Tag Archives: Thimerosal

An Exploration of Thimerosal Toxicity and the Autistic Brain: Part I

In their paper, “Thimerosal Exposure and the Role of Sulfation Chemistry and Thiol Availability with Thimerosal,” Janet Kern, Boyd Haley, David Geier, Lisa Sykes, Paul King and Mark Geier explore recent studies that suggest children with the autism spectrum disorder(ASD) have physical biomarkers for the disorder:  abnormal levels of sulfation chemistry, limited thiol ability, and lower levels of glutathione (GSH—a type of thiol) that lead to weaker oxidation capacities and detoxification. Specifically, Kern et al. discuss the extent to which the hypothesis that GSH and sulfation chemistry impact how the body reacts to Thimerosal, a mercury-containing compound that was used as a preservative in many standard childhood vaccines in the United States and around the world. Kern wondered: could a combination of abnormal sulfation chemistry, lower GSH, and limited thiol ability make an individual’s susceptibility to the toxic effects of Thimerosal greater?


While many characterize autism as a psychological/behavioral disorder, some researchers, including Mark and David Geier, have shown that ASD individuals also demonstrate physical abnormalities. These physical symptoms include seizures, sleep disorders, gastrointestinal issues, and incontinence, among others. The presence of physical symptoms suggests that there should be metabolic biomarkers for ASD, given that it is in fact a disorder with symptoms beyond abnormal neurodevelopment.

We also know that autism can be a regressive disorder, in which individuals aren’t born as autistic, but rather only begin to display symptoms of ASD after 15-24 months of age. Research offers widely varying rates for the frequency of autistic regression, but the lowest frequency reported among populations of ASD sample studies has been 15% to more than half of all cases. To determine how a potential environmental factor like Thimerosal could affect ASD, Kern et al. looked specifically at ASD individuals with regressive autism.

A Word on Thimerosal

Even though Thimerosal began to be phased out of some common childhood vaccines around 2000, at the same time, the CDC began to encourage pregnant women in their 2nd and 3rd trimesters, and infants as early as 6 months, to receive flu vaccines, vaccines which were still preserved with Thimerosal. Today, more than half of all flu vaccines are preserved in Thimerosal.  Thimerosal is not found in nature, and its toxicity has been proven in many studies; in fact, it’s the most toxic non-radioactive metal to fetal and neuronal cells.

GSH, Thiols and Sulfation

Let’s return to Thimerosal’s connection to thiols and GSH. Thiols are known to mitigate the toxicity of Hg, and in turn, the toxicity of Thimerosal; studies have shown that the extent of Thimerosal’s toxicity to the body is largely dependent upon the cellular content of the GSH thiol. The degree of cell damage after Thimerosal exposure is highly dependent upon the availability of these thiols; yet paradoxically, Thimerosal decreases their production and effectiveness when introduced. Studies have shown that GSH levels in mice not only decreased after exposure to Thimerosal, but persisted at low levels for weeks after exposure. Exposure to mercury (the toxic element of Thimerosal) has also been shown to hinder the development of the brain’s GSH antioxidant system, which can cause oxidative damage.

It’s also been demonstrated that individuals with ASD have unusual sulfation chemistry, to the extent that researchers believe it’s the result of either faulty sulfate production or use that exceeds the body’s rate of replenishment.  Specifically, ASD individuals maintain approximately 50 times the sulfite levels of control children. It’s important to note here that sulfite is an extremely toxic compound that, in a properly functioning body, is converted to the non-toxic compound sulfate. As Kern et al. point out, studies have shown that Hg has the potential to interrupt this conversion process, and thus result in higher levels of toxic sulfite in the body. In fact, children with abnormal transulfuration (a term used to describe this conversion process) also are found to have lower levels of accompanying transulfuration metabolites. Interestingly, the majority of children with these levels developed autism after 15 months of age, suggesting their autism is regressive.

Researchers have also discovered that the lower an individual’s sulfate levels, the more severe the nature of their autism; this was also found to be the case with GSH levels. In other words, these biomarkers play a role in the manifestation of autistic symptoms. Should they be limited, by something like Hg, which is known to affect both GSH and sulfation, research suggests the severity of autistic symptoms increases.  All of the relationships Kern et al. have analyzed between Thimerosal and GSH/sulfation lay the framework, as detailed in the second half of the blog, for a compelling argument for Thimerosal’s ability to affect some ASD children more severely than others.