Letter spotlight: Dan Burton

Questioning a mercury link to autism

December 30, 2002

Your editorial of Dec. 11 accurately pointed out the growing dispute over whether there is a relationship between childhood vaccines and autism spectrum disorders. What is not in dispute is that there has been a shocking surge in the number of autistic children in the last decade, and nobody knows why.

In 1990, Indiana schools had 116 requests for services for autistic children. Last year, there were nearly 3,800. A recent study in California showed that autism cases have tripled there. One in 10,000 children used to be affected by autism; now the National Institutes of Health estimates that one in 250 is. Nationwide, as many as 1.5 million Americans are believed to have some form of autism spectrum disorder. We have an epidemic on our hands and must not stop looking at any possible causes, especially mercury, which is known to be a neurotoxic pollutant.

The comments of the epidemiologist who led the California study, Dr. Robert Byrd, are telling:

"It is astounding to see a threefold increase in cases of autism with no explanation. There's a number of things that need to be answered. We need to rethink the possible causes of autism."

Your editorial stated that the scientific evidence supports the safety of thimerosal, a mercury-based preservative that until recently was used in many childhood vaccines. That statement isn't supported by the facts. Last year, the respected Institute of Medicine conducted a thorough review of the research on thimerosal and neurological disorders. The IOM determined that a connection was "biologically plausible" but that "the existing evidence is inadequate to accept or reject a causal relationship."

The good news is that thimerosal has now been removed from most childhood vaccines. The bad news is that the Food and Drug Administration waited so long to take action, resulting in exposure of millions of kids to unnecessary risk. In fact, the tremendous increase in autism coincided with the introduction of two additional vaccines containing thimerosal to the U.S. Children's Immunization Schedule in the late 1980s and early 1990s.

For those who consider thimerosal safe, here are a couple of interesting facts. The FDA considered this mercury compound so unsafe that it ordered it removed from over-the-counter topical ointments in 1985. Several European countries considered thimerosal so unsafe that they removed it from their vaccines in the early 1990s.

And yet, the FDA waited until 1999 to begin removing thimerosal from children's vaccines.

A number of internal government documents uncovered by my committee shed some light on the concerns about thimerosal that have developed over the last 20 years.

In 1980, an FDA advisory panel determined that thimerosal in ointments may cause cell damage: "The panel concludes that thimerosal is not safe for OTC (over the counter) topical use because of its potential for cell damage if applied to broken skin and its allergy potential."

In September 1998, almost a full year before the FDA did anything about mercury in vaccines, the FDA's Maternal Immunizations Working Group noted: "For investigational vaccines indicated for maternal immunization, the use of single-dose vials should be required to avoid the need of preservative in multi-dose vials. Of concern here is the potential neurotoxic effect of mercury, especially when considering cumulative doses of this component early in infancy."

In October 1998, the FDA official responsible for reviewing all scientific literature on the safety of thimerosal in vaccines observed: "I disagree with the conclusion regarding no basis for removal of thimerosal. (T)here are factors/data that would argue for the removal of thimerosal, including data on methyl mercury exposure in infants and the knowledge that thimerosal is not an essential component to vaccines."

In an internal briefing document from 2000, a government researcher states: "Preliminary screening for possible neurologic and renal conditions following exposures to vaccines containing thimerosal before three months of age showed a statistical association for the overall category of neurological developmental disorders and for two conditions within the category, speech delay and attention-deficit disorder."

It is unquestioned that overexposure to mercury in the environment causes neurological problems in developing children. Nobody knows if mercury used in vaccines has caused autism or related disorders. Much more research needs to be done to resolve this question.

It is very possible that a combination of factors is at work. Are some people genetically predisposed to vaccine injuries? Did mercury in vaccines combine with mercury in the environment to have a cumulative effect on some children? Is there a combination of environmental factors causing this epidemic of autism?

For the sake of autistic children and the parents who are struggling to raise them, we need to make it a national priority to answer these questions. Until we do, let's not rule anything out.

Burton represents the 6th District of Indiana in the U.S. House of Representatives and chairs the Government Reform Committee.