Household Pesticide Use in Relation to Autism

Irva Hertz-Picciotto, MPH, PhD, Public Health Sciences and the M.I.N.D. Institute, University of California at Davis, Dept PHS, Davis, CA 95616, Isaac N. Pessah, PhD, 3 Department of Veterinary Molecular Biosciences, University of California at Davis, M.I.N.D. Institute, One Shields Avenue, Davis, CA 95616, Robin Hansen, Pediatrics and the M.I.N.D. Institute, University of California at Davis, 2825, 50th Street, Sacramento, CA 95817, and Paula Krakowiak, MS, M.I.N.D. Institute, University of California at Davis, 2825 50th Street, Sacramento, CA 95817.

Background: Pesticides affect a number of targets in the CNS, and cross the placenta. One previous report suggests a link between maternal residential proximity to commercial organochlorine pesticide exposure during early prenatal life and the risk of autism. That study did not evaluate individual exposures to household pesticides.

Objectives: To examine household pesticide use during the prenatal period or early postnatal period in relation to autism.

Methods: Participants were from the CHARGE (Childhood Autism Risks from Genetics and the Environment study, a large population-based case-control study in California. Autism spectrum disorders were confirmed using the ADI and ADOS. Mothers were extensively interviewed regarding demographics, lifestyle, and prenatal and early postnatal exposures of the child. Questions addressed use of numerous household products, including insecticides for flies and ants, pet shampoos, and weed control products. Interview data were available for 333 ASD cases and 198 confirmed typically developing controls. Logistic regression models were adjusted for family socioeconomic status. An index exposure period was defined as three months prior to conception through the child's first year of life.

Results: Mothers of ASD children were twice as likely to report using pet shampoos for fleas or ticks during the index period as compared with control mothers: adjusted Odds Ratio (aOR) = 2.0, 95% Confidence Interval (CI) = [1.2, 3.6]. When examined by trimester, the strongest association was during the second trimester: aOR = 2.6, 95% CI = [1.3, 6.0].

Conclusions: The higher prevalence of self-reported use of pet shampoos by CHARGE study mothers of children with ASD could be due to reporting bias, although many other products did not show differences. Pyrethrins have largely replaced organophosphates for flea control, but early life exposure to pyrethrins has been shown to compromise the blood-brain barrier in rodents, raising concern about prenatal and early postnatal exposures.