Considering Toxic Chemicals in the Etiology of Autism
"A large body of evidence, including decades of research on lead and child IQ, indicate a link between toxic environmental exposures and poorer neurodevelopmental outcomes.5 In animal models and human studies, several toxic chemicals have been implicated in ASD and ASD-related traits and biological markers.2 Specifically, scientists have found that air pollution exposures during pregnancy and early infancy, at levels typically found in large cities, are associated with autism.6–8 Several studies suggest that gestational exposures to some neurotoxic and endocrine-disrupting pesticides, including organochlorines, organophosphates, and pyrethroids, increase the chances of an autism diagnosis or autism-related behaviors in children.9 Evidence is emerging that other toxic chemicals are associated with autism or autism-related behaviors, notably phthalates, ubiquitous chemicals that cause a decrease in testosterone.10
Some environmental factors may also reduce the probability of autism. For example, folate, a vitamin involved in the manufacture and methylation of DNA, plays a critical role in neurodevelopment. Folic acid supplementation, at appropriate levels, around the time of conception appears protective for autism and may ameliorate the impact of toxic chemicals.11,12 In several studies, researchers have found that the associations linking autism with air pollutants, pesticides, and phthalates are stronger among children of women who either did not take folic acid or had higher folate requirements during pregnancy."