Pesticide Exposure Linked to Autism Spectrum Disorder
Based on the sheer amount of research studies available dating back to the 1950s on the association between industrial chemicals and neurobehavioral disorders – it makes sense that more recent studies are finally starting to emphasize the chemical/neurodevelopmental disorder connection. That is, additional links to keynotes seen in Autism Spectrum Disorder (ASD) and ADHD symptomology.
Many agricultural pesticides are, after all, neurotoxic – that’s how they work on eradicating the intended pest. While regulatory and corporate entities continue to espouse their safety, and while farmers are encouraged to wear protective gear – how are levels of chemical plume to be regulated for individuals who live right near application sites?
What about the effects on the developing fetus?
UC Davis researchers in tandem with MIND Institute found a connection between pregnant women living in close proximity of California pesticide applications and later diagnoses of ASD and other developmental delays.
The large, multi-site California-based study, published in Environmental Health Perspectives, examined associations between specific classes of pesticides like organophosphates, pyrethroids and carbamates that were applied during the study participants’ pregnancies and later diagnoses of autism and developmental delay in their offspring. The associations were stronger when the exposures occurred during the second and third trimesters of the women’s pregnancies.
Researchers focused on areas with the heaviest pesticide applications – Sacramento Valley, Central Valley and the greater San Francisco Bay Area. They examined commercial pesticide application using the California Pesticide Use Report and linked the data to the residential addresses of approximately 1,000 participants in the Northern California-based Childhood Risk of Autism from Genetics and the Environment (CHARGE) Study. The study includes families with children between 2 and 5 diagnosed with autism or developmental delay or with typical development.
Twenty-one chemical compounds were identified in the organophosphate class, including chlorpyrifos, acephate and diazinon. The second most commonly applied class of pesticides was pyrethroids, one quarter of which was esfenvalerate, followed by lambda-cyhalothrin permethrin, cypermethrin and tau-fluvalinate. Eighty percent of the carbamates were methomyl and carbaryl.
For the study, researchers used questionnaires to obtain study participants’ residential addresses during the pre-conception and pregnancy periods. The addresses then were overlaid on maps with the locations of agricultural chemical application sites based on the pesticide-use reports to determine residential proximity. The study also examined which participants were exposed to which agricultural chemicals.
Principal investigator Irva Hertz-Picciotto said:
We mapped where our study participants’ lived during pregnancy and around the time of birth. In California, pesticide applicators must report what they’re applying, where they’re applying it, dates when the applications were made and how much was applied.
What we saw were several classes of pesticides more commonly applied near residences of mothers whose children developed autism or had delayed cognitive or other skills.
In the duration of this study, it was determined that one-third of CHARGE Study participants lived within one mile of commercial pesticide application sites. The ASD associations were greater for mothers living closer to application sites, and lessened the farther away they lived.
Organophosphates applied during the full course of pregnancy signaled greater risk of a child’s ASD diagnosis – especially for chlorpyrifos applications in the second trimester; Pyrethroids were moderately associated with autism spectrum disorder immediately before conception and in the third trimester; and Carbamates applied during pregnancy were associated with developmental delay.
They found that because the pesticides are neurotoxic, in utero exposures during early development could distort the complex processes of structural development and neuronal signaling, producing alterations to the excitation and inhibition mechanisms that govern mood, learning, social interactions and behavior – keynotes of ASD and those associated with ADHD symptomology.
In that early developmental gestational period, the brain is developing synapses, the spaces between neurons, where electrical impulses are turned into neurotransmitting chemicals that leap from one neuron to another to pass messages along. The formation of these junctions is really important and may well be where these pesticides are operating and affecting neurotransmission.
She notes the difficulty in reducing this type of risk, wishing for the open dialogue of ASD-risk and chemical exposures at both the societal and individual level, and emphasizing pre-natal nutrition. Her name appears on a lot of similar studies – perhaps this is what prompted her to say that she herself would not want her family to live near where pesticides are applied.