Animal study adds to evidence of link between pyrethroids and autism

A new animal study adds to evidence that prenatal exposure to common insecticides called pyrethroids may increase the likelihood of a child developing autism or another neurodevelopmental disorder.

Melissa Curtis and colleagues, who authored the study, note that earlier research has implicated pyrethroid exposure as a risk factor for autism, developmental delay, and neurodevelopmental disorders in general. They note, “Analysis of data from the CHARGE [Childhood Autism Risks from Genetics and the Environment] study showed a significant increase in risk for either ASD [autism spectrum disorder] or developmental delay from exposure during pregnancy to pyrethroid pesticides being applied up to 1.5 kilometers from the home. A regional study in New York showed an association between areas where aerial application of pyrethroid pesticides was used and ASD and developmental delay prevalence in the area. Additionally, the presence of pyrethroid metabolites in blood or urine correlates with risk for ADHD in children.”

In their own study, Curtis and colleagues investigated the effects of the pyrethroid chemical deltamethrin on the offspring of female mice exposed to the chemical during pregnancy or lactation. The researchers found that in addition to exhibiting alterations in the dopamine system in their brains, exposed mice had elevated levels of hyperactivity and repetitive behaviors, reduced vocalizations, and an increased likelihood of learning difficulties.

Study coauthor James Burkett says the symptoms of the offspring of exposed mice are similar to those exhibited by humans with neurodevelopmental disorders. He adds, “We’re not implying that these mice have autism or ADHD…. What we’re suggesting is that exposure to this insecticide has altered something in their brain, resulting in the same patterns of behavior that we witness in children with autism.”

Burkett comments, “Someone who comes and sprays in your house is most likely using [a pyrethroid insecticide]. It’s employed in landscaping and for mosquito fogging in streets. It’s ubiquitous. Nonetheless, our research further substantiates the notion that these substances may not be as harmless for kids and expectant mothers as we formerly assumed.”

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“Developmental pyrethroid exposure causes a neurodevelopmental disorder phenotype in mice,” Melissa A. Curtis, Rohan K. Dhamsania, Rachel C. Branco, Ji Dong Guo, Justin Creeden, Kari L. Neifer, Carlie A. Black, Emily J. Winokur, Elissar Andari, Brian G. Dias, Robert C. Liu, Shannon L. Gourley, Gary W. Miller, and James P. Burkett, PNAS Nexus, April 25, 2023 (free online). Address: James Burkett, james.burkett@utoledo.edu.

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“Research links common insecticide to neurodevelopmental disorders,” news release, University of Toledo, April 25, 2023.

This article originally appeared in Autism Research Review International, Vol. 37, No. 3, 2023