title: Environment and Autism: Current State of the Science.
abstract: Research into environmental risk factors for autism has grown dramatically over the past 10 years, providing evidence that non-genetic factors acting during the prenatal period may influence the underlying neurodevelopmental processes. This paper reviews the evidence on modifiable preconception and/or prenatal factors that have been associated with autism spectrum disorder (ASD), including only human studies with at least 50 cases of ASD, having a valid comparison group, conducted within the past decade, and focusing on maternal lifestyle or environmental chemicals. Consistent results have been reported for an association of higher maternal intake of certain nutrients and supplements with reduction in ASD risk, with the strongest evidence for folic acid supplements. A number of studies have demonstrated significant increases in ASD risk with estimated exposure to air pollution during the prenatal period, particularly for heavy metals and particulate matter. A few studies suggest a link with organophosphate pesticides. More rigorous ascertainment of exposure is needed for studies of substance use; most investigations adjusting for potential confounders, but relying on self-reported use, have shown no links between maternal smoking or alcohol consumption and ASD. Little research has assessed other persistent and non-persistent organic chemical pollutants, such as are found in common household or personal care products, in association with ASD specifically. More work is needed to examine fats, vitamins, and other maternal nutrients, as well as endocrine-disrupting chemicals and pesticides, in association with ASD, given sound biological plausibility and evidence regarding other neurodevelopmental outcomes. In addition, the field could be advanced by the use of large-scale epidemiologic studies, attention to critical etiologic windows and how these vary by exposure, interactions with genetic susceptibility, and a focus on underlying mechanisms.
authors.affiliation: Assistant Professor, Department of Public Health Sciences and UC Davis MIND Institute; Scholar, Building Interdisciplinary Research Careers in Women's Health (BIRCWH), School of Medicine.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Schmidt
authors.affiliation: Postdoctoral research fellow in the Autism Research Training Program of the MIND Institute of UC Davis.
authors.forename: Kristen
authors.initials: K
authors.lastname: Lyall
authors.affiliation: Professor and Chief, Division of Environmental and Occupational Health, Department of Public Health Sciences, School of Medicine and the UC Davis MIND Institute; Director, Northern California Collaborative Center for the National Children's Study; Deputy Director, UC Davis Children's Center for Environmental Health; Principal Investigator, The CHARGE Study and The MARBLES Study.
authors.forename: Irva
authors.initials: I
authors.lastname: Hertz-Picciotto
keywords: air pollution; autism; endocrine disruptors; environment; lifestyle; nutrition; pesticides; tobacco smoke