Pollutant Burden in Autism Spectrum Disorder: Mechanistic Convergence, Genetic Susceptibility, and Clinical Translation

Abstract

Highlights What are the main findings? Six major classes of environmental pollutants—micro/nanoplastics, plastic-associated endocrine-disrupting chemicals, ambient/indoor air pollution, tire wear particles, heavy metals and pesticides, and industrial chemicals/POPs—converge on a shared set of mechanisms (oxidative stress, neuroinflammation, endocrine disruption, and impaired microglial synaptic pruning) that plausibly contribute to ASD risk, largely through the oxidative stress/inflammation pathway of our two-path model. Ultra-processed food intake is reviewed alongside them as a parallel, non-pollutant contributor to the same inflammatory pathway, not as a seventh pollutant class. Human evidence for micro/nanoplastics has moved beyond simple detection to include placental genotoxicity, direct oxidative stress effects in human placental tissue, and fetal endocrine correlates, complementing an extensive rodent literature that directly links prenatal/early-life exposure to ASD-relevant social and repetitive behavior deficits. Exposure timing relative to specific developmental windows, rather than cumulative dose alone, appears to determine which process is disrupted. What are the implications of the main findings? Genetic variation in folate pathway and mitochondrial genes, as well as individual differences in folate/ vitamin B sufficiency, are proposed as a candidate effect modifier rather than an established protective factor to modify susceptibility to pollutant-driven oxidative stress across the six pollutant classes. This remains a testable gene-by-pollutant research priority, not yet a validated finding. Because several of these exposures are ubiquitous and largely unregulated, meaningful risk reduction likely requires population-level policy action (e.g., additive restrictions, expanded biomonitoring, air quality standards) alongside individual-level, low-risk strategies such as dietary pattern and household exposure reduction, rather than relying on individual behavior change alone. Abstract Autism spectrum disorder (ASD) risk reflects genetic susceptibility and modifiable environmental exposures acting during fetal and early postnatal critical periods. Building on our prior two-path model, in which folate receptor autoantibody-driven cerebral folate deficiency and oxidative stress/neuroinflammation converge on disrupted neurodevelopment, this review provides the first full mechanistic treatment of environmental pollutants within that framework. We synthesize evidence across seven exposure categories: micro/nanoplastics, plastic-associated endocrine-disrupting chemicals, ambient/indoor air pollution, tire wear particles and 6PPD-quinone, heavy metals and pesticides, industrial chemicals and persistent organic pollutants, and ultra-processed food intake as a parallel, non-pollutant contributor to the same inflammatory pathway. Human biomonitoring of micro/nanoplastics has progressed beyond detection in the placenta, brain and breast milk to direct evidence of placental genotoxicity and fetal endocrine disruption, complementing rodent data linking early-life exposure to impaired corticogenesis, disrupted microglial synaptic pruning, and ASD-relevant behavioral deficits. Across categories, oxidative stress, barrier disruption, neuroinflammation, endocrine disruption, and epigenetic modification recur as convergent mechanisms acting on trimester- and age-specific windows of vulnerability. Genetic variation in folate pathway and mitochondrial genes, as well as folate/vitamin B sufficiency, are proposed as candidate effect modifiers rather than established protective factors to modify susceptibility to this pollutant burden. Most evidence is associational or mechanistic rather than trial-based; we grade evidence strength and translate findings into biomarker-guided clinical and population-level policy guidance.