This post examines a newly published article that claims that ethylmercury (in this case, thimerosal or thiomersal) crosses the blood-brain barrier (BBB). Of course, it comes from anti-vaccine non-scientists.
As we recently celebrated the 10th anniversary of the retraction of the fraudulent study from Andrew Wakefield and colleagues  (retraction notice), this celebration is only half-tone as we have seen more and more an influx of junk studies coming from a new breed of anti-vaccine “scientists” (such as Christopher Exley, Christopher Shaw, James Lyons-Weiler, Romain Gherardi, Yehuda Shoenfeld, Walter Lukiw, citing the most prolific of the bunch) take over the torch and publish deeply flawed studies, if not completely fraudulent in peer-reviewed journals.
Worse, we have seen indeed that some journals, such as the Journal of Inorganic Biochemistry or Journal of Trace Elements, have become a hive of anti-vaccine pseudoscience for studies as presented in their published form. They should not have passed a peer-review filter.
Yet, these journals have accepted these articles, despite their important factual errors, botched experimental design and inaccurate conclusions which are not supported by the experimental results. I recently got wind that the infamous Geiers are up into flogging a dead horse once again, this time with the benediction of the journal Environmental Toxicology and Pharmacology .
If this article was published in a low-tier or a predatory journal, I would understand. But seeing a paper authored by a quack doctor that lost his medical license to practice in 2012 (you can read the detailed case of his disciplinary action here), as well as the recent retraction of a study, with three out of the four authors accused of gross negligence on the claims made and failure to disclose a conflict of interest.
This should have been a red flag for the editor-in-chief and reviewers. Yet, we have a situation similar to the canary in the coal mine, this time about the canary slowly suffocating from the methane slowly leaking into the shaft, but no one taking action.
Seeing the field of academic publishing allowing such biased and non-sequitur review to be published (albeit being in review/revision for 4 months) is concerning. Quacks and charlatans are invading peer-reviewed journals, with the dangerous blessing of their editors and reviewers.
Does this review which was written by the Geiers, the Thenardiers of “autism treatment” (see Note 1), hold up or is completely full of logical flaws?
Let’s give it a read.
We have basically what I would call the “unholy trinity” made of Geiers (father and son), with Janet Kern being the “unholy spirit” (you can get a glimpse into her beliefs here). These authors had been publishing a lot together up through 2009, a time when talking “mercury” in vaccines (ethylmercury in the form of thimerosal) was trendy, which was about the time that Wakefield paper got retracted.
All three are affiliated with the “Institute of Chronic Illness Inc. ”, another basement in someone’s home posing as an “institute”. I also want to mention that our “unholy Trinity” got a retraction on their 2017 paper, the only paper published by the triad from 2009 until now.
So, I will raise huge red flags about this “study” by writing my post as a letter to the editor.
About ethylmercury crossing the BBB
I am writing this letter of concern in regards to a recent review by Geier DA and colleagues that was recently published in your journal with the title “Examining the evidence that ethylmercury crosses the blood-brain barrier.”
The whole premise of their review was written following the recent publication by Boom and colleagues which addressed vaccine myths, with a particular emphasis on the transport of ethylmercury (a byproduct degradation of thimerosal).
In their review, the authors accurately state that “ethylmercury does not cross the blood-brain barrier and is structurally different from methylmercury…”. Geier and colleagues inaccurately disputed this statement (further underlined by the absence of citations supporting that claim).
However, the rebuttal written by the authors is not only as factually incorrect as the statement made by Bloom and colleagues but also pertains to a vaccine myth about the toxicity of ethylmercury (and thimerosal), by maintaining the fallacious claim that “MMR in vaccines contributed to autism in children” from the disgraced Dr. Andrew Wakefield, which has recently celebrated the 10th anniversary of the retraction of his fraudulent study published in The Lancet .
Before I further discuss my rebuttal of this review and raise my concern on this publication, I would like to underline that recently three out of four authors have a review paper retracted from publications on two stipulations:
- failure to disclose conflicts of interests and
- “mistakes of various types that raise concerns about the validity of the conclusion”, quoting the retraction notice .
In addition, I also feel it is important to disclose the revocation of the license to practice medicine by the Maryland Board of Physicians on April 27, 2011, on the basis of serious practice and ethical violations committed by the authors.
Due to the important volume of factual inaccuracies and violations committed in this reviews, and due to my limited knowledge expertise in the field (despite having credentials in the field of the blood-brain barrier research, including over 30 peer-reviewed studies in the field), I will limit my rebuttal to the in vitro (referred as “cellular studies”) in the review.
Cellular studies section
The first factual inaccuracy pointed by the authors is aimed to let the reader conclude that up to the recent study published by Zimmermann and colleagues in 2013 , there were no studies that assessed the transport of ethylmercury (inorganic and organic forms) across the blood-brain barrier and therefore concluded about the inability of ethylmercury to accumulate into the brain, as quoted as:
As early as 1987, Aschner and Clarkson found that methylmercury-containing compounds were translocated across the BBB by the neutral amino acid carrier transport system. That finding was confirmed by other studies in the 1990s, e.g., Kerper et al. (1992). So, for many years, until about 2013, many believed the paradigm that methylmercury-containing compounds were actively transported across membranes by the LAT transport system, but ethylmercury-containing compounds were not. This assumption was found to be wrong in a study by Zimmermann et al. (2013).
The first item of concern is the omission of key elements from the existing literature, the authors omitted to cite the work of Magos and colleagues that reported blood and brain concentration of both methylmercury (MeHg) and ethylmercury (EtHg) and damage in rat pups cerebellum following five daily doses of 8mg Hg/kg .
This study was later cited in the review study by Clements in 2004 , in which the author compiled the amount of ethylmercury exposure from vaccines during the first year of infancy and concluded that such levels (as projected blood levels) remained below the recommended maximum levels established by the CDC.
Also, the authors failed to correctly cite the work of Burbacher and colleagues in this particular paragraph . Such omission of the citing of important literature and spinning it in opposition to the existing literature is a serious concern that should have been addressed by the reviewers.
The second item of concern is using the Zimmerman study as a ground for discussing the transport of ethylmercury across the blood-brain barrier (BBB). Zimmermann only documented the uptake mechanism of organic mercury in vitro using C6 rat glioma cells, in place of an in vitro model of the BBB (despite the availability of various protocols capable to isolate primary brain microvascular endothelial cells from rodents, porcine or bovine sources).
C6 glioma is technically an isolated rat astrocytoma cell line by Benda and colleagues in 1968 . This study provides useful insights into the mechanism of uptake of organic mercury species in neuronal and non-neuronal cells, which could be extrapolated to the BBB (as LAT1 expression occurs at the BBB as well).
However, this study cannot be solely used to make the claims made earlier and failed to provide results on the interactions on the BBB and mercury compounds. I also feel the need to emphasize that both doses and exposure frequencies are tenets of toxicology.
The EC50 values reported by Zimmerman are 4.83 and 5.05 µmoles/L for MeHg (methylmercury) and EtHg (ethylmercury) respectively. Assuming that both species crosses the BBB with a 100% uptake efficiency, these would suggest a CSF value of approximately 1075 µg/L and 1162 µg/L, and by extrapolation similar blood level concentrations.
Such levels are not only 30-100 times higher than values reported by Burbacher and colleagues, but is significantly higher (200 times higher) than the value reported by Pichichero and colleagues in newborns following HBV and BCG vaccination at birth, with a mercury level reported 0.5 days post-injection of 0.3-0.5microg/L .
Although the study by Zimmerman has merits in elucidating the mechanism of uptake of mercury in brain cells, it limited translational relevance to make claims on ethylmercury toxicity should have been mentioned by the authors, but coincidentally omitted from discussion. Again, this gross negligence should have been picked by reviewers.
The third item of concern is this quote from the authors:
Zimmermann et al. (2013) compared the toxicities induced by methylmercuric chloride and ethylmercuric chloride, as well as by their complexes with cysteine (MeHg-S-Cys and EtHg-S-Cys) in neuronal cells.
This is another gross mistake done by the authors and raises the question if the authors actually read the literature cited beyond the abstract and titles. This study mostly examined the toxicity of ethylmercury on C6 cells, as mentioned above.
Ontogenically, these are astrocytes and commonly used as a cheap source of astrocytes as a co-culture system to enhance barrier properties of in vitro models of the BBB . Astrocytes and neurons are ontogenically distinct cell types, despite sharing a common ancestor (both originate from neural stem cells).
A better in vitro model for neurotoxicity would be to use primary cultures of hippocampal neurons (using fetal mice at E15 stage) or the use of immortalized neuron-like cells such as PC12 (isolated from a rat pheochromocytoma) or SH-SY5Y (human neuron-like cells).
This factual inaccuracy tells me that none of the authors read the actual study (despite being freely accessible via PMC), nor the reviewers paid attention to bibliography accuracy. As a reviewer, this is an unacceptable mistake made by at least two of them (assuming only two reviewers read that manuscript).
The fourth and final item of concern is the citation of the work by Lohren and colleagues . The use of a porcine model of the BBB is pretty common, through today, even after the publication of several studies using an in vitro model of the BBB based on induced pluripotent stem cells (hiPSCs) [12-15].
It is popular in drug discovery for two reasons:
- it is very easy to obtain a lot of stem cells (if you have a contact with your local slaughterhouse and have a couple of lab technicians that are used to doing such isolations), and
- these primary cells form pretty good BBB monolayers with satisfactory barrier tightness, TEER (Transepithelial/transendothelial electrical resistance) >1000 Ohms/cm2 to ensure these monolayers are leaky.
The major caveat being these cells are from porcine origin, we cannot exclude differences between pig BBB and human BBB in terms of transporters. Again, the authors did not read the same paper as I did, because the paper tells me a different story.
Judge for yourself.
The authors have measured changes in the impedance (electrical resistance) as a sign of distress in the BBB monolayers either given in the apical (top) chamber (left panels) and in the basolateral (bottom) chamber (right panels). This is what the authors said:
…reported that all three species of mercury had cytotoxic effects in the barrier building cells; however, the most damage was caused by the organic species. They found that methylmercury chloride and Thimerosal crossed the barrier in both directions, with a slight accumulation in the basolateral, brain-facing compartment, after simultaneous incubation in both compartments.
Firstly, although all three species showed signs of toxicity, one of them showed a remarkable lack of toxicity at concentration deemed reasonable (and by reasonable, I mean here concentration such as 10 µmoles/L, which is about 200 times the maximum concentration of ethylmercury reported in the Burbacher study) upon treatment in the apical chamber.
Both Hg and MeHg showed severe signs of toxicity at 3 µoles/L, whereas nothing meaningful was observed in the EtHg-treated group that received 10 µmoles/L.
Basolateral treatment showed slightly different results, with toxicity for Hg visible at 3 µmoles/L, 1 µmoles/L for MeHg and 100 µmoles/L. Therefore, we should conclude that thimerosal appears to be 33x less toxic than Hg, and 100x less toxic than MeHg.
Indeed, we should conclude that not all organic forms of mercury are toxic, and MeHg indeed appears the most toxic form. This has been known for decades now, and therefore, it is a public health measure to recommend the limited consumption of fish and seafood in pregnant women (because MeHg is notoriously known to bioaccumulate).
After this exhaustive critique that only covered a fraction of the published review, I hope dear editor that I have provided enough evidence to have you reconsider this publication and demand further clarifications from the authors.
As we celebrate the 10th anniversary of the retraction of Dr. Wakefield publication from The Lancet, and the subsequent damage that such paper has done to public health by giving a momentum to vaccine hesitancy and anti-vaccine movement, we must, as scientists, be sure the information published in academic publishing is upheld at the highest standards of factual accuracy and ethical integrity. I hope we can learn from our mistakes and restore faith in our peer-reviewed system by demanding every author to uphold to the highest standards of publications.
A concerned scientist.
Considering the sloppiness of the review by Kern et al., which is obvious by just the 6th page of the manuscript, I would not want to waste my time on this.
Seeing such gross factual inaccuracies, for example, with respect to the in vitro studies, clearly denotes two things:
- the authors are citing studies without citing them properly. They gave little attention and details to the content of the papers and seem that they validated them only by reading their abstracts.
- the failure to properly cite and summarize such studies in a review, and have such inaccuracies passed peer-reviewed filters really concerns me as a reviewer and makes me question the quality of this journal’s editorial process.
Should I speculate that a letter to the editor and a subsequent retraction notice should be on sight? I would like to assume so.
The problem is the harm has been done. Even after retraction, the authors will enjoy playing the martyr, sacrificed by the scientific community for “speaking the truth”. Again, the Geiers showed us what they are best at being – manipulative, cherry-picking the literature (and in a very poor fashion), make extraordinary claims and ultimately flogging a dead horse “thimerosal in vaccines cause autism”.
We once again see that the anti-vaxxers using “scientists” who have long ago forsaken their ethics and scientific integrity for personal gains, while poisoning the well with studies and reviews that are botched and misrepresented the literature, while posing as “science” in the eyes of the anti-vaccine community.
- The son David A Geier was found guilty of practicing medicine without a license. The dad Mark R Geier pushed the diagnosis and medical examination of autistic children over the phone then experimented with “chemical castration” (Lupron®). This treatment of children with autism spectrum disorder in such a manner is abhorrent.
This article is by VaultDwellerSYR, a pseudonym used by a faculty member of a School of Pharmacy within a large medical school. They have significant research and publications in the effect of certain chemicals on the brain. Although we are opposed to all arguments from authority, the author has a substantial record of actual, published research in this field of brain cell biology and biochemistry.
The author has stated that he has no conflict of interest to disclose.
- Wakefield AJ, Murch SH, Anthony A, Linnell J, Casson DM, Malik M, Berelowitz M, Dhillon AP, Thomson MA, Harvey P, Valentine A, Davies SE, Walker-Smith JA. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 1998 Feb 28;351(9103):637-41. doi: 10.1016/s0140-6736(97)11096-0.
- Kern JK, Geier DA, Homme KG, Geier MR. Examining the evidence that ethylmercury crosses the blood-brain barrier. Environ Toxicol Pharmacol. 2020 Feb;74:103312. doi: 10.1016/j.etap.2019.103312. Epub 2019 Dec 9. Review. PubMed PMID: 31841767.
- Kern JK, Geier DA, Deth RC, Sykes LK, Hooker BS, Love JM, Bjørklund G, Chaigneau CG, Haley BE, Geier MR. RETRACTED ARTICLE: Systematic Assessment of Research on Autism Spectrum Disorder and Mercury Reveals Conflicts of Interest and the Need for Transparency in Autism Research. Sci Eng Ethics. 2017 Dec;23(6):1689-1690. doi: 10.1007/s11948-015-9713-6. Epub 2015 Oct 27. Review. PubMed PMID: 26507205; PubMed Central PMCID: PMC5705728.
- Zimmermann LT, Santos DB, Naime AA, Leal RB, Dórea JG, Barbosa F Jr, Aschner M, Rocha JB, Farina M. Comparative study on methyl- and ethylmercury-induced toxicity in C6 glioma cells and the potential role of LAT-1 in mediating mercurial-thiol complexes uptake. Neurotoxicology. 2013 Sep;38:1-8. doi: 10.1016/j.neuro.2013.05.015. Epub 2013 May 30. PubMed PMID: 23727015; PubMed Central PMCID: PMC4922646.
- Magos L. Neurotoxic character of thimerosal and the allometric extrapolation of adult clearance half-time to infants. J Appl Toxicol. 2003 Jul-Aug;23(4):263-9. doi: 10.1002/jat.918. Review. PubMed PMID: 12884410.
- Clements CJ. The evidence for the safety of thiomersal in newborn and infant vaccines. Vaccine. 2004 May 7;22(15-16):1854-61. doi: 10.1016/j.vaccine.2003.11.017. Review. PubMed PMID: 15121295.
- Burbacher TM, Shen DD, Liberato N, Grant KS, Cernichiari E, Clarkson T. Comparison of blood and brain mercury levels in infant monkeys exposed to methylmercury or vaccines containing thimerosal. Environ Health Perspect. 2005 Aug;113(8):1015-21. doi: 10.1289/ehp.7712. PubMed PMID: 16079072; PubMed Central PMCID: PMC1280342.
- Benda P, Lightbody J, Sato G, Levine L, Sweet W. Differentiated rat glial cell strain in tissue culture. Science. 1968 Jul 26;161(3839):370-1. doi: 10.1126/science.161.3839.370. PubMed PMID: 4873531.
- Pichichero ME, Gentile A, Giglio N, Umido V, Clarkson T, Cernichiari E, Zareba G, Gotelli C, Gotelli M, Yan L, Treanor J. Mercury levels in newborns and infants after receipt of thimerosal-containing vaccines. Pediatrics. 2008 Feb;121(2):e208-14. doi: 10.1542/peds.2006-3363. PubMed PMID: 18245396.
- Török M, Huwyler J, Gutmann H, Fricker G, Drewe J. Modulation of transendothelial permeability and expression of ATP-binding cassette transporters in cultured brain capillary endothelial cells by astrocytic factors and cell-culture conditions. Exp Brain Res. 2003 Dec;153(3):356-65. doi: 10.1007/s00221-003-1620-4. Epub 2003 Sep 12. PubMed PMID: 14610630.
- Lohren H, Blagojevic L, Fitkau R, Ebert F, Schildknecht S, Leist M, Schwerdtle T. Toxicity of organic and inorganic mercury species in differentiated human neurons and human astrocytes. J Trace Elem Med Biol. 2015 Oct;32:200-8. doi: 10.1016/j.jtemb.2015.06.008. Epub 2015 Jul 15. PubMed PMID: 26302930.
- Aday S, Cecchelli R, Hallier-Vanuxeem D, Dehouck MP, Ferreira L. Stem Cell-Based Human Blood-Brain Barrier Models for Drug Discovery and Delivery. Trends Biotechnol. 2016 May;34(5):382-393. doi: 10.1016/j.tibtech.2016.01.001. Epub 2016 Feb 3. Review. PubMed PMID: 26838094.
- Wilhelm I, Krizbai IA. In vitro models of the blood-brain barrier for the study of drug delivery to the brain. Mol Pharm. 2014 Jul 7;11(7):1949-63. doi: 10.1021/mp500046f. Epub 2014 Apr 18. Review. PubMed PMID: 24641309.
- Naik P, Cucullo L. In vitro blood-brain barrier models: current and perspective technologies. J Pharm Sci. 2012 Apr;101(4):1337-54. doi: 10.1002/jps.23022. Epub 2011 Dec 27. Review. PubMed PMID: 22213383; PubMed Central PMCID: PMC3288147.
Please help me out by sharing this article. Also, please comment below, whether it's positive or negative. Of course, if you find spelling errors, tell me!
There are two ways you can help support this blog. First, you can use Patreon by clicking on the link below. It allows you to set up a monthly donation, which will go a long way to supporting the Skeptical Raptor
Finally, you can also purchase anything on Amazon, and a small portion of each purchase goes to this website. Just click below, and shop for everything.