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Chlorpyrifos: Wikis


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CAS number 2921-88-2 Yes check.svgY
PubChem 2730
ChemSpider 2629
Molecular formula C9H11Cl3NO3PS
Molar mass 350.59 g/mol
Density 1.398 g/cm3 (43.5 °C)
Melting point

42 °C[1]

Solubility in water 2 mg/L (25 °C)
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Chlorpyrifos is a crystalline organophosphate insecticide that inhibits acetylcholinesterase and is used to control insect pests. Trade names include Brodan, Detmol UA, Dowco 179, Dursban, Empire, Eradex, Lorsban, Paqeant, Piridane, Scout, and Stipend. Chlorpyrifos is moderately toxic and chronic exposure has been linked to neurological effects, developmental disorders, and autoimmune disorders.


Manufacture and use

Chlorpyrifos are made from 3-picoline via a multistep route:[2]

1) Ammoxidation of 3-methylpyridine:

3-CH3C5H4N + 1.5 O2 + NH3 → 3-NCC5H4N + 3 H2O

2) hydrolysis of 3-cyanopyridine:

3-CH3C5H4N + 1 H2O → 3-H2NC(O)C5H4N

3) Decarbonylation of pyridine-3-carboxamide to 3-aminopyridine:

3-H2NC(O)C5H4N + NaOCl → 3-H2NC5H4N + CO2 + NaCl

4) Conversion to 3-hydroxypyridine:

3-H2NC5H4N + NaNO2 → 3-HOC5H4N + NH3

5) chlorination:

3-HOC5H4N + 3 Cl2 → 3-HO-2,5,6-Cl3C5HN + 3 HCl

In the US, chlorpyrifos is registered only for agricultural use, where it is "one of the most widely used organophosphate insecticides," according to the United States Environmental Protection Agency (EPA).[3] The crops with the most intense chlorpyrifos use are cotton, corn, almonds, and fruit trees including oranges and apples.[4] It is produced via a multistep synthesis from 3-methylpyridine.


First registered in 1965 and marketed by Dow Chemical Company under the tradenames Dursban and Lorsban, chlorpyrifos was a well known home and garden insecticide, and at one time it was one of the most widely used household pesticides in the US. Facing impending regulatory action by the EPA, Dow agreed to withdraw registration of chlorpyrifos for use in homes and other places where children could be exposed, and severely restricted its use on crops. These changes took effect on Dec. 31, 2001.[5] It is still widely used in agriculture, and Dow continues to market Dursban for home use in developing countries. In India, Dow claims Dursban is safe for people,[6] and its sales literature claimed Dursban has "an established record of safety regarding humans and pets."[7]

In 1995, Dow was fined $732,000 for not sending the EPA reports it had received on 249 Dursban poisoning incidents, and in 2003, Dow agreed to pay $2 million - the largest penalty ever in a pesticide case - to the state of New York, in response to a lawsuit filed by the Attorney General to end Dow's illegal advertising of Dursban as "safe".[8]

On July 31, 2007, a coalition of farmworker and advocacy groups filed a lawsuit against the EPA seeking to end agricultural use of the chlorpyrifos. The suit claims that the continued use of chlorpyrifos poses an unnecessary risk to farmworkers and their families.[9]

In August 2007, Dow's Indian offices were raided by Indian authorities for allegedly bribing officials to allow chlorpyrifos to be sold in the country.[10]

In 2008, the National Marine Fisheries Service (NMFS) imposed 1000 ft buffer zones around salmon habitat to protect endangered salmon and steelhead species. Aerial applications of chlorpyrifos will be prohibited within these zones. [11]

Health effects

Chlorpyrifos is a neurotoxin and suspected endocrine disruptor, and it has been associated with asthma,[12] reproductive and developmental toxicity, and acute toxicity. For acute effects, the EPA classifies chlorpyrifos as Class II: moderately toxic. Recent research indicates that children exposed to chlorpyrifos while in the womb have an increased risk of delays in mental and motor development at age 3 and an increased occurrence of pervasive developmental disorders such as ADHD.[13] An earlier study demonstrated a correlation between prenatal chlorpyrifos exposure and lower weight and smaller head circumference at birth.[14]

Chlorpyrifos is highly toxic to amphibians, and a recent study by the United States Geological Survey found that its main breakdown product in the environment, chlorpyrifos oxon, is even more toxic to these animals. [15]


A body burden study conducted by the Centers for Disease Control and Prevention found TCPy, a metabolite specific to chlorpyrifos, in the urine of 91% of people tested.[16] An independent analysis of the CDC data claims that Dow has contributed 80% of the chlorpyrifos body burden of people living in the US.[17] A 2008 study found dramatic drops in the urinary levels of chlorpyrifos metabolites when children switched from conventional to organic diets.[18]

Air monitoring studies conducted by the California Air Resources Board (CARB) have documented chlorpyrifos in the air of California communities.[19] Analyses of the CARB data indicate that children living in areas of high chlorpyrifos use are often exposed to levels of the insecticide that exceed levels considered acceptable by the EPA.[20][21] Recent air monitoring studies in Washington and Lindsay, CA have yielded comparable results.[22][23] Grower and pesticide industry groups have argued that the air levels documented in these studies are not high enough to cause significant exposure or adverse effects,[24] but a follow-up biomonitoring study in Lindsay, CA has shown that people there have higher than normal chlorpyrifos levels in their bodies. [25][26]

A study of the effects of chlorpyrifos on humans exposed over time showed that people exposed to high levels have autoimmune antibodies that are common in people with autoimmune disorders. There is a strong correlation to chronic illness associated with autoimmune disorders after exposure to chlorpyrifos.[27]


  1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 3–126. ISBN 0849305942. 
  2. ^ Shinkichi Shimizu; Nanao Watanabe; Toshiaki Kataoka; Takayuki Shoji, Nobuyuki Abe, Sinji Morishita, Hisao Ichimura (2002). "Pyridine and Pyridine Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a22_399. 
  3. ^ Reregistration Eligibility Decision for Chlorpyrifos
  4. ^ NASS Agricultural Chemical Database
  5. ^ EPA's Chlorpyrifos Page
  6. ^ Islamic Republic News Agency, Feb 17th, 2007
  7. ^
  8. ^
  9. ^ Press Release: Lawsuit Challenges EPA on Deadly Pesticide, EarthJustice, July 31st, 2007.
  10. ^ CBI raids Dow Chemical's Indian subsidiary for graft. Monsters and Critics, August 21st, 2007.
  11. ^ "Federal Government Announces Plan to Protect Salmon from Pesticides". Earthjustice. Retrieved 2009-09-02. 
  12. ^ AOEC Exposure Codes
  13. ^ Rauh VA, et al., Pediatrics, 2006, 118, e1845-e1859
  14. ^ Whyatt RM, et al., Environmental Health Perspectives, 2004, 112, 1125-32
  15. ^ Breakdown Products Of Widely Used Pesticides Are Acutely Lethal To Amphibians, Study Finds, Science Daily, June 25, 2007, accessed July 2, 2006.
  16. ^ CDC Third National Exposure Report
  17. ^ "Chemical Trepass," Pesticide Action Network North America, 2004
  18. ^ Lu, Chensheng; Dana B. Barr, Melanie A. Pearson, and Lance A. Waller (2008). "Dietary Intake and Its Contribution to Longitudinal Organophosphorus Pesticide Exposure in Urban/Suburban Children". Environ. Health Perspect. published ahead of print. doi:10.1289/ehp.10912. 
  19. ^ CARB Chlorpyrifos Monitoring Studies
  20. ^ Lee et al., Environmental Health Perspectives, 2002, 110, 1175-1184
  21. ^ S Kegley et al., "Secondhand Pesticides," Pesticide Action Network North America, 2003
  22. ^ C Dansereau et al., "Poisons on the Wind," Farm Worker Pesticide Project, 2006
  23. ^ S Kegley et al., "Drift Catching In Lindsay, California," Pesticide Action Network North America, 2006
  24. ^ Heather Hansen, "Proper Pest Management Keeps Washington Fruit Crop Healthy," Seattle Post Intellegencer, Jan 19, 2007.
  25. ^ Douglas Fischer, "Toxins permeate Central Valley town," Tri-Valley Herald, May 15th, 2007.
  26. ^ Californians For Pesticide Reform, Airborne Poisons: Pesticides in Our Air, and in Our Bodies, May 16th, 2007.
  27. ^ Thrasher, Ph.D., Jack D.; Gunnar Heuser, M.D., Ph.D., Alan Broughton, M.D., Ph.D. (2002). "Immunological Abnormalities in Humans Chronically Exposed to Chlorpyrifos". Archives of Environmental Health, 2002, 57:181-187 2002 (57): 181-187. 

Corrected EPA Chlorpyrifos information:

External links



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