Another Mercurial Finding From the CDC

There’s a new study out on thimerosal, the controversial preservative once commonly used in vaccines. Whether or not thimerosal causes autism has been the cause of much debate, and this new study appears, at first, to reassure.

I have to admit, it’s a little intimidating to cover this topic. I know there are parents of autistic children out there who have researched thimerosal until they could get a Ph.D. on it, who catch the subtle nuances in each study, who could argue every point with the medical bigwigs until said bigwigs were left gasping on the floor. Nonetheless, I shall forge ahead, confident only in the knowledge that I’m probably missing some giant piece of the puzzle. I welcome, of course, your corrections or comments.

Let’s start with the inarguable facts

The rate of autism in children has increased at a staggering rate. There has been more than a ten-fold increase in the number of autism cases in the US in the past thirty years. Similar increases have been seen around the world. The part no one can agree on is why. One recent study suggests that autism is caused by exposure to high levels of testosterone in the womb, creating an “extreme version of the male brain.” Another study blames television: scientists found that autism rates shot up as cable television subscriptions increased, as well as in areas where it rained or snowed a lot, presumably keeping children indoors. (The scientists involved admitted, though, that other factors beyond television could be at play, such as indoor air pollution.)

The main contender, though, has been thimerosal, which is a mercury compound. Mercury is a known neurotoxin, but the type of mercury in thimerosal was thought to leave the system relatively quickly, before it could cause problems. The theory that many now hold—a theory which is supported by some studies— is that thimerosal may be shed by most children, but in some, the mercury builds up until it reaches dangerous levels.

Thimerosal was first introduced into vaccines in the early 1930s, after numerous children died from vaccination-related staph infections. It was phased out of most of them (not including, notably, the flu vaccine) in the late ’90s. As the number of vaccines in infancy and early childhood increased in the past thirty years, the cases of autism skyrocketed. In the late ’90s, the FDA found that some infants, depending on their vaccination schedule and their weight, had been exposed to levels of mercury that exceeded safety guidelines. Consequently, vaccine manufacturers were asked (not required) to reduce or eliminate thimerosal while further studies were conducted. (There is evidence that at least one manufacturer considered and then dismissed removing thimerosal years before: A leaked Merck memo (link is to PDF) from 1991 indicated that the company was aware of the mercury load in infants and children; Swedish researchers had concluded that the load could be eight-seven times the acceptable threshold, and that thimerosal should be removed. Nothing happened.)

Since that decision, the FDA and CDC have backtracked furiously, insisting that the phasing out of thimerosal was a precautionary measure and had no reflection on its actual safety. Meanwhile,several studies have concluded that thimerosal has no relationship to autism. Yet many child-health advocates and parents remain adamant that thimerosal is the hidden culprit. Many accuse public-health researchers of collusion with pharmaceutical companies. (In this latest study, four of the researchers have received fees from drug companies, and the lead author of the study once worked for Merck.) And they cite their own experiences, of watching their lively children withdrawing, becoming shadows of their former selves, weeks after their vaccinations. They also quote an intriguing study from 2006, which found that since thimerosal was removed from many vaccines, autism rates have gone down.

This latest study is being heralded as the final word on thimerosal. “Mercury-Containing Vaccine Vindicated!” crowed ABC News. (Hello, ABC? It’s not the vaccine that was being studied. Let’s get our facts straight.) In this CDC-funded study, 1,000 children between the ages of seven and ten, all of whom were exposed to various levels of thimerosal as babies, were assessed. The findings, according to ABC (and several other media outlets): there was little difference between those children and the ones with low exposure to thimerosal.
Conclusion? Thimerosal is absolutely safe! Let’s all have a thimerosal cocktail and call it a day!

One of the strangest aspects to this study is that it was not designed to address autism concerns. Which begs the question: uh, why not? When the vaccination/autism link has been so hotly contested in the past ten years, why would researchers go out of their way to study the effects of thimerosal on neurological functioning, and avoid testing for autism? Especially when they were thorough enough to study 42 aspects of neurological functioning?

Despite their express avoidance of the A word, there’s a fairly damning finding from the study that’s been glossed over by the media: the increase in facial tics associated with thimerosal. Boys who had been given vaccines with thimerosal were over twice as likely to develop tics. Over at the Huffington Post, journalist David Kirby, author of Evidence of Harm, points out this weird disconnect between the study’s findings and its conclusion. There are no neurological risks associated with thimerosal, they say, except for these, um, neurological risks. “Tics,” by the way, can involve anything from the occasional throat clearing to repetitive movements and sounds that eerily resemble many autistic behaviors. (The study authors didn’t specify what sort of tics were found.) As Kirby says, “…if ‘simple’ tics include head jerks and barking; and ‘complex’ tics can entail biting, banging and screaming obscenities; and if thimerosal can more than double the chance of tics in boys; then Atlanta, we have a very big problem.”

So it seems that this study isn’t the final word that the CDC hopes it will be. In addition to the tic behavior, the study has been criticized for its methodology: only 30% of approved families agreed to participate, a relatively low level, and the children were tested at a fairly late age, well after speech and other therapies might have (hypothetically) improved their functioning.
Let’s hope a definitive study comes out one of these days, if it ever does. I never thought myself a conspiracy theorist, but the more I read, the more inescapable one fact becomes: a study that found a link between thimerosal and autism would prove disastrous to the pharmaceutical industry, opening them up to billions of dollars worth of lawsuits. And that might be a good enough reason for everyone to keep their mouths shut, and their researchers obedient.