By day: mum of an autistic tot. By night: mum of an autistic tot.
This post is co-authored by the lovely science geek and bowling shark, Linda Tock. She provides the science and I have added the snark.
Every now and again, a study comes along which anti-vaccinationists are convinced proves that vaccines-are-the-worst-thing-ever hypothesis is more than a fantasy. These studies, like Christmas, tend to come around again and again. Though the one being discussed in this post is rpretty recent (June 2012), I’ve seen it cited time and time again. I’m bored of it already. I miss “rain mouse“, I even miss the monkeys.
The authors of Thimerosal-Derived Ethylmercury Is a Mitochondrial Toxin in Human Astrocytes: Possible Role of Fenton Chemistry in the Oxidation and Breakage of mtDNA explain, in some detail, how they took human astrocytes (star shaped cells from the brain) and, in simple terms, drowned them in thimerosal. Unsurprisingly, the cells didn’t fare too well.
It is a study that hinges on a presumption, not referenced or so far tested.
“We postulate that this compound is preferentially taken up into the mitochondria of NHA causing damage to the respiratory chain and subsequent ROS [Reactive Oxygen Species] production”
There are no studies that I can find in support of this and I’m not entirely sure what they’re basing it on as this study does not compare the uptake of thimerosal with any other compound.
This is an in vitro experiment. It’s done in a cell line in a lab in little plastic containers like these:this makes the focus of the study very specific i.e. those particular cells and their reaction to thimerosal. It does not take into account the rest of the organism – the circulatory system, the liver, etc – so there is no adsorption, distribution, metabolism or excretion (often called just ADME) here.
If we look at Figure 1 of the study (which is actually mislabeled a/b wise in the ‘window’ of the study – but that’s neither here nor there), we see two graphs. The top (a) graph shows the changes in mitotracker and ROS induced DCF levels as the concentration of thimerosal increases. Since they don’t actually say specifically anywhere in the paper, I’m taking DCF to stand for 2,7-dichlorofluorescein.
So how much ethyl mercury was there?
At a concentration of about 2.5 uM (micro molar) we see a definitive (ie: significant) upswing in the fractional change, which is sustained through about 7.5 uM before it begins to tail off.
How much mercury (Hg) is in 2.5 uM of ethyl mercury?
uM = umol/L
(2.5 umol Et-Hg/L) * (1 umol Hg/1 umol Et-Hg) * (202.59 ug Hg/1 umol Hg) = 506.48 ug Hg/L
There’s 1 mole of Hg for every 1 mole of Et Hg, so there must be 1 micromole of Hg for every micromole of Et-Hg, and there’s 202.59 grams of Hg per mole of Hg, therefore there must be 202.59 micrograms of Hg per micromole of Hg.
So, we have 506.48 ug of Hg in each L.
So now what?
Well – we don’t know how relative that number is, so, we have to ask:
How does it compare to other studies of mercury?
Let’s compare that figure with the levels of Hg found in this study: Mercury levels in premature and low birth weight newborn infants after receipt of thimerosal-containing vaccines which looks the excretion and blood concentrations of mercury. This is relevant, because you cannot get mercury into or past the blood-brain barrier without it being in the bloodstream. Taking Figure 1. The highest amount of blood mercury recorded during this study was roughly 7.6 ng/mL. How does that compare to our 506.48 ug/L from the previous study?
Well, that’s rather simple. 1 ng/mL = 1 ug/L. So, the highest amount of blood mercury in the preemies in that study was 7.6 ug/L. (It’s also interesting to note that the stools contained 10 times the amount of mercury – on average – than the blood).
(506.48/7.6) = 66.6
The lowest amount of mercury which caused ROS generation in those astrocyte cells was over 60 times the amount of mercury found in the bloodstream of infants within 48 hours of vaccination. The *average* amount of mercury found in those infants was 3.6 (+/- 2.1) ng/mL or 3.6 ug/L. That means that the cell lines were exposed to 140 times (on average) the amount of mercury than what is found in the bloodstream of premature, low birth weight babies 48 hours after vaccination. So, while direct application of thimerosal might induce ROS generations in a cell culture line, the amounts of thimerosal used for the study are not representative of the typical exposure window, nor do they account for the other biological factors (ADME) which can influence the toxicity to the cell line.
Liz Ditz also has a post on this at her beautiful blog, I Speak of Dreams