As I wrote in a previous blog post, Autism Spectrum Disorders (ASDs) “originate” in utero, as we demonstrated five years ago. By retrospectively analyzing data collected in maternity wards (more than 150 non-genetic parameters) using machine learning, we can identify at birth nearly half of the babies who will have autism and all those who will not (Caly et al. 2021). This Pelargos project—currently undergoing validation in 5–6 university hospitals/maternity wards—is a world first and, if validated, will enable the early implementation of behavioral interventions, which are all the more effective when used early: understanding how the syndrome develops.
Pregnancy is an extremely vulnerable process because, as has been explained time and again, the mother’s brain and that of her fetus have very different properties and respond differently to the environment and to treatments.
Consequently, it is crucial to determine which factors may disrupt the normal course of this process, leading to long-term consequences—particularly in terms of neurological and psychiatric syndromes or disorders that may manifest years later. In fact, we have identified well over a hundred parameters and factors that increase the incidence of these neurodevelopmental syndromes. Here, we discuss pesticides and pollution, and we will revisit other factors in future blog posts. We will not revisit here the toxicity of pesticides—at least for the majority of them—to farmers, nor their link to cancers and Parkinson’s disease.
For example, in a study published in 2014, Shelton and colleagues (Shelton et al. 2015) conducted a study (“The Charge Study”) in which they examined pesticide applications (as recorded in California state registries) and their effects on 970 participants. The aim was to determine the possible relationship between living near a pesticide-treated field during pregnancy and the incidence of ASD, developmental disorders, or no effects (neurotypical). The study found that approximately one-third of the mothers lived near a pesticide-treated field. The researchers compared the amount of pesticides applied (in pounds), the distance from the field (1.25, 1.5, and 1.75 km), and their associations with autism in particular. The findings indicate that living near a field where organophosphates—in particular—are sprayed increases the incidence of autism by 60%; these figures are higher when exposure occurs during the 2nd or 3rd trimester of pregnancy, and specifically during the 2nd trimester for chlorpyrifos exposure.
Children whose mothers were near fields where pyrethroids were applied were more likely to have autism, especially during the third trimester and shortly before birth. It should be noted that approximately 100 million kg of pesticides are applied in the state of California.
In a similar study, the authors measured levels of dialkyl phosphate (DAP) pesticide metabolites in children’s urine and showed that, among 119 children, there was a significant association between high levels of these compounds and a diagnosis of ADHD (MF Bouchard et al. 2013). Other studies compare the effects of combinations of multiple pesticides on IQ deficits in 7-year-old children born at a maternity hospital located less than 1 km away (Coker et al. 2017). There is a significant decrease in IQ with certain clusters of pesticides and a lesser decrease with others. A meta-analysis of 1,056 publications highlights both the breadth of the data and the shift from more statistical approaches to those based on the mechanisms of pesticide effects, the activation of metabolite cascades, the induction of genetic mutations, and so on (Liu et al. 2026).
In fact, evidence is accumulating to draw policymakers’ attention to the dangers, particularly during pregnancy, and it is difficult to review it all in a single blog post. A brief summary of a call to action by leading experts states
“Children living in rural communities are exposed to specific environmental factors, many of which may have long-term adverse consequences for their health. Children are particularly vulnerable to these exposures due to their close interaction with the environment and their developing physiology. The authors describe three environmental risks in rural settings: smoke from wood-burning stoves, contaminants in well water, and agricultural pollutants. The contaminants associated with these exposures have, among other things, adverse effects on the respiratory system, neurological development, and the cardiometabolic system, and are carcinogenic. The authors recommend that pediatricians practicing in rural areas screen for these environmental exposures and provide tools and resources related to testing, risk mitigation, and medical monitoring” (Criswell et al. 2026).
Admittedly, these are epidemiological data and therefore open to debate from a mechanistic standpoint; nevertheless, they corroborate observations demonstrating the vulnerability of the developing brain. Rather than ignoring this research, more studies of this kind should be conducted, given that the time is not ripe for a reevaluation of industrial agriculture, which is considered indispensable.
That leaves the main conclusion: the idea that the brain develops without any interaction with its internal and external environments, and that the impact of “life’s circumstances” is incompatible with what we know about developmental biology, must be rejected. We will have to accept that simplifying a complex phenomenon has its limits. We must acknowledge the major role of the environment through the array of fundamental mechanisms it influences.
Sources:
- Coker, Eric, Robert Gunier, Asa Bradman, Kim Harley, Katherine Kogut, John Molitor, and Brenda Eskenazi. 2017. “Association between Pesticide Profiles Used on Agricultural Fields near Maternal Residences during Pregnancy and IQ at Age 7 Years.” https://doi.org/10.3390/ijerph14050506.
- Criswell, Rachel, Kelsey Gleason, Ahlam K Abuawad, Margaret R Karagas, Kathleen Grene, Ana M Mora, Brenda Eskenazi, et al. 2026. “HHS Public Access.” Pediatr Clin North America 72 (1): 65–83. https://doi.org/10.1016/j.pcl.2024.07.030.A.
- Liu, Qi, Xinchen Shu, Jiaxin Cao, Yixin Wang, Yuxin Liu, Feng Jiang, and Jin Shu. 2026. “Global Trends in Research on Environmental Chemical Exposure and Childhood Learning Disabilities : Insights from a Two ‑ Decade Bibliometric and Latent Dirichlet Allocation Analysis.”
- MF Bouchard, DC Bellinger, RO Wright, and MG Weisskopf. 2013. “NIH Public Access.” Pediatrics 125 (6). https://doi.org/10.1542/peds.2009-3058.ATTENTION.
- Shelton, Janie F., Estella M. Geraghty, Daniel J. Tancredi, Lora D. Delwiche, Rebecca J. Schmidt, Beate Ritz, Robin L. Hansen, and Irva Hertz-Picciotto. 2015. “Neurodevelopmental Disorders and Prenatal Residential Proximity to Agricultural Pesticides: The CHARGE Study.” Everyday Environmental Toxins: Childrens Exposure Risks 122 (10): 183–200. https://doi.org/10.1201/b18221.
