Exposure to Ambient Pesticides and Autism Spectrum Disorder Risk

by | Aug 19, 2019 | 2019, Autism, Infant and Children's Health, Pesticides and Solvents, Pregnancy and Lactation

Written by Joyce Smith, BS. Prenatal or infant exposure to eleven pesticides, including glyphosate, chlorpyrifos, diazinon, and permethrin, were associated with increased odds of developing autism spectrum disorders in children.

pregnancy - women's healthPrevious research has shown common pesticides to cause neurodevelopmental impairment 1-4. Increases in the prevalence of autism spectrum disorder (ASD) have directed attention to environmental factors that could contribute to risk. Studies using animal models have documented neurobehavioral abnormalities after pesticide exposure, and it has been suggested that organophosphates 5 and organochlorines 6 might increase autism risk. In a population-based study, 7 researchers used odds ratios,  95% confidence intervals and multivariable logistic regression to assess whether prenatal and infant exposure to 11 high-use pesticides, known to have neurodevelopmental toxicity, was associated with autism spectrum disorder (with or without intellectual disabilities) in offspring and adjusted for confounders.

The researchers examined detailed California records on pesticide use and registries for births and developmental services to geographically link pesticide use in agricultural counties to cases of autism diagnoses in those areas (2961 cases; 35,370 sex- and birth-year-matched controls). Reporting was integrated into a geographic information system tool to estimate prenatal and infant exposure to pesticides measured as pounds of pesticides applied per acre/month within 2000 meters from the maternal residence. Children with pervasive developmental disorder or Asperger disorder were not included; children with comorbid intellectual disability were analyzed separately. Analyses were adjusted for sociodemographics and traffic-related air pollution.

  • Six of the eleven pesticides were each found to be associated with about a 10% increase in autism risk compared with no exposure. These associations were weaker in analyses after adjusting for all 11 compounds.
  • Risk of autism spectrum disorder was associated with prenatal exposure to glyphosate (odds ratio 1.16, 95% confidence interval 1.06 to 1.27), chlorpyrifos (1.13, 1.05 to 1.23), diazinon (1.11, 1.01 to 1.21), malathion (1.11, 1.01 to 1.22), avermectin (1.12, 1.04 to 1.22), and permethrin (1.10, 1.01 to 1.20).
  • Regarding children with autism spectrum disorder plus intellectual disability, exposure to any of the above mentioned six pesticides during pregnancy or infancy increased the risk to an even greater extent (by 30%–40%).

This study reports an 8% background rate of autism spectrum disorder against a national USA CDC background rate of 1.5 % in 2012-2013 8. This difference may reflect a higher risk of ASD which may be more specific to the niche agricultural area of southern California investigated in this study and would not necessarily apply to non-agricultural areas of the country.

Case control studies such as this one only give us odds ratios that have no relationship to risk. This study does not prove causation, only a weak association. However, randomized controlled trials in this type of cohort cannot be done because of the associated risks of pesticide use; therefore, observational studies such as this one have value.

This study found that exposure of pregnant women and infants to ambient pesticides within 2000 meters of their residence increases the risk of autism spectrum disorder in newborns and infants compared with women and offspring from the same agricultural region without such pesticide exposure.  From a public health and preventive medical perspective, these study findings support the need to avoid prenatal and infant exposure to pesticides to protect early brain development.

Source: von Ehrenstein, Ondine S., Chenxiao Ling, Xin Cui, Myles Cockburn, Andrew S. Park, Fei Yu, Jun Wu, and Beate Ritz. “Prenatal and infant exposure to ambient pesticides and autism spectrum disorder in children: population based case-control study.” bmj 364 (2019): l962.

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Posted August 19, 2019.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

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