Environment may explain half of autism

A synthesis of systematic reviews finds that environmental factors could account for a large share of autism liability (authors cite up to ~40–50% of variance) and that specific risks include advanced parental age, birth complications involving hypoxia, certain heavy‑metal exposures, and nutritional deficiencies such as vitamin D. The review also rules out several widely discussed but unsupported causes (for example, vaccinations) and highlights major methodological gaps in existing studies. — If environmental causes explain a large fraction of autism risk, public policy should shift more funding and regulation toward prenatal care, pollution control, and prospective exposure studies rather than repeating debunked narratives.