The Autism-Mercury Connection--Dr. Brent at the Omnibus Autism Proceeding

In the first test case at the Omnibus Autism Proceeding, concerning whether the administration of thimerosal-containing vaccines in combination with the MMR vaccination could have caused Michelle Cedillo's autism, Dr. Jeffrey Brent testified that it could not. But, on the way to getting there, he explained, in simple language, some of the issues concerning mercury toxicity which are important to understand. I also believe that one of his answers, while technically not incorrect, is open to criticism for not being complete and helpful. Thus, this essay will focus first on his testimony and then on his "silence."

The Nature of Thimerosal.

Thimerosal, in brief, is a preservative that has been widely used as a pharmaceutical since the 1920s. During WWII field surgeons learned that severe gunshot wounds, leading to massive blood loss, need not be fatal if the blood could immediately and aggressively be replaced with blood plasma. That blood plasma was preserved with thimerosal, to the benefit of all.

Thimerosal is different from ethylmercury. Chemically, thimerosal is ethylmercury thiosalicylate. As soon as it gets into the body the bond between the two chemicals, which is relatively weak, breaks and "thimerosal becomes ethyl mercury plus thiosalicylate," p. 2314. The attorney then asked Dr. Brent about a rule in the Code of Federal Regulations (21 CFR 310.545) which referred to thimerosal. Brent responded that this rule, from the early 1980s, was a sort of "grandfather-clause" where about 700 substances that had been used medicinally over the years just went through a "grandfathering process" of being approved without the FDA doing a formal assessment of their safety. Thimerosal was one of the 700 substances approved without testing. He gave some other examples: aspirin, lidocaine, caffeine, calcium salts, iron salts. "Almost all the vitamins in your daily vitamin pill are on that list." In addition one has wheat germ and garlic. The defense attorney asked if the regulation was in any way relevant to demonstrate that doses of thimerosal or thimerosal-containing vaccine are unsafe. His response: "There is nothing in this regulation that says that," p. 2318.

Dr. Brent explained that there was a three-step procedure used by certified medical toxicologists to determine if a certain chemical has caused a certain outcome. First, "What was the patient exposed to?" Second, "Can the exposure under any circumstances cause the patient's disease?" And, third, "Did that particular chemical, in this particular patient under these circumstances, cause this disease?" p. 2320.

He then explained the difference between in vitro (petri dish) and in vivo (living body) studies. It isn't safe to extrapolate from in vitro results to in vivo results, principally because the living organism may have a host of other defenses to rally to it but when a single cell or molecule is isolated in a petri dish it may not have that same capacity. So, administrying ethyl mercury to an intact animal is qualitatively different than administering it to some animal cells in a petri dish. The scientific concept can be stated as follows: "Demonstration of an adverse effect of mercury in vitro does not readily translate into a physiologic argument," p. 2323. Dr. Brent went through this basic principles in order to explain his disagreement with two studies (which I won't go into here, but which are discussed in the testimony--the Goth and Agrawal studies).

The Holmes Study

But my real interest is how he responded to Dr. Amy Holmes' study of the mercury amounts in first-cut hair of autistic vs. neurotypical children. This begins on p. 2351. Some people have used the term "efflux disorder" to describe the condition of children with difficulty excreting mercury. Brent would later testify that this term is not recognized in the relevant international disease classification system (the "ICD"--International Classification of Diseases) but he first looked at the Holmes study. "It is important to note that much better studies from other investigators could not replicate the results...of the Holmes study," p. 2351. He summarized the Holmes study as I have done so: the "hair levels" of the autistic children (i.e., mercury in the hair) was about "0.47 parts per million. If you look at the normal control, the hair levels averaged about 3.6 parts per million." He responded:

"Now, if you look at this data you're immediately struck by the fact that something must be very, very wrong here because there's a very excellent, huge study..(the NHANES study)...that surveyed hair levels of mercury in the US population in children..you see that the average is about 0.22 parts per million, remarkably close to what was reported in the Holmes study for the autistics," p. 2352.

But the data for the controls was "highly nonrepresentative" of the general population in the United States. Then, in a statement I didn't fully understand, Dr. Brent said that hair samples are not a good method of measuring mercury. "Hair is not a significant excretory organ for mercury," p. 2353. But the NHANES study said that "Hair Hg concentration is the preferred biomarker for evaluating Hg exposure for extended periods of time..." So, the thing that confuses me here is if there is agreement on what the value of measuring mercury content in hair is... This is an important question to answer, but it isn't clarified here. In any case, he pointed out two published studies that show no difference in hair mercury levels between autistics and controls (Kern and Ip studies, the latter from Taiwan). It is because of this kind of disparity that Dr. James Adams of Arizona State did his replication of the Holmes study, which was just published this week. The next essay reviews that study.

An Unresolved Question in Dr. Brent's Testimony

In general, I think that Dr. Brent clearly explained the role of thimerosal in vaccines and made a credible case for why the level of thimerosal was not itself responsible for Michelle Cedillo's autism. But there was one part of his testimony that I don't think was quite accurate or complete. His attorney posed the question:

"I want to turn now to Dr. Aposhian's [expert witness for the Cedillo family] hypothesis that there is a genetically susceptible subpopulation to mercury in autistic spectrum disorder. To your knowledge, is there any evidence that supports this hypothesis?" p. 2363. Answer: "I have found none."

That isn't really an answer to the question. He does try to answer it more fully in the next page, but he really doesn't do so. And, indeed, as autism research is progressing in 2008 it is precisely this issue that is receiving attention. That is, there may be "genetically susceptible subpopulations" of children who are immunized so that, when immunized, something is "triggered within" that results in symptoms that would later be diagnosed as autism. As the Hannah Poling case shows (I will write on her at a later date), the Government conceded that she had an underlying mitochondrial condition that was exacerbated by a childhood vaccine--that led to her autistic behavior. So, this is the key now to a lot of attention on the "autism question" in 2008. Perhaps the mercury in vaccines per se isn't the causal factor in all 4,800+ cases that are before the Court of Federal Claims, but perhaps the mercury or the excessive number of vaccines interacts with something in the genetic makeup of the child, a sort of susceptibility that no one really could have figured out before the vaccination, that led to the development and manifestation of autistic symptoms. It would have been helpful had Dr. Brent admitted as such.

But what you learn in law, and especially what you learn as a litigation attorney, is that courtroom drama isn't really an impartial search for truth. You don't "tell all." You might tell the "whole truth" but that doesn't mean you tell everything that is true.

Conclusion

Though it is too early to conclude much of anything regarding the OAP, I can see how a sort of "new hypothesis" regarding autism is emerging: that mercury in vaccines may not "cause" autism, but that it might interact in a genetically susceptible subset of people with genetic markers or faults in order to produce symptoms which we would them call autistic. Mercury didn't "cause" autism in most vaccinated children; but it may have interacted with something in the "system" of many children in such a way that autism resulted. It is that "something" that is a central focus of discussion now.

But the mercury issue, apart from vaccines, isn't "dead" yet. Dr. Adams' study, trying to replicate Dr. Holmes 2003 study, was just published. The next essay reviews his study and its findings.

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