Researchers compared 959 children from six San Francisco Bay area counties who were born in 1994. Out of these, 284 were diagnosed with autism-spectrum disorders. The study showed that children with autism were more likely to be born in areas with high levels of mercury, cadmium, nickel, trichloroethylene and vinyl chloride. Elemental mercury -- which is released into the air from coal-burning power plants, chlorine factories and gold mines -- appears to be particularly hazardous.
In their report, the study authors said their research suggests "living in areas with higher ambient levels of hazardous air pollutants -- particularly metals and chlorinated solvents -- during pregnancy or early childhood, may be associated with a moderately increased risk of autism. These findings illuminate the need for further scientific investigation, as they are biologically plausible but preliminary and require confirmation."
Mercury levels are increasing in many parts of the world, and over the past 10 years the number of children diagnosed with autism has increased as well. This leads many scientists to suspect there may be a connection between pollutants and the neurological disorder. However, the study's lead author Gayle Windham cautions that more definitive evidence is needed before scientists will have a clear understanding of the effect of environmental pollutants on autism.