State of Science :: Pesticides
Update on Chlorpyrifos Use, Exposures, and Risk
An important new study in the November 2006 issue of the journal "Pediatrics" has documented significant adverse impacts on mental development, motor skills, and behavior among a group of three-year old children born to mothers exposed to the insecticide chlorpyrifos.
This study has raised questions about current uses and exposures to the organophosphate (OP) insecticide chlorpyrifos, as well as the impacts of a June 2000 agreement between the insecticide's manufacturer, Dow AgroSciences, and the U.S. Environmental Protection Agency (EPA).
Key questions will arise in placing this study's findings into perspective -
- Are pregnant women and their babies still at risk? And if so, from what sources of exposure?
- Did the EPA actions initiated in June 2000 to restrict certain chlorpyrifos uses solve the problem?
- Does this study's findings have relevance to EPA's risk assessment and regulatory actions?
- What more can be done, or needs to be done to reduce exposures to chlorpyrifos?
Pregnant women and babies are still at risk because of substantial, ongoing agricultural uses of chlorpyrifos. Based on data from the USDA's National Agricultural Statistics Service (NASS), chlorpyrifos use in 2005 has gone up marginally since the actions taken by the EPA in 2000 and 2001 to restrict certain chlorpyrifos crop uses including apples, grapes, and tomatoes. Farm use in 2005 and 2001 was just less than 5 million pounds on this set of major crop uses, as shown in the table "Chlorpyrifos Use on Selected Agricultural Crops in 2005 Compared to 2001."
While EPA actions have largely ended all residential uses of chlorpyrifos, exposures remain common through food. Each year the USDA's "Pesticide Data Program" collects 15,000 or more samples of foods commonly consumed by infants and children and tests them for pesticide residues. Based on results from 2004 PDP testing, chlorpyrifos residues remain common in the diet, especially in fresh fruits and vegetables. A set of tables have been developed reporting chlorpyrifos residues in four foods based on 2004 PDP results - strawberries, tomatoes, grapes, and sweet bell peppers.
The tables show and compare the percent of domestic and imported samples testing positive for chlorpyrifos. Mean residue levels, measured in parts per million, are also compared between positive domestic and imported samples. Across the four crops, imported produce was 16-times more likely to contain detectable levels of chlorpyrifos than domestic fruit and vegetables, and the mean levels of this insecticide were 2.8 times higher in imports compared to U.S. grown produce.
These results are further evidence of a worrisome trend - the shift of pesticide residues and risk from produce grown in the U.S. to imported produce. The extent of this shift and reasons leading to it are described in detail in the Center's "Critical Issue Report" on reducing pesticide dietary risks.
The Center will update and expand the analysis of pesticide levels in organic and conventionally grown food, and in imports versus domestic produce, in future reports. As the EPA considers the implications of the new study in "Pediatrics" on its regulatory assessment of chlorpyrifos, the surest way for women to avoid exposures to chlorpyrifos is by seeking out organic fruits and vegetables. Research on school-age children carried out by Dr. Alex Lu of Emory University has shown that after just a few days, an organic diet virtually eliminates dietary exposures to common organophosphate insecticides including chlorpyrifos and malathion. Dr. Lu's research is discussed in detail in the Center's reducing dietary exposures "Critical Issue Report."