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Part 1:

Environmental triggers are a neglected component of autism research

There is no doubt that an environmental factor has contributed to the dramatic increase in the incidence of autism over the past 15 years. Genetic factors are a component in the condition—concurrent rates of autism in identical twins approach 90 percent—but rates of inherited genetic diseases do not change abruptly in one generation, whereas autism rates skyrocketed during the 1990s. Rates of autism in the United States increased from fewer than 6 cases per 10,000 children in the 1980s to more than 60 per 10,000 children today (Blaxill 2004a). The American Academy of Pediatrics and the Centers for Disease Control (CDC) currently estimate that autism affects one in every 166 children (AAP 2004). Improved diagnosis does not adequately account for this increase (Blaxill 2004a, Croen 2003).

Autism is a complex neurological disorder characterized by severely impaired social interaction and language skills. The social and economic costs of the autism epidemic are staggering. In 2003, the Autism Society of America estimated the cost of treating the 1.5 million cases of autism to be $90 billion per year rising to $200-400 billion by 2010 (ASA 2003). In addition to the economic costs of treatment, autism is a tremendous burden to family members who must provide lifelong care to loved ones affected by the disorder.

There has been little progress in identifying pre- and post-natal environmental exposures that might trigger the severe impacts to brain development, intestinal and immune dysregulation that characterize autism disorders (London 2000). Hundreds of studies have explored the genetic roots of the autism epidemic, but none has uncovered a single gene or vulnerability to account for more than a fraction of cases.

Children's exposure to mercury in immunizations has been a long-standing concern of autism advocates—and for good reason. Mercury is highly toxic to brain cells and other body systems impacted by autism. Several classic features of autism—speech loss and loss of social and communication skills—are signature traits of mercury poisoning. Many parents report children slipping into autism shortly after receiving multiple mercury-containing vaccinations.

One in every six children born in the United States, or 630,000 per year, are exposed to potentially unsafe levels of mercury during pregnancy from contaminated seafood in the maternal diet, creating a background level of exposure that could be exacerbated by cumulative and frequent mercury doses from vaccinations (Mahaffey 2004). Virtually all children in the U.S. were vaccinated repeatedly with mercury-containing vaccine during the 1990s; if a percentage of these children had a metabolic imbalance that increased their vulnerability to mercury, this near universal exposure could help explain the dramatic nationwide increase in autism that followed directly on the heels of this abrupt rise in thimerosal use. The findings discussed here, that autistic children share a common deficit in antioxidant protection, call into question the conclusion that mercury in vaccines is uniformly safe for all children, and underscores the need for a broader look at the role of environmental chemicals in the autism epidemic.

Every existing study that has failed to find a link between thimerosal exposure and autism has looked at disease rates in vaccinated children without regard to their individual metabolism. To properly investigate the role of mercury-containing shots in a vulnerable group, researchers would have to compare autism rates in children with the same type of vulnerability. This has not been done.

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