Thiomersal (also thimerosal in the U.S.) is the sodium salt of an organomercury compound (chemical name: sodium ethylmercuric thiosalicylate) and is used as a preservative in cosmetics and pharmaceuticals to prevent microbial growth. It is already effective in very small concentrations.
Thiomersal is degraded into thiosalicylate and ethylmercury in the body. The ethylemercuric cation (particle with a positive charge) blocks the activity of enzymes. This results in an antimicrobial effect (see Wikipedia Article Thiomersal https://en.wikipedia.org/wiki/Thiomersal) even at low dosages.
Thiomersal is a preservative licensed for use in cosmetic products in Austria. Its maximum limit is 0.007 % (calculated as mercury) -- i.e. 0.07 mg/g or ml. Should other mercury-containing compounds be used, the maximum level of mercury must not exceed a total limit of 0.007 %. Its application in eye cosmetic products (eye make-up and eye make-up removal products) is limited. Furthermore, the product must be labeled with a warning such as "enthält Ethylquecksilberthiosalicylat" (contains ethylmercuric thiosalicylate) or "enthält Thiomersal" (contains thiomersal). While the substance is basically licenced on the Austrian market under the conditions mentioned above, the use of thiomersal in cosmetic products in Austria is not that common.
In terms of medical applications, thiomersal is still used as a preservative in the influenza vaccines “Daronrix”, ”Pandemrix”, “Prepandrix”, “Pumarix” and the combined vaccine “Tritanrix HepB” used to treat diphtheria, tetanus, pertussis (whooping cough) and hepatits B. All such vaccines are licenced centrally for all EU Member States and are – with the exception of Tritanrix HepB – pandemic/pre-pandemic vaccines, which are not used on a routine basis. “Daronrix” contains 0.05 mg, “Pandemrix” 0.005 mg, “Prepandrix” 0.005 mg and “Pumarix” 0.005 mg thiomersal per packaging unit.
Thiomersal could also be present in traces as a residue from manufacturing. However, this would affect only very few products, if any, and would very likely be below levels where it could be detected. There are no maximum limits or test methods defined in neither the European Pharmacopoeia nor other European guidelines. Even so, manufacturers are obliged to state the presence of thiomersal in a product.
First doubts on the harmlessness of thiomersal were raised at the end of the 1990s: firstly, because of increasing reports of undesired effects, such as hypersensitivity reactions, but also because of accumulating mercury contamination in children caused by routine child vaccinations, which was feared to cause adverse neurologic effects, such as autism. Governmental agencies in the U.S. and Europe recommended removing thiomersal and other organic mercury compounds from vaccines for newborns and infants as a preventive measure, without any conclusive evidence of neurologic toxicity1. As a result, children under the age of six are only administered vaccines that contain no thiomersal or only traces of the substance in the USA. In general, most vaccines in individual dosage packaging in the USA are thiomersal-free2.
The European Medicines Agency committee revised its assessment of thiomersal in vaccines in 2004. The evaluation of epidemiologic studies led to the conclusion that there is no connection between neurologic development disorders and thiomersal in vaccines. Still, the development of vaccines without mercury-containing auxiliaries should be encouraged further, also from an ecological point of view. The Agency stressed that the advantage of vaccinations would far outweigh any theoretical risks posed by thiomersal3.
Thiomersal has been linked to the occurrence of autism by some scientists, anti-vaccine activists and some parents of autistic children, in particular in the USA. However, a link between thiomersal and autism is considered to have been disproved, from today’s perspective. Meanwhile, the World Health Organization (WHO), the U.S. Institute of Medicine and the European Medicines Agency (EMA) have arrived at the conclusion that all existing studies indicate no such connection independently. Nevertheless, pharmaceutical companies have reacted quickly to the heated debate: mercury-free vaccines are now available for all generally recommended protective vaccinations4.
Thiomersal is still used in medicinal care products for contact lenses. However, AGES has no knowledge of such a manufacturer in Austria. Additionally, there is no information as to whether this substance may be used as a preservative in liquid medicinal products.
The safety of substances containing aluminium has been evaluated for animals. Tests showed that certain amounts resulted in potential damage to the nervous system (mice and rats), male fertility (dogs) and the foetus (mice), as well as in the development of the nervous system (rats and mice). The European Food Safety Agency concluded that the amounts consumers are exposed to via food or consumer products do not represent a risk to human health with respect to questions about potential adverse genome and carcinogenic effects.
The EFSA established a value of 1 mg aluminium/kg bodyweight (Tolerable Weekly Intake, TWI), which can be ingested from various sources on a weekly basis without fear of adverse health effects caused by aluminium, based on existing data and including a high safety factor of 100. In 2008, the EFSA determined the amounts of aluminium that were really contained in the food consumed by different groups in the population. The average population had a weekly aluminium intake of 0.2 – 1.5mg per kg bodyweight, although there were significant regional differences. These exposure data included ingestion via food additives and food contact material, in addition the natural amount of aluminium contained in the food itself. Thus, the TWI value of 1 mg per kg bodyweight was exceeded by a significant portion of the population. The European Commission lowered the amounts permissible for various additives (Regulation (EU) No 380/2012), given the fact that food additives contribute considerably to the aluminium levels of many foods. It is believed that the exposure of the population could be reduced with these measures.
Reports of mutually reinforcing negative effects (so-called synergisms -- i.e. two (toxic) substances ingested at the same time will reinforce their (toxic) effects in a way that the overall effect is much stronger than the sum of the effects of the two individual substances) in relation to thiomersal and aluminium come almost exclusively from one individual or group around this individual, namely Boyd E. Haley, a now retired, former professor at the Chemistry Department of the University of Kentucky, USA, in particular in connection with autism and other neurologic disorders. Haley5 describes an experiment with neurons in a cell culture (in-vitro experiment): aluminium amounts that did not cause significant cell death within six hours were combined with amounts of thiomersal that would only cause a small increase in neuron degeneration on their own. The combination resulted in a 60% increase in the cell death rate, which presented an astounding effect and clear evidence for a synergism, according to the reports published. However, the vulnerable point in these results, which would usually entail further experiments, is that they are only published in biased reports by apparent supporters of a “mercury-autism hypothesis” or journals that have no scientific reputation, and without any details of the experimental process, which in turn can lead to conclusions about the quality of the work performed. The same has to be said about an advocate of the mercury-autism and even Alzheimer’s hypothesis, Donald W. Miller, a surgeon at the University of Washington/Seattle, USA: he presented his opinion in a daily online journal6 without any details or description relating to the actual experimental process: “A small dose of mercury that kills 1 in 100 rats and a dose of aluminum that will kill 1 in 100 rats, when combined have a striking effect: all the rats die. Doses of mercury that have a 1 percent mortality will have a 100 percent mortality rate if some aluminum is there.” This statement is often quoted by supporters of the hypothesis mentioned above, although it has been published without giving any evidence and citations. However, there is another suspect statement which attributes the same toxicity enhancing qualities found in mercury to lead.
We can conclude that no profound and comprehensible study has found evidence for a reinforced negative effect from simultaneous exposure to mercury and aluminium, which exceeds the sum of the individual effects (synergism), to date. A causal link with neurologic diseases, such as autism, is believed to have been disproved with regards to the risk potential of thiomersal, in particular in vaccines and potentially in combination with aluminium compounds. Additionally, legal or consensual actions have been taken to avoid the exposure of children to organic mercury compounds via vaccines in their first few years of their lives.
Nevertheless, mercury can get past the blood-brain barrier and cause toxic effects in the brain. Aluminium is also believed to be able to break this barrier and accumulate in specific brain and neuronal regions. Thus, both metals reach very sensitive areas of the human body. This is why there are programmes in place in the European Union designed to reduce mercury levels in the environment and the exposure of humans, in particular to methylmercury in fish. However, more scientific assays will have to be carried out at the current level of knowledge to keep examining the effect mechanisms and any potential accumulation of the effects relating to both metals.
1European Agency for the Evaluation of Medicinal Products. EMEA Public Statement on Thiomersal Con-taining Medicinal Products. EMEA/20962/99; London, 8 July, 1999 http://www.emea.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003902.pdf
2US Food and Drug Adminstration. Thimerosal in Vaccines. http://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/VaccineSafety/UCM096228
3European Agency for the Evaluation of Medicinal Products. EMEA Public Statement on Thiomersal in Vaccines for Human Use – Recent Evidence Supports Safety of Thiomersal-Containing Vaccines. EMEA/CPMP/VEG/1194/04/Adopted. London, 24 March, 2004
4Robert Koch-Institut. Schutzimpfungen – 20 Einwände und Antworten des Robert Koch-Instituts und des Paul-Ehrlich-Instituts. Stand: 10.05.2007. http://www.rki.de/DE/Content/Infekt/Impfen/Bedeutung/Schutzimpfungen_20_Einwaende.htm
5Haley BE, 2005. Mercury toxicity: Genetic susceptibility and synergistic effects. Medical Veritas 2: 535-542
6Miller DW. Mercury on the Mind. http://www.lewrockwell.com/2004/09/donald-w-miller-jr-md/the-curse-of-mercury-in-vaccines/