Prenatal, infant exposure to pesticides ups risk of autism spectrum disorder
Exposure to ambient pesticides within 2,000 m of the mother’s residence during pregnancy increases the risk of autism spectrum disorder (ASD) in offspring, suggests a study. Moreover, risks for ASD with comorbid intellectual disability are further increased when infant is exposed to pesticides.
“Our findings suggest that risk of ASD increases with prenatal and infant exposure to several common ambient pesticides that have been shown to affect neurodevelopment in experimental studies,” researchers said.
An association was found between ASD risk and prenatal exposure to glyphosate (odds ratio [OR], 1.16; 95 percent CI, 1.06–1.27), chlorpyrifos (OR, 1.13; 1.05–1.23), diazinon (OR, 1.11; 1.01–1.21), malathion (OR, 1.11; 1.01–1.22), avermectin (OR, 1.12; 1.04–1.22) and permethrin (OR, 1.10; 1.01–1.20). [BMJ 2019;364:l962]
Estimated ORs for ASD with intellectual disability were higher by approximately 30 percent for prenatal exposure to glyphosate (OR, 1.33; 1.05–1.69), chlorpyrifos (OR, 1.27; 1.04–1.56), diazinon (OR, 1.41; 1.15–1.73), permethrin (OR, 1.46; 1.20–1.78), methyl bromide (OR, 1.33; 1.07–1.64) and myclobutanil (OR, 1.32; 1.09–1.60); this risk was further increased by up to 50 percent for some pesticide substances when infant was exposed in the first year of life.
“Environmental toxicants have been suspected to increase the risk of ASD, with available research suggesting associations between air pollution and the disorder,” according to researchers. [Environ Health Perspect 2013;121:380-386; Epidemiology 2014;25:851-858; Epidemiology 2010;21:631-641; Environ Health Perspect 2013;121:978-984]
Experimental studies provide additional evidence. For instance, mice exposed in utero to chlorpyrifos had postnatal deficits in social behaviour and restricted interests while the behaviour of maternal mice was not affected. In a mouse model of autism, brain oxidative stress and prostaglandin E2 synthesis increased with prenatal exposure to chlorpyrifos. [Environmental health: a global access science source 2017;16:43; PLoS One 2015;10:e0121663]
“Oxidative stress and dysregulated immune responses are implicated in organophosphate-related toxicity and pathogenesis of ASD, suggesting a possible mode of action,” researchers noted. [J Neuroinflammation 2016;13:149]
The present population-based, case-control study was conducted in California’s main agricultural region, Central Valley, using 1998–2010 birth data from the Office of Vital Statistics. Researchers identified a total of 2,961 individuals with a diagnosis of ASD, including 445 with intellectual disability comorbidity. Controls derived from birth records were matched 10:1 by sex and birth year.
Prenatal and infant exposures to pesticides (measured as pounds of pesticides applied per acre/month within 2,000 m from the maternal residence) were estimated by integrating data from Pesticide Use Reporting into a geographic information system tool. Eleven high-use pesticides were selected for analysis a priori according to previous evidence of neurodevelopmental toxicity in vivo or in vitro.
“Further research should be translational and integrate experimental and epidemiological approaches to further elucidate underlying mechanisms in the development of the disorder,” researchers said. “However, from a public health and preventive medicine perspective, our findings support the need to avoid prenatal and infant exposure to pesticides to protect early brain development.”