Common Pesticides May Increase Autism Risk Near Farms

Is it dangerous to live too close to a farm? Image by Sgarton

Is it dangerous to live too close to a farm? Image by Sgarton

Perhaps you’ve always wanted to move where idyllic farmland surrounds wide open spaces; it seems like a great place to raise a family…or not.

Unless organic farms border the home you’re considering, rethink that move.

A recent study links pesticides commonly used in agricultural areas to an increased risk of autism in children whose mothers reported exposure to these chemicals before or during pregnancy.

The U.S. Rate of Autism is Approximately One in 68 Children

Scientists followed 970 two-to-five year olds diagnosed with autism spectrum disorder (ASD), a group of developmental disabilities that can cause significant social, communication and behavioral challenges.

The research, part of the Childhood Autism Risks from Genetics and the Environment (CHARGE) study, collected data over ten years on 970 California children diagnosed with ASD. Focused on subjects living within a two-hour drive from the Sacramento area, the study correlated all family addresses prior to and during pregnancy with poison applications listed in Pesticide Use Reports. They then calculated autism risks in relation to normally developing children of the same age.

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Approximately One-third of Subjects Lived Near Pesticide Applications

These families’ homes were located less than a mile from documented agricultural usage of toxins during the time the mother was pregnant with a child who was later diagnosed with ASD. Farms often use more than one insecticide at the same time, making the researcher’s task more complex. The scientists studied three classes of the most commonly used chemicals, using the criteria of having been applied within a mile radius of the homes during pregnancy.

Second and Third Trimester Exposures Were Associated With Risk

You may have heard that the first trimester is when your baby is most vulnerable, but problems can occur at other times as well.

The research surprised the scientists with evidence that pesticide harm was not confined to the first trimester of pregnancy alone, according to Janie F. Shelton, of the University of California at Davis and lead researcher for the study. The CHARGE scientists looked for any correlations between toxin applications and gestation in order to further pinpoint high risk timing:

  • Exposure to organophosphates was associated with a 60% increased risk of ASD, especially when applications took place during the third trimester of pregnancy.
  •  Exposure to chlorpyrifos, a specific type of organosphosphate, was also associated with developmental harm when applications took place during the second trimester of pregnancy.
  •  Exposure to pyrethroids in the three months prior to conception, as well as for applications during the third-trimester, significantly increased ASD risk.
  •  Exposure to carbamates during pregnancy elevated risks that those children would suffer developmental delays.

Decoded Pregnancy asked Shelton for more information about these specific chemicals. She confirmed that they are all still currently in use, with newer, but not necessarily safer, pyrethroids replacing organophosphates for indoor use. Only organochlorine compounds like DDT have been gradually phased out, not so much because they were strongly linked with ASD in earlier studies but because of environmental concerns.

Previous Research Linked Exposure to Pesticides With Fetal Harm

Earlier studies measured metabolites in the mother’s urine, the levels of toxins in umbilical cord blood, or tested children born to mothers employed in the floriculture industry in Ecuador. Each concluded that there was an association between elevated risks for ASD and exposure to insecticides. The CHARGE study helped to confirm these findings.

In utero, a baby’s brain is developing nerve cells and synapses, finger-like structures that grow until they connect with another synapse, allowing the message from one cell to get to the next.

The development of firm connections is dependent partly on stimuli the baby receives in the prenatal environment, which is why experts believe that interacting with your unborn is important, and why some mothers sing, talk, read to and play with their babies before they are born.

In Insects, Paralysis and Death is the Result of Pesticide Exposure

When applied near the homes of pregnant women, however, pesticides may interfere with the growth and development of fetal nerve cells and synapses, disrupting signaling in the nervous system.

In the current study, the scientists evaluated only agriculture use, leaving the door open for more research on other potential sources of exposure, such as home and garden, schools or other institutions, and food. In addition, authors of the study suspect that some children could be more susceptible to toxins in the environment because of some poorly understood or as yet undiscovered genetic factors.

Limiting the Risks to Unborn Children

It is important to avoid direct exposure to insecticides while pregnant.

Scientists linked commonly-used agricultural chemicals to an increased risk of autism in children who live near farms. Heightened awareness of the dangers of pesticide exposure may help you to avoid or limit the risk to your unborn. Be alert to planned applications where you live and work, and consider choosing organic products whenever possible.


Shelton, Janie, et al. Neurodevelopmental Disorders and Prenatal Residential Proximity to Agricultural Pesticides: The CHARGE Study. (2014). Environmental Health Perspectives. Accessed on July 02, 2014

Centers for Disease Control and Prevention. Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years. (2014). Accessed on July 02, 2014

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