Increased awareness and changes in diagnostic criteria can’t entirely explain the massive increase in autism — the U.S. Centers for Disease Control reported a 57% increase between 2002 and 2006. Another factor may involve environmental pollutants.
A Californian study involving 304 autism cases and 259 typically developing controls has found that living within 309 meters of a freeway at birth or during the third trimester was associated with a two-fold increase in autism risk. This association held after adjustment for gender, ethnicity, parental education, maternal age, or prenatal smoking. The researchers found no consistent pattern of association of autism with proximity to a major road.
The finding is consistent with other evidence that oxidative stress and inflammation are involved in the pathogenesis of autism. This is likely to be only one of many environmental factors that are involved.
(2010). Residential Proximity to Freeways and Autism in the CHARGE study.
Environmental Health Perspectives.