The researchers found that workers who thinned orchards were more likely to have detectable levels of pesticides in their house and vehicle dust as compared to agricultural workers who did not perform orchard thinning. The study also found that children of thinners were more likely to have detectable levels of pesticide metabolites in their urine than children on non-thinners. These findings support the theory that agricultural workers may track home pesticides on their clothing and shoes.
"Most previous pesticide-exposure research on farm workers has focused on pesticide handlers, such as pesticide mixers, loaders and sprayers, but this study suggests that more research is needed regarding exposure patterns among other types of farm workers as well," said Gloria Coronado, Ph.D., lead author and staff scientist in Fred Hutchinson's Cancer Prevention Program.
The study revealed that approximately 20 percent more thinners had pesticide residue in their home and vehicle dust as compared to non-thinners. The researchers also found that the presence of a dimethyl urinary pesticide metabolite called DMTP was present in children of thinners 10 percent more than in children of non-thinners.
Orchard thinners are thought to be at higher risk for pesticide exposure because thinning usually takes place in the spring, when crops are being sprayed to prevent pests. Such workers also have substantial physical contact with fruits, leaves, twigs and branches that may contain pesticide residues. In addition, unlike pesticide handlers, thinners are not required by the EPA to use protective equipment or undergo safety training.
"Unfortunately, we do not know the extent to which ongoing, low-level exposure to pesticides leads to adverse health consequences," said project leader Beti Thompson, Ph.D., a member of Fred Hutchinson's Public Health Sciences Division. "However, knowing exposure pathways helps us plan interventions to reduce exposure risk, which is particularly important for young children."
Children are uniquely susceptible to home-pesticide exposure because they spend greater amounts of time on carpets and floors, often wear minimal clothing during the summer spray season (increasing their likelihood of skin exposure) and engage in hand-to-mouth behavior (increasing their likelihood of ingesting pesticides).
"Children are not small adults," Thompson said. "With less-developed immune systems and adults, children may be less able to clear pesticides from their bodies."
The project, conducted in Eastern Washington's Lower Yakima Valley, involved 571 farm workers in 24 communities and labor camps who were interviewed about their pesticide-exposure patterns. Dust samples from households and vehicles of 213 randomly selected study participants were checked for the presence of six pesticides. Urine samples from these workers and family members (one adult and one child per household) were analyzed for the presence of five pesticide by-products.