From the Guidelines
Prenatal exposure to organophosphate pesticides is likely detrimental to brain function and increases the risk of autism spectrum disorder (ASD) in children, as evidenced by multiple epidemiologic studies and experimental animal studies 1.
Environmental Factors and Autism Risk
Environmental factors, including exposure to certain chemicals and pollutants, play a significant role in autism development alongside genetic predisposition. Research indicates that prenatal and early childhood exposures to these factors can influence autism risk.
- Advanced parental age
- Maternal infections during pregnancy
- Exposure to air pollution
- Pesticides, such as organophosphate pesticides
- Certain medications like valproic acid during pregnancy
- Maternal health conditions, including diabetes, obesity, and immune system disorders
- Premature birth and low birth weight are associated with higher autism risk
Organophosphate Pesticides and Autism
The weight of evidence clearly indicates that OP exposures during prenatal development are likely detrimental to brain function, with outcomes associated with OP pesticide exposure to the fetus including abnormal primitive reflexes in newborns, mental and motor delays among preschoolers, and decreases in working and visual memory, processing speed, verbal comprehension, perceptual reasoning, and IQ among elementary school–age children 1.
- A higher likelihood of an ASD diagnosis was observed for children born to women residing within (versus beyond) 1.5 km of OP pesticide applications on agricultural fields; the strongest associations were for chlorpyrifos 1.
- Higher OP pesticide metabolite concentrations in maternal urine during pregnancy were associated with ASD traits identified in adolescence 1.
Conclusion Not Needed, Recommendation Based on Evidence
Based on the strongest and most recent evidence, it is recommended that pregnant women avoid exposure to organophosphate pesticides to reduce the risk of autism spectrum disorder (ASD) in their children 1.
- This can be achieved by avoiding residential areas near agricultural fields where OP pesticides are applied and reducing exposure to these chemicals in the home and workplace.
- Further research is needed to fully understand the relationship between environmental factors and autism risk, but the current evidence suggests that reducing exposure to harmful chemicals and pollutants is crucial for preventing autism and promoting healthy brain development.
From the Research
Environmental Factors and Autism Spectrum Disorders
- The relationship between environmental factors and autism spectrum disorders (ASD) has been studied extensively, with research suggesting that exposure to certain environmental pollutants may contribute to the development of ASD 2, 3, 4.
- Studies have identified several environmental toxicants that may be associated with ASD, including heavy metals (such as mercury and lead), persistent organic pollutants (such as DDT and PCBs), and emerging chemicals of concern (such as phthalates and BPA) 2, 3.
- A systematic review and meta-analysis of cohort studies found significant associations between exposure to certain environmental pollutants, including nitrogen dioxide, copper, mono-3-carboxy propyl phthalate, monobutyl phthalate, and polychlorinated biphenyl (PCB) 138, and the development of ASD 4.
- Another study found that traffic-related air pollutants, some metals, and several pesticides were associated with ASD, although the results were not conclusive 3.
Nutritional Factors and Autism Spectrum Disorders
- Research has also explored the potential relationship between nutritional factors, such as omega-3 fatty acid supplementation, and ASD 5, 6.
- A systematic review found that omega-3 fatty acid supplementation had no significant effect on core symptoms of ASD, although vitamin D supplementation may have a positive effect on behavioral functioning in individuals with ASD 6.
- Another study found that omega-3 fatty acid supplementation had no significant effect on social interaction, communication, or stereotypy in individuals with ASD 5.
Limitations and Future Directions
- Despite the growing body of research on environmental and nutritional factors and ASD, more studies are needed to fully understand the relationships between these factors and the development of ASD 2, 3, 4.
- Future research should aim to address the limitations of current studies, including the need for more accurate exposure measurement and larger sample sizes 3, 4.