they were written for events just like the BP spill.
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