Chlorpyrifos
Encyclopedia
Chlorpyrifos is a crystalline organophosphate
insecticide
that inhibits acetylcholinesterase
and is used to control insect pests. It is known by many trade names (see table). Chlorpyrifos is moderately toxic and chronic exposure has been linked to neurological effects, developmental disorders, and autoimmune disorders.
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). The crops with the most intense chlorpyrifos use are cotton, corn
, almond
s, and fruit trees including oranges and apples. It is produced via a multistep synthesis from 3-methylpyridine
.
Chlorpyrifos is normally supplied as a 23.5% or 50% liquid concentrate. The recommended concentration for direct-spray pin point application is 0.5% and for wide area application a 0.03 – 0.12% mix is recommended (US).
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. It is still widely used in agriculture, and Dow continues to market Dursban for home use in developing countries. In Iran, Dow claims Dursban is safe for people, and its sales literature claimed Dursban has "an established record of safety regarding humans and pets."
In 1995, Dow was fined US$732,000 for not sending the EPA reports it had received on 249 Dursban poisoning incidents, and in 2003, Dow agreed to pay US$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".
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.
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.
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.
, with potential for both acute toxicity
at larger amounts and neurological effects in fetuses and children even at very small amounts. For acute effects, the EPA classifies chlorpyrifos as Class II: moderately toxic. The oral LD50 for chlorpyrifos in experimental animals is 32 to 1000 mg/kg. The dermal LD50 in rats is greater than 2000 mg/kg and 1000 to 2000 mg/kg in rabbits. The 4-hour inhalation LC50 for chlorpyrifos in rats is greater than 200 mg/m3.
Chlorpyrifos poisoning has been described by New Zealand scientists as the likely cause of death of several tourists in Thailand who developed myocarditis
in 2011. Thai investigators have come to no conclusion as to what caused the deaths, but maintain that chlorpyrifos was not responsible, and that the deaths were not linked.
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 disorder
s such as ADHD. An earlier study demonstrated a correlation between prenatal chlorpyrifos exposure and lower weight and smaller head circumference at birth.
Among 50 farm pesticides studied, chlorpyrifos was one of two found to be associated with higher risks of lung cancer among frequent pesticide applicators than among infrequent or non-users. Pesticide applicators as a whole were found to have a 50% lower cancer risk than the general public, which is attributable to the nearly 50% lower smoking rate found among farm workers. However, applicators of chlorpyrifos had a 15% lower cancer risk than the general public, which the study suggests indicates a likely link between chlorpyrifos application and lung cancer.
A 2010 study found that each 10-fold increase in urinary concentration of organophosphate metabolites was associated with a 55% to 72% increase in the odds of ADHD in children.
Studies have shown evidence of "deficits in Working Memory Index and Full-Scale IQ as a function of prenatal CPF exposure [as measured when the children reach] 7 years of age."
A 2011 study on the neurotoxic effects of chlorpyrifos showed that chlorpyrifos and its more toxic metabolite, chlorpyrifos oxon, altered firing rates in the locus coeruleus. These results indicate that the pesticide may be involved in Gulf War Syndrome
and other neurodegenerative disorders.
found that its main breakdown product in the environment, chlorpyrifos oxon, is even more toxic to these animals.
The substance is very toxic for aquaculture (fish) and bee
s.
found TCPy
, a metabolite specific to chlorpyrifos, in the urine of 91% of people tested. An independent analysis of the CDC data claims that Dow has contributed 80% of the chlorpyrifos body burden of people living in the US. A 2008 study found dramatic drops in the urinary levels of chlorpyrifos metabolites when children switched from conventional to organic diets.
Air monitoring studies conducted by the California Air Resources Board
(CARB) have documented chlorpyrifos in the air of California communities. 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. Recent air monitoring studies in Washington and Lindsay, CA have yielded comparable results. 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, but a follow-up biomonitoring
study in Lindsay, CA has shown that people there have higher than normal chlorpyrifos levels in their bodies.
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.
Before it was banned from residential use in the US, chlorpyrifos was detected in 100% of personal indoor air samples and 70% of umbilical-cord blood collected from pregnant women 18–35 years old who self-identified as African American or Dominican and living in New York City public housing.
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
that inhibits acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...
and is used to control insect pests. It is known by many trade names (see table). Chlorpyrifos is moderately toxic and chronic exposure has been linked to neurological effects, developmental disorders, and autoimmune disorders.
Manufacture and use
Chlorpyrifos is manufactured by reacting 3,5,6-trichloro-2-pyridinol with diethylthiophosphoryl chloride.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
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA). The crops with the most intense chlorpyrifos use are cotton, corn
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...
s, and fruit trees including oranges and apples. It is produced via a multistep synthesis from 3-methylpyridine
3-Methylpyridine
3-Methylpyridine, or 3-picoline, is the organic compound with formula 3-CH3C5H4N. It is one of the three isomers of methylpyridine. This colorless liquid is a precursor to pyridine derivatives that have applications in the pharmaceutical and agricultural industries. Like pyridine, 3-methylpyridine...
.
Chlorpyrifos is normally supplied as a 23.5% or 50% liquid concentrate. The recommended concentration for direct-spray pin point application is 0.5% and for wide area application a 0.03 – 0.12% mix is recommended (US).
History
First registered in 1965 and marketed by Dow Chemical CompanyDow Chemical Company
The Dow Chemical Company is a multinational corporation headquartered in Midland, Michigan, United States. As of 2007, it is the second largest chemical manufacturer in the world by revenue and as of February 2009, the third-largest chemical company in the world by market capitalization .Dow...
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. It is still widely used in agriculture, and Dow continues to market Dursban for home use in developing countries. In Iran, Dow claims Dursban is safe for people, and its sales literature claimed Dursban has "an established record of safety regarding humans and pets."
In 1995, Dow was fined US$732,000 for not sending the EPA reports it had received on 249 Dursban poisoning incidents, and in 2003, Dow agreed to pay US$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".
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.
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.
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.
Health effects
Chlorpyrifos is an organophosphateOrganophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
, with potential for both acute toxicity
Acute toxicity
Acute toxicity describes the adverse effects of a substance that result either from a single exposure or from multiple exposures in a short space of time...
at larger amounts and neurological effects in fetuses and children even at very small amounts. For acute effects, the EPA classifies chlorpyrifos as Class II: moderately toxic. The oral LD50 for chlorpyrifos in experimental animals is 32 to 1000 mg/kg. The dermal LD50 in rats is greater than 2000 mg/kg and 1000 to 2000 mg/kg in rabbits. The 4-hour inhalation LC50 for chlorpyrifos in rats is greater than 200 mg/m3.
Chlorpyrifos poisoning has been described by New Zealand scientists as the likely cause of death of several tourists in Thailand who developed myocarditis
Myocarditis
Myocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...
in 2011. Thai investigators have come to no conclusion as to what caused the deaths, but maintain that chlorpyrifos was not responsible, and that the deaths were not linked.
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 disorder
Pervasive developmental disorder
Pervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...
s such as ADHD. An earlier study demonstrated a correlation between prenatal chlorpyrifos exposure and lower weight and smaller head circumference at birth.
Among 50 farm pesticides studied, chlorpyrifos was one of two found to be associated with higher risks of lung cancer among frequent pesticide applicators than among infrequent or non-users. Pesticide applicators as a whole were found to have a 50% lower cancer risk than the general public, which is attributable to the nearly 50% lower smoking rate found among farm workers. However, applicators of chlorpyrifos had a 15% lower cancer risk than the general public, which the study suggests indicates a likely link between chlorpyrifos application and lung cancer.
A 2010 study found that each 10-fold increase in urinary concentration of organophosphate metabolites was associated with a 55% to 72% increase in the odds of ADHD in children.
Studies have shown evidence of "deficits in Working Memory Index and Full-Scale IQ as a function of prenatal CPF exposure [as measured when the children reach] 7 years of age."
A 2011 study on the neurotoxic effects of chlorpyrifos showed that chlorpyrifos and its more toxic metabolite, chlorpyrifos oxon, altered firing rates in the locus coeruleus. These results indicate that the pesticide may be involved in Gulf War Syndrome
Gulf War syndrome
Gulf War syndrome or Gulf War illness describes a medical condition that affected veterans and civilians who were near conflicts during or downwind of chemical weapons depot demolition, after the 1991 Gulf War. A wide range of acute and chronic symptoms have included fatigue, musculoskeletal...
and other neurodegenerative disorders.
Effects on aquatic life and bees
Chlorpyrifos is highly toxic to amphibians, and a recent study by the United States Geological SurveyUnited States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
found that its main breakdown product in the environment, chlorpyrifos oxon, is even more toxic to these animals.
The substance is very toxic for aquaculture (fish) and bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s.
Exposure
A body burden study conducted by the Centers for Disease Control and PreventionCenters for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
found TCPy
TCPy
TCPy or 3,5,6-trichloro-2-pyridinol is a metabolite of chlorpyrifos and chlorpyrifos-methyl, both organophosphate insecticides. A study in Massachusetts reported a correlation between exposure to TCPy and lower testosterone levels in men. According to this source, exposure is "widespread" and of...
, a metabolite specific to chlorpyrifos, in the urine of 91% of people tested. An independent analysis of the CDC data claims that Dow has contributed 80% of the chlorpyrifos body burden of people living in the US. A 2008 study found dramatic drops in the urinary levels of chlorpyrifos metabolites when children switched from conventional to organic diets.
Air monitoring studies conducted by the California Air Resources Board
California Air Resources Board
The California Air Resources Board, also known as CARB or ARB, is the "clean air agency" in the government of California. Established in 1967 in the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor Vehicle Pollution Control Board, CARB is a department within the...
(CARB) have documented chlorpyrifos in the air of California communities. 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. Recent air monitoring studies in Washington and Lindsay, CA have yielded comparable results. 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, but a follow-up biomonitoring
Biomonitoring
Aquatic biomonitoring is the science of inferring the ecological condition of rivers, lakes, streams, and wetlands by examining the organisms that live there...
study in Lindsay, CA has shown that people there have higher than normal chlorpyrifos levels in their bodies.
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.
Before it was banned from residential use in the US, chlorpyrifos was detected in 100% of personal indoor air samples and 70% of umbilical-cord blood collected from pregnant women 18–35 years old who self-identified as African American or Dominican and living in New York City public housing.
External links
- Chlorpyrifos Technical Fact Sheet – National Pesticide Information Center
- Chlorpyrifos General Fact Sheet – National Pesticide Information Center
- Chlorpyrifos Pesticide Information Profile – Extension Toxicology Network
- EPA's Chlorpyrifos Page
- Dow's Chlorpyrifos Page
- Pesticideinfo.org's Chlorpyrifos Page
- Chlorpyrifos Information