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Chlorpyrifos

[klawr-pir-uh-fos, klohr-]

Chlorpyrifos is a toxic crystalline organophosphate insecticide that inhibits acetylcholinesterase and is used to control insect pests. Trade names include Dursban (home and garden uses) and Lorsban (agricultural uses).

Uses

In the US, chlorpyrifos is registered only for agricultural use, where it is "one of the most widely used organophosphate insecticides," according to the EPA. The crops with the most intense chlorpyrifos use are cotton, corn, almonds, and fruit trees including oranges and apples.

History

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. 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, and its sales literature claimed Dursban has "an established record of safety regarding humans and pets.

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".

On July 31st, 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.

Health Effects

Chlorpyrifos is a neurotoxin and suspected endocrine disruptor, and it has been associated with asthma, 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. An earlier study demonstrated a correlation between prenatal chlorpyrifos exposure and lower weight and smaller head circumference at birth.

Chlorpyrifos is highly toxic to amphibians, and a recent study by the USGS found that its main breakdown product in the environment, chlorpyrifos oxon, is even more toxic to these animals.

Exposure

A body burden study conducted by the CDC 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 leves 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.