Autism is a neurodevelopmental disorder characterized by impaired social interaction as well as verbal and non-verbal communication. This condition is commonly referred to as “autism spectrum disorders” (ASD) which include autism, Asperger’s syndrome, pervasive developmental disorders not otherwise specified (PDD-NOS) and high-functioning autism. According to the statistics data gathered in 2002 there are more than 550,000 children affected by varying degrees of autism spectrum disorders (ASD). It has also been reported that autism is the fastest growing developmental disability, increasing at a rate of 10 to 17 percent annually according to the Autism Society of America. It is becoming increasingly apparent that environmental neurotoxins in combination with genetic predispositions could also create adverse gene-environment interactions.
Surveys conducted in California indicates a 210% increase in the number of cases of autism in children over the past 10 years. There is increasing concern that certain chemicals (such as mercury, halogenated aromatics and pesticides) and biotic factors (such as vaccine antigens) may act synergistically to alter certain susceptibility or genetic risk factors to result in ASD. The UC Davis researchers at the Children’s center have suggested an association between thimerosal (ethyl mercury) and immune system dysfunction in mice. A key point highlighted in the study was the fact that even though moderate amounts of chemicals, such as lead and mercury, were needed to cause neurological damage in most adults, only small amounts might be needed to damage the developing brains in babies, infants and young children. Based on the data from the study, it was suggested that living in areas with higher ambient levels of HAPs, especially metals and chlorinated solvents, during pregnancy or early childhood could be associated with a moderately increased risk of autism. This study highlighted the need for more complex etiologic studies combining exposure to multiple compounds by various pathways with genetic information to further understand the contribution of environmental exposures to the development of autism.
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