Mercury poisoning and autism--second essay

The "mercury issue," or how mercury toxicity might relate to the development and manifestation of autistic symptoms, can further be broken down into various kinds of mercury that are thought to be the culprit: thimerosal-containing vaccines, dental amalgams (especially if a pregnant mother has them inserted during pregnancy) and fish consumption during pregnancy. Allied issues are the potential toxicity of Rho-gam procedures during a woman's pregnancy, and the administration of antibiotics to small children/babies who might have a genetic susceptibility to developing autistic symptoms. It should also be noted that one vaccine that has also be accused of contributing to autistic symptoms in children, the MMR or "measles, mumps, rubella" vaccine, never had any mercury-containing thimerosal in it, and so it is not strictly a "heavy-metal excretion" issue, though it is one of host of vaccine-related issues in autism.

Thimerosal--What Is It?

Thimerosal is a mercury-containing organic compound which has been widely used, since the 1930s, as a preservative in a number of drug products, including vaccines. Thimerosal breaks down or metabolizes into just under 50% ethylmercury and thiosalicylate. Ethylmercury should be distinguished from the more-frequently studied methylmercury, an organic compound that brings mercury into the body primarily through fish consumption. One of the flashpoints in the controversy over thimerosal is that there were few independent studies on its toxicity; it was simply assumed that the health risks from methyl and ethyl mercury were the same. As this web site says, "More research is needed to determine if the guidelines for methyl mercury are also appropriate guidelines for thimerosal."

Why was thimerosal, with the potentially dangerous mercury, ever put into vaccines beginning in the early 1930s? Well, because of an event in 1928. According to the story told here:

"In January 1928, in the early stages of an immunization campaign against diphtheria, Dr. Ewing George Thomson, Medical Officer of Health of Bundaberg [Australia], began the injection of children with toxin-antitoxin mixture. The material was taken from an India-rubber-capped bottle containing 10 mL of TAM. On the 17th, 20th, 21, and 24th January, Dr. Thomson injected subcutaneously a total of 21 children without ill effect. On the 27th a further 21 children were injected. Of these children eleven died on the 28th and one on the 29th."

Panic ensued and, after a Royal Commission implicated the cause of death as the injection of living staphylococci into the unfortunate children, demand was high for something that would not only eliminate the risk of contamination of vaccines but also bring minimal to zero health risks to those injected by vaccines. Thimerosal was proposed and, over the years, became one of the most widely used preservatives in vaccines. To be clear, vaccines are generally stored in "multi-vial" dosages, and thimserosal is injected into the solution; none is necessary, I have read, for single-dose vaccines.

No one, really, might have questioned the danger of thimerosal had not the explosion in number of cases of autism in the 1980s and, especially the 1990s and 2000s, resulted in about 2/3 of autism cases being instances of "autistic regression" (i.e., where the child develops "normally" until about 18 months of age, and then "regresses" into autistic symptoms) and only 1/3 being "autism from birth" cases. This reversed a long-standing ratio of incidence of autism cases. In addition, those who had watched the multiplication of required childhood vaccines from the 1980s and 1990s, and realized that some of these vaccines had more than trace amounts of thimerosal (such as the Hepatitis B, HiB; but here is a problem. Of the tons of vaccines listed in various places online, the closest I could come to a list of those containing more than a trace amount of thimerosal was this list, supplied by the FDA, which makes the problem look very small indeed. Someone, please, supply with better information, if you have it), were worried.

When people began to put these two factors together, they screamed, or, more accurately, some groups representing the interest of autistic families, objected. They advanced the hypothesis that the thimerosal-containing vaccines and the number of mandated vaccines combined to overload a child's system with more mercury than federal guidelines allowed. Since many children seemed to develop autistic-like symptoms directly after a vaccine injection (either a thimerosal-containing vaccine or the MMR), the hypothesis was advanced that the excessive mercury in the vaccines actually caused their child's autism or, possibly, triggered a genetic susceptibility to autism.

Widespread confusion, accusation, allegation of cover-up by federal authorities and increasing panic ensued. By the late 1990s, under pressure from families with autistic children, the Public Health Service (FDA, NIH, CDC etc.) decided to require vaccine manufacturers to reduce and then eliminate thimerosal in vaccines as soon as possible. By 2001, it was supposedly eliminated from all childhood vaccines, except one for influenza.

While this was happening, people were scrambling to come up with studies that showed either the relative harmlessness of thimerosal in vaccines (the government position) or the danger of it (the parents' position). One nearly sure way to test the hypothesis, as most now realize, is to take the CA data base, considered the best at collecting cases of autistic children in a state, and compare numbers of autistic children in the years prior to elimination of thimerosal from vaccines and the years afterwards. Though it is too early for a definitive answer to the question, most researchers have concluded that the numbers of autistic children in CA has not signficantly declined; even the rate of increase has not much, if at all, declined. Those groups which have put a lot of effort into the thimerosal-autism connection have raised doubts about the numbers or the interpretation of them; one father-son research duo, whose work seems to be trashed by every scholarly survey of studies in this area, says that the CA autism numbers have declined. I have no definitive guidance on the issue, but I think it is fair to say that since the mercury-thimerosal-autism parents haven't been making lots of noise on this issue in the past two years, that the numbers really aren't in their favor.

Conclusion

Rather than taking this as a setback or a bad sign, I think that parents and researchers might conclude that the etiology of autism is simply too complicated at this point to indicate a simple offender as the "culprit" for it. Perhaps in some cases it was a thimerosal-containing vaccine that tipped a child "over the edge." Parental testimony in this is important, but perhaps it is simply too complex an issue now to understand with the kind of precision for which science longs.

But the thimerosal controversy put the issue of mercury toxicity squarely in the front and center of the autism research agenda. The next essay will show how that research agenda has developed in the last seven or eight years.

3639