Chlorpyrifos and other organophosphate insecticides had no association with autism at low exposure levels, according to data recently published in JAMA Paediatrics by US scientists.
MedPage Today reports that relatively low levels of prenatal exposure to organophosphate pesticides showed no relationship with social communication problems and other traits related to autism in children, the prospective ECHO study showed.
The study had assessed maternal values of six dialkyl phosphate (DAP) metabolites and 3,5,6-trichloro-2-pyridinol (TCPy), a specific metabolite resulting from chlorpyrifos breakdown.
Neither was linked with parent-reported autism-related traits (β per doubling of TCPy concentration = -0.13, 95% CI -0.57 to 0.31; β per doubling of DAP = -0.42, 95% CI -1.03 to 0.19), reported Haleigh Cavalier, PhD, MPH, of NYU Langone Health in New York City, and co-authors.
Results were consistent after adjusting for dietary confounders, in different models and sensitivity analyses, and for both boys and girls, the researchers wrote in JAMA.
Earlier research suggested that organophosphate pesticides raised children’s risk for neurodevelopmental issues like IQ loss and attention deficit-hyperactivity disorder (ADHD), they noted.
“This study adds another piece to a large and complex puzzle, bringing us closer to understanding how environmental exposures shape neurodevelopment,” Cavalier told MedPage Today.
“While the findings suggest that organophosphate pesticides were not a major driver of autism-related traits at the exposure levels observed in our study, that should not be taken to mean these chemicals are safe,” she said. “Rather, the results inform future work that should focus on chemical mixtures and other factors that may influence risk, such as genetic susceptibility or high-exposure occupations.”
Organophosphate pesticides are widely used in agriculture, and their metabolites are frequently detected in US population samples. Diet, including pesticide residues in fruits and vegetables, is the way most people are exposed to them.
“Conventional produce consumption is one of the strongest predictors of organophosphate pesticide biomarker concentrations, and organophosphate metabolites decrease substantially after adoption of an organic diet,” Cavalier and co-authors observed.
Chlorpyrifos is an organophosphate insecticide used on soybeans, fruit and nut trees, broccoli, cauliflower, and other row crops.
In 2021, the Environmental Protection Agency (EPA) revoked all tolerances for the chemical but in 2023, the US Court of Appeals for the Eighth Circuit overturned the EPA’s ban. In 2026, the EPA issued a technical correction to reflect the Eighth Circuit’s decision.
The European Union banned chlorpyrifos sales in 2020 after its food safety authority said there was no safe exposure level. In a 2025 study, high prenatal exposure to chlorpyrifos for pest control in residential settings (a use now banned in the US) was associated with brain abnormalities in children.
A meta-analysis suggested high prenatal organophosphate pesticide exposure may be a risk factor for autism, Cavalier and colleagues noted. The CHARGE study of residential proximity to agricultural pesticides and the CHAMACOS study in Salinas Valley reported links between prenatal exposure and neurodevelopment.
Researchers in The Netherlands did not find a relationship with autistic traits or ADHD, however. An Ohio-based study also showed no link between exposure and autistic behaviour.
“Differences between study populations are likely to reflect variations in exposure levels, timing, and sources; the presence of agricultural co-exposures; and differences in population characteristics or underlying risk factor distributions,” Cavalier and co-authors pointed out.
“Our results therefore contribute to an emerging pattern: positive associations tend to appear where exposures are high and associated with an agricultural context, whereas null associations are more common in general population settings characterised by low exposure occurring primarily through diet.”
The researchers leveraged data from the observational ECHO cohort to study 3 339 mother-child pairs in the US. Prenatal exposure was measured by concentrations of TCPy and the sum of six DAP metabolites – three dimethyl phosphates and three diethyl phosphates – in mothers’ urine. Almost all mothers (99%) had detectable levels of organophosphate pesticides in their samples.
Autism-related outcomes were assessed when children were an average of 6.4 years old. Parents reported autism-related traits in children using the Social Responsiveness Scale (SRS), a measure that captures social communication and autistic traits.
‘In large cohorts, the SRS has demonstrated predictive validity for autism spectrum disorder diagnoses and functional and clinical outcomes later in childhood,” Cavalier and co-authors wrote.
The analysis used several models to estimate associations between metabolite markers and SRS scores overall and by child sex, adjusting for maternal socio-demographic and behavioural factors. Half of the children in the study were girls.
Urinary biomarkers were derived mainly from single urine samples and are subject to within-person variability, the researchers acknowledged. The metabolites measured in the study are short-lived, they noted.
“Given the known adverse impacts of pesticides in other contexts, further research should consider interactions with other factors, genetic susceptibility, higher exposures, or combined chemical mixtures,” they wrote.
Study details
Prenatal organophosphate exposure and autism-related traits in children
Haleigh Cavalier, Heather Volk, Apollo Kivumbi et al.
Published in JAMA Paediatrics on 24 August 2026
Abstract
Importance
Organophosphate pesticides (OPs) are established neurotoxicants; prenatal OP exposure is widespread in the US population, primarily through diet. Evidence linking prenatal OP exposure to autism spectrum disorder (ASD) and autism-related traits remains inconsistent.
Objective
To examine the association between prenatal OP exposure and autism-related traits in childhood and to assess potential differences in the association by child sex and maternal diet.
Design, Setting, and Participants
This pooled prospective cohort study used harmonised data from mother-child pairs from 20 study sites in the Environmental influences on Child Health Outcomes (ECHO) cohort. Participants were recruited from January 1997 through December 2019, and autism-related outcomes were assessed in children ages 2 to 19 years. Data analysis was performed from April 2024 and November 2025.
Exposure
Prenatal OP exposure using urinary concentrations of 3,5,6-trichloro-2-pyridinol (TCPy) and the sum of 6 dialkyl phosphate (ΣDAP) metabolites.
Main Outcomes and Measures
Parents reported autism-related traits in children using the Social Responsiveness Scale (SRS). Multivariable linear, quantile, and logistic regression models were used to estimate associations between biomarkers and SRS T scores overall and by child sex, adjusting for maternal socio-demographic and behavioural factors. We further adjusted for dietary factors in additional models and tested effect modification by maternal diet quality in exploratory analyses.
Results
Among 3 339 mother-child pairs examined, mean (SD) maternal age was 31 (6) years, 1665 children (49.9%) were female, and the SRS was administered at a mean (SD) age of 6.4 (3.87) years. Crude or minimally adjusted models suggested inverse associations between prenatal TCPy or ΣDAP levels and SRS scores, but these associations attenuated and lost statistical significance after full adjustment (β per doubling of TCPy concentration [ng/mL] = −0.13; 95% CI, −0.57 to 0.31; β per doubling of ΣDAP [nmol/L] = −0.42; 95% CI, −1.03 to 0.19). Results were consistent across sex-stratified models, secondary analyses using quantile and logistic regressions, various sensitivity analyses, and after adjustments for dietary confounders. There was no evidence of effect modification by diet quality.
Conclusions and Relevance
In this large, prospective cohort study among the ECHO cohort, prenatal OP exposure was not associated with autism-related traits in childhood. Given the known adverse impacts of pesticides in other contexts, further research should consider interactions with other factors, genetic susceptibility, higher exposures, or combined chemical mixtures.
See more from MedicalBrief archives:
Contact with pesticides while pregnant linked to autism
Pesticides damaging Western Cape children’s brains – SA-Swiss study
Common pesticide adds to ADHD risk
Child cancer risk tied to multiple pesticide exposure – US study