A University of Washington study suggests that pesticides are finding their way into the bodies of pre-school children in agricultural communities at a higher level than previously thought.
More than half of the tested children of farm workers who live in Douglas and Chelan counties in Washington state were exposed during the spraying season to pesticide levels that exceeded federal safety levels, according to UW researchers. That's even though the children themselves do not work in the fields.
These levels were estimated from concentrations of pesticide breakdown products in urine, and compared to reference values established by the U.S. Environmental Protection Agency (EPA) and the World Health Organization. Doses were evaluated by assuming that breakdown products were attributable to either azinphos-methyl or phosmet, the two organophosphate pesticides used most frequently in the region.
Of children in the sample group, 56 percent had test results that indicated that exposures to azinphos-methyl, a chemical used to treat apple orchards, might exceed federal levels. The rate of higher exposure among children who lived more than a quarter mile from orchards, and whose parents were not farm workers, was 44 percent.
Researchers found different results when the exposures were attributed to phosmet, a less toxic chemical sometimes used as an alternative to azinphos-methyl. Only 9 percent of the farmworker children had test results suggesting that federal safety guidelines for phosmet might have been exceeded; none of the neighbor children did.
It's not known how and if these exposures are affecting children's health. The study concludes that regulators need to look at exposure standards and determine if they are appropriate, says one of the study authors, Richard Fenske, a professor of environmental health in UW's School of Public Health and Community Medicine. He is also director of UW's Pacific Northwest Agricultural Safety and Health Center.
Of the sample group, 91 children came from households with pesticide applicators or field-based workers; 18 children came from households with no direct link to agriculture. Researchers gathered urine samples during the spring and summer when apple orchards in the area are sprayed to attack coddling moth, the primary insect pest for apples in the region. "Exposures may have been higher at this time of year, and were probably the result of both direct exposure to pesticides and to pesticide residues in food," Fenske said.
The study by Fenske and colleagues will be published in the June issue of Environmental Health Perspectives. This journal is published by the National Institute of Environmental Health Sciences, one of the National Institutes of Health.
The EPA is in the midst of setting safety standards, specifically for children, for thousands of uses of chemicals. The pesticides involved in the UW study are organophosphates, a common class of pesticides that the EPA has targeted in its first efforts to implement tighter safety levels under a 1996 law.
Gauging children's aggregate exposure and cumulative risk to those pesticides is a tremendous task. There is considerable discussion about the best way to monitor exposure among children. Fenske and colleagues write that biological monitoring -- including the use of urine samples -- appears to be one useful component of an effective assessment program.
Other authors of the study include John C. Kissel, associate professor of environmental health; Chensheng Lu, research scientist in environmental health; David A. Kalman, professor and chair of environmental health; Nancy J. Simcox, research industrial hygienist; Emily H. Allen, research industrial hygienist; and Dr. Matthew C. Keifer, associate professor of medicine and environmental health.