Pesticides and Autism: What the Research Shows
Autism spectrum disorder is a diverse group of conditions marked by difficulty with social interaction and communication. Pesticides are not an established cause, though studies link organophosphates, pyrethroids, organochlorines, glyphosate and neonicotinoids to autism. The CHARGE study found a 60% higher risk when mothers lived near organophosphate applications. Pregnancy is when exposure matters most, mainly through food, with spray drift and home use adding to it. Pesticides might affect the developing brain through neuroexcitability, oxidative stress and immune function. Pregnant women can reduce exposure by reading the product label first. The EPA revoked all chlorpyrifos tolerances in 2021, a step a court later reversed. Other factors also raise risk, including air pollution, metals and antiseizure medicines.
What Is Autism Spectrum Disorder?
Autism spectrum disorder is a diverse group of conditions marked by some degree of difficulty with social interaction and communication. Autism spectrum disorder shows symptoms that are typically recognizable in the first two years of life. Diagnosis often comes much later. The World Health Organization gave this definition in 2025.
About 1 in 31 (3.2%) 8-year-old children in 16 US surveillance areas had autism spectrum disorder in 2022. The National Institute of Mental Health reported this figure in 2025. The Centers for Disease Control and Prevention funds the ADDM Network, a group of programs that estimate these numbers.
Autism spectrum disorder is 3.4 times as prevalent among boys (4.9%) as among girls (1.4%).
About 1 in 127 persons worldwide had autism in 2021. Jinan Zeidan reviewed 99 estimates from 71 studies in 2022. The review found a median global prevalence of 100 per 10,000 persons. A median of 33.0% of autism cases have co-occurring intellectual disability.
Do Pesticides Cause Autism?
No. Pesticides are not an established cause of autism. Pesticides are among exposures that may be associated with increased risk in the CHARGE study. Both genetic and environmental factors likely play a role in autism.
The MARBLES study follows more than 400 mother-child pairs. It collects information on exposures before, during and after pregnancy that may contribute to autism.
A 2022 meta-analysis of maternal exposure to pesticides and the risk of autism spectrum disorders in offspring pooled 50,426 participants. It included 5810 participants with autism. The analysis of 12 autism studies found a positive pooled association with maternal pesticide exposure, with publication bias possible. The pooled odds of autism in offspring rose with maternal pesticide exposure, a positive but modest association. Pooled associations depend on how exposure is measured, whether by residential proximity, self-report or biomarkers.
A 2012 report on gestational pesticide exposure found that conclusive replicated findings have yet to appear on any specific exposure. Little is known about the timing or dose, or which mechanism is sufficient to induce autism. A 2013 report found that epidemiologic studies as a whole did not strongly implicate any particular pesticide as causal.
Why Do Studies on Pesticides and Autism Disagree?
Studies on pesticides and autism disagree because small studies measure exposure in inconsistent ways and each design has limits. Small studies of prenatal organophosphate exposure have yielded inconsistent findings, with some finding a connection and others not. Haleigh M Cavalier reached the same conclusion in 2026: evidence linking prenatal organophosphate exposure to autism remains inconsistent.
The CHARGE study assessed pesticide applications within 1.75 km of each mother’s residence from 3 months before conception through delivery. The study relied on retrospective data collection, and no biological samples were collected during gestation. CHARGE has enrolled more than 1,800 children and seeks to clarify the roles of genetics and exposures in autism.
Sharon K Sagiv found in 2018 that urinary metabolites were linked to social behavior traits in one California cohort. Residential proximity to organophosphate use was not linked to those traits.
A 2023 report on 27 observational studies named exposure assessment, small sample sizes and chemical mixtures as limits. In most animal studies, effects appeared at dose levels of the same order of magnitude or higher. The comparison point is the US chronic risk point of departure.
Do Urine Biomarker Studies Find a Link Between Pesticides and Autism?
It depends. The ECHO cohort found no significant link between urine biomarkers of pesticides and autism-related traits. A French cohort linked chlorpyrifos metabolites to higher autistic trait scores.
Among 3339 mother-child pairs from 20 sites, the ECHO cohort measured urinary 3,5,6-trichloro-2-pyridinol and six dialkyl phosphate metabolites. Haleigh M Cavalier led this analysis in 2026. Children were assessed at 5 to 7 years on average with the 65-item Social Responsiveness Scale. Among the mothers, 99 percent had detectable organophosphate metabolites in urine.
Dialkyl phosphate metabolites in urine serve as markers of organophosphate exposure during pregnancy.
Mathilde Lizé of Université Rennes 1 studied the French PELAGIE cohort in 2022. Urine was collected before 19 weeks of gestation. Chlorpyrifos exposure was associated with higher autistic trait scores, with a stronger estimate among boys.
A 2023 pooled analysis of 27 studies found no association across chemicals, including organophosphates. Its authors warned that this is not definitive evidence of absence.
Which Pesticides Are Linked to Autism?
Pesticides linked to autism include organophosphates, pyrethroids, organochlorines, glyphosate and neonicotinoids. Jeanne Sandrine Ongono found in 2020 that early exposure to organophosphates, organochlorines, pyrethroids or carbamates was associated with autism. Key types include:
- Organophosphates: Organophosphates are insecticides that inhibit acetylcholinesterase and include chlorpyrifos, diazinon and malathion. Prenatal exposure to these agents brought small to moderately increased risks in the Central Valley of California.
- Pyrethroids: Pyrethroids are insecticides that include permethrin and bifenthrin. They may activate microglial cells through voltage-gated sodium channels, and their association with autism is stronger than for organochlorines.
- Organochlorines: Organochlorines are persistent insecticides, and their association with autism is less evident than for organophosphates and pyrethroids. Maternal p,p’-DDE levels were linked to autism in offspring in 778 matched case-control pairs.
- Glyphosate: Glyphosate is a widely used herbicide with a moderate level of evidence in children and a high level in rodents. Its prenatal exposure was associated with higher odds of autism in the Central Valley.
- Neonicotinoids: Neonicotinoids are newer insecticides, and the level of evidence for imidacloprid in children is inadequate. Evidence for newer groups stays thin.
A 2021 systematic review covered 45 human studies and 16 preclinical studies. It concluded that gestational exposure to certain organophosphates could be linked to clinical signs of autism. Data for other pesticides and ages remain inconclusive.
Prenatal odds of autism for six pesticides stayed modest in the Central Valley study, which covered 2961 autism cases.
Is Chlorpyrifos Linked to Autism?
Yes. Chlorpyrifos is linked to autism in several human studies, but causation is unresolved. Second-trimester chlorpyrifos applications near the home gave higher odds of autism, among the strongest associations in CHARGE. Janie F Shelton reported this CHARGE finding in 2014.
Chlorpyrifos or its metabolites in urine were linked to autistic traits, reported Mathilde Lizé in 2022.
Mice exposed prenatally to chlorpyrifos at 5.0 mg/kg showed reduced social preference in adulthood. At 2.5 mg/kg they showed enhanced restricted interest, a 2017 report found. A 2022 study found social alterations only in prenatally treated male mice.
EPA concluded that the science on chlorpyrifos and neurodevelopmental effects remained unresolved. In March 2017, EPA denied the 2007 petition requesting revocation of all pesticide tolerances for chlorpyrifos.
Is Glyphosate Linked to Autism?
Yes. Glyphosate is linked to autism in one large registry study and a systematic review, but causation is not established. A 2020 review by Jeanne Sandrine Ongono rated glyphosate evidence as moderate in children and high in rodents.
Ondine S von Ehrenstein described the Central Valley finding in 2019. Prenatal exposure to glyphosate was associated with higher odds of autism in the Central Valley. The risks were small to moderately increased within 2000 m of the mother’s residence. Glyphosate showed the highest odds of the six pesticides, though the ratio stayed moderate. Cases of autism with intellectual disability had higher glyphosate odds, and the ratio rose further.
Glyphosate is the most commonly used pesticide worldwide, with exposure through occupation and food residue. A 2025 scoping review by Bryan Gonzalez found animal and human survey correlations between glyphosate-based herbicide exposure and autism. Additional research is needed to separate prenatal from postnatal exposure.
Glyphosate-based herbicide exposure before and after birth leads to neuronal damage through glutamate excitotoxicity in animal studies. Xiu He reviewed glyphosate, chlorpyrifos, pyrethroids and avermectins in 2022. Targets included acetylcholinesterase inhibition, gut microbiota and glial cells.
How Much Does Pesticide Exposure Raise Autism Risk?
Pesticide exposure raised autism risk by 60% in the CHARGE study when mothers lived near organophosphate applications. Infant exposure in the first year raised odds for autism with intellectual disability by up to 50% for some pesticides. Janie F Shelton of the University of California led the CHARGE analysis in 2014.
About one-third of CHARGE mothers lived within 1.5 km (just under 1 mile) of an agricultural pesticide application. The CHARGE analysis compared 486 autism cases with 316 controls.
In the Spanish case-control study, autism prevalence was higher in regions with elevated pesticide use than in low-use regions. Single-pesticide odds were small, regional high-use odds were larger, and proximity to organophosphates gave a 60% increased risk.
A 2019 study by Ondine S von Ehrenstein reported the 50% figure for infants in the Central Valley. Effects are reported as odds from case-control designs, which compare cases with controls.
When Does Pesticide Exposure Matter Most for Autism Risk?
Pregnancy is the time when pesticide exposure matters most for autism risk. Pesticide exposure in pregnancy seems to have the greatest impact on the onset of autism in children.
Certain pesticides such as organophosphates pass through the placental barrier and can directly affect fetal neurodevelopment. Third-trimester organophosphate proximity and pyrethroid exposure just before conception or in the third trimester were linked to autism. During pregnancy the baby’s brain, nervous system and organs develop rapidly and are more sensitive to pesticide toxicity. The prenatal period and childhood are critical times for brain development.
The Columbia University Mailman School of Public Health reported in 2025 that prenatal pesticide exposure harms babies in the womb. Exposure in the first year of life remains relevant, as the 50% rise in odds noted earlier shows.
How Might Pesticides Affect the Developing Brain?
Pesticides might affect the developing brain through neuroexcitability, oxidative stress and immune function. These are shared mechanisms between autism and pesticide effects. Organophosphates inhibit acetylcholinesterase, an enzyme that breaks down neurotransmitters at the post-synaptic membrane.
In humans, acetylcholinesterase is a cholinergic enzyme that hydrolyzes acetylcholine into choline and acetate. Neurodevelopmental dysfunction occurs at subacute levels when acetylcholinesterase inhibition is absent.
Pyrethroids and organochlorines reach nerve cells through sodium channels. Organochlorines persistently open sodium channels and interact with GABA receptors. Pyrethroids may activate microglia through voltage-gated sodium channels.
Chlorpyrifos in mice may act through the hormones oxytocin and vasopressin, which affect social behavior. Prenatal chlorpyrifos in mice reduced social preference and increased restricted interest in adulthood. Males were more sensitive, which matches the male bias in autism.
Sara Mostafalou listed cholinergic deficit, oxidative stress, neuro-inflammation and epigenetic modifications as mechanisms of organophosphorus pesticides in 2018. A 2022 narrative review by Xiu He named neural dendrite morphology, synaptic function and glial cells as developmental targets.
Paraoxonase 1 (PON1) forms with less activity were linked to autism in Caucasian families in North America. They were not linked to autism in Italian families.
Who Is Most at Risk From Pesticide Exposure and Autism?
Children of mothers who lived near treated agricultural fields during pregnancy carry the most pesticide exposure risk linked to autism. Boys and infants exposed in the first year of life form the other groups most at risk of autism.
Pregnant women near fields where pesticides were applied are the group in the strongest proximity analyses. A 2018 study by Sharon K Sagiv examined a population living in proximity to agriculture. Males had higher odds of autism than females in southern Spain, where the study covered 2821 people with autism.
Farmworkers, as agricultural workers, may suffer some of the greatest exposure risks from pesticides. Male gender ranked among the factors associated with autism risk in a 2017 meta-analysis of 17 studies. Boys carry the higher baseline prevalence noted earlier. Maternal age of 35 years or older gave higher pooled odds of autism. The odds were higher for autism with intellectual disability. Chlorpyrifos exposure carried a stronger estimate among boys, as urine biomarker work showed.
How Does Pesticide Exposure Happen During Pregnancy?
Pesticide exposure happens during pregnancy mainly through food, with spray drift and home use adding to it. Outside agricultural or occupational settings, most Americans primarily encounter organophosphate insecticides when they eat fresh produce.
The primary route of human chlorpyrifos exposure is ingestion of foods containing residues. Agricultural communities face dermal contact and inhalation. Indoor use of chlorpyrifos was phased out in the US in 2005.
Michiel A van den Dries studied 784 pregnant women in Rotterdam in 2018. Each 100 g/d difference in fruit consumption was associated with a 7% higher DAP metabolite concentration. The median DAP metabolite concentration was 311 nanomoles per gram creatinine in the first trimester.
Spray drift carries pesticides beyond buffer zones around the point of application and into homes and workplaces. In 2012, EPA lowered aerial pesticide application rates and created no-spray buffer zones around schools, homes and other sensitive areas. The 2015 Agricultural Worker Protection Standard reduces the risk of pesticide poisoning and injury among agricultural workers and pesticide handlers.
Amanda J Goodrich reported in 2025 that professionally applied indoor insecticides during pregnancy were associated with higher odds of autism. The study included 1526 participants.
How Can Pregnant Women Reduce Pesticide Exposure?
To reduce pesticide exposure, pregnant women should start by reading the product label. Choose the least toxic option or an Integrated Pest Management method. Have someone else apply the pesticide and leave the area. Allow plenty of time for the home to air out and the pesticide to dry before returning. The National Pesticide Information Center gave this advice in 2025.
Integrated Pest Management combines methods to prevent and eliminate pests in the most effective and least hazardous manner. It applies to the home, garden and workplace, EPA notes.
Washing and scrubbing fresh produce helps remove traces of chemicals, and people should keep eating a variety of foods.
Urinary 3-phenoxybenzoic acid measured 0.95 versus 0.27 micrograms per liter in conventional versus organic produce groups. This 24-week trial enrolled 20 pregnant women in 2019. Carly Hyland reported in 2019 that an organic diet cut urinary TCPy by 60.7% in 16 participants.
What Has the EPA Done About Chlorpyrifos?
What the EPA has done about chlorpyrifos is revoke all tolerances in 2021, a step a court later reversed. The final tolerance rule of August 18, 2021 revoked all chlorpyrifos tolerances. EPA found that aggregate exposures did not meet the legally required safety standard.
Chlorpyrifos has been used as a pesticide since 1965. In 2000, registrants voluntarily agreed with EPA to eliminate, phase out and modify certain uses. On November 2, 2023, the Eighth Circuit vacated the final rule. The tolerances were reinstated on December 28, 2023.
Product labels now require handlers of chlorpyrifos to wear chemical resistant gloves, coveralls and respirators. The European Union, Canada and several US states have restricted chlorpyrifos on food.
The Federal Insecticide, Fungicide, and Rodenticide Act governs registration. EPA registers a pesticide only if it finds no unreasonable adverse effects on humans or the environment. A 2007 petition from the Pesticide Action Network North America and the Natural Resources Defense Council prompted the rule.
Stine Søgaard Normann studied 812 mother-child pairs in 2024. Maternal TCPy at mid-level exposure was significantly associated with child IQ at 7 years. Jianqiu Guo studied 377 mother-child pairs in 2019 and found no significant link with children’s neurodevelopment.
What Other Factors Raise the Risk of Autism?
Other factors that raise the risk of autism include parental and birth factors, air pollution and metals, and antiseizure medicines. More research is needed to understand each factor and how it interacts with genetic variations. Key types include:
- Advanced parental age: Advanced parental age means a mother or father aged 35 years or older. It was linked to higher autism risk in a meta-analysis of 17 studies.
- Maternal diabetes and hypertension in pregnancy: Maternal diabetes during pregnancy occurs more frequently in children with autism. Gestational hypertension and gestational diabetes were pooled among the risk factors in the same analysis.
- Preterm birth and low birth weight: Preterm birth is gestational age of 36 weeks or less. Low birth weight and severe birth complications occur more frequently in children with autism.
- Prenatal air pollution and heavy metals: Prenatal exposure to air pollutants or certain heavy metals occurs more frequently in children with autism. Air pollution may play a role in autism.
- Prenatal valproate and carbamazepine: These are medicines used for seizures. Maternal use of valproate during pregnancy was associated with a significantly increased risk of autism, even after adjusting for maternal epilepsy.
A 2017 meta-analysis of prenatal, perinatal and postnatal factors associated with autism pooled 17 studies. It covered 37,634 autistic children and 12,081,416 nonautistic children.
Mothers who took folic acid in the first month of pregnancy had a lower risk of a child with autism.
