Little is known about the environmental causes of autism. Pesticides affect numerous targets in the CNS, and cross the placenta. One revious report linked autistic symptoms to personal organophosphate pesticide exposures; another found an associaton with residential proximity to ganochlorine pesticide applications.
To compare early life exposures to household pesticides in young children with autism vs. typically developing controls.
Participants were from the CHARGE (Childhood Autism Risks from Genetics and the Environment) study, a large population-based case-control study in California, a central project within the UC Davis Center for Children's Environmental Health. Autism spectrum disorders (ASD) were confirmed using the Autism Diagnostic Inventory, an interview with the mother, and the Autism Diagnostic Observation Scale, a structured play activity session with the child. Mothers were 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.
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].
The higher prevalence of pet shampoo use by 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 on pets. Early life exposure to pyrethrins has been shown to compromise the blood-brain barrier in rodents, raising concern about prenatal and early postnatal exposures.