Residential Proximity to Agricultural Pesticides and Cognitive and Behavioral Scores in the CHARGE Study

Background:  Studies of gestational exposures to organochlorine and organophosphate pesticides have suggested an association between exposure during pregnancy and the risk of an autism spectrum disorder. In California, commercial application of pesticides is recorded at the spatial resolution of one square mile (2.6 sq. km) in a publically available historical pesticide use report database by chemical type, date, and location.

Objectives:  To describe the levels of pesticide application around the home of families of children with and without developmental disorders.

Methods: Utilizing home address records from the CHARGE study we reconstructed the agricultural application during pregnancy within the range of 1500m (slightly less than one mile) of the home, and restricted analyses to the Alta and Valley Mountain Regional Center catchment areas (located in the Sacramento and Central Valley of California) (N=575) where agricultural pesticide use was most prevalent. We summed the pounds of pesticide applied per three months of pregnancy to create a cumulative exposure for each trimester.  Linear regression was used to estimate the relationship between each of four classes of pesticides (pyrethroids, organophosphates, organochlorines, and carbamates) and scores of the Mullen Scales of Early Learning (MSEL) and the Vineland Adaptive Behavioral Scales (VABS). 

Results:  All pesticide classes were inversely associated with decreased cognitive and adaptive behavior, but only the pyrethroid class was significantly so. Second trimester pyrethroid exposure (65 exposed) was associated with a 3.8 point decline in MSEL scores (p=0.03) and a 4 point decrease in the VABS (p=0.002) per 10lb increase in application after adjusting for the diagnostic class, regional center, child’s gender, mothers education, year of birth and weighting by sampling probability. 

Conclusions:  Preliminary results show residential proximity to greater amounts of commercially applied pyrethroid insecticides was associated with decreased scores of cognition and adaptive behavior in California.