Environmental risk factors for autism spectrum disorder (ASD)

Background: Autism Spectrum Disorder (ASD) is a significant public health concern. The prevalence rate of this heterogeneous group of neurological conditions has more than doubled in the US during the last twenty years. The amount and cost of care needed to provide support and services for families impacted by ASD are increasing as well. Current research suggests that the etiology of ASD is not wholly genetic. The objective of this research is to investigate environmental contributors to the disease. Parental, prenatal, and obstetric factors and exposure to air pollutants during the prenatal period were examined for potential associations with ASD status.\ud Methods: Risk factors were extracted from the birth certificates of singleton cases (n=198) and controls (n=4,801) from the Case-Control Study of Personal and Environmental Risk Factors for Childhood Autism in Southwestern Pennsylvania. Cases and controls were born between 2005 and 2009. The 2005 National Air Toxics Assessment (NATA) and the Toxic Release Inventory (TRI) for 2004 – 2009 were used to estimate air pollutant exposure during pregnancy. Logistic regression models estimated the odds of being an ASD case in all investigations.\ud Results: Multivariable logistic regression modelling showed that increased maternal age, greater maternal education, gestational hypertension, cesarean delivery, and maternal infection were independent risk factors for ASD. In the analysis comparing higher quartiles of NATA exposure estimates of metal compounds to the lowest quartile of metal exposure at mother’s residence at the time of her child’s birth, arsenic, chromium, and lead were significantly associated with being an ASD case. However, an analysis of proximity to chromium emitting industrial sites, as reported in the TRI, uncovered no elevated or statistically significant association with ASD status.\ud Conclusions: Maternal and birth characteristics as well as exposure to metal compounds during the prenatal period were shown to have an association with ASD in this case-control study. This research adds to a growing body of literature suggesting that environmental risk factors contribute to the ASD burden. However, improved exposure assessment methods and a prospective study design would aid in establishing a causal association