All About Organic Mercury
TLDR: All forms of mercury are toxic to the brain and body once it enters your blood stream. The younger you are the worse the effect, with fetuses being impacted the worst. The impacts are very serious even with allowed exposure levels.
The only treatment I know of is Chelation Therapy, which is very hard to get done voluntarily and only works on body mercury, not the brain.
Here is a great reference for a detailed breakdown of the toxicological impacts [Toxicological Profile for Mercury]
Note: I will be referring to all the forms as just “mercury”, see the mechanism section below for a more detailed breakdown.
Sources of Mercury and how to Avoid Exposure
The simplest answer is for adults to just avoid eating apex predator fish often and steer away from mercury containing vaccines (if any still exist where you live). For pregnant women and children, to outright eliminate all potential sources, even if minor since the effects are magnified in a developing brain.
Mercury gets into the environment primarily through industrial pollution like coal burning where the smoke contains mercury. Other sources like volcanoes, forest fires, and rock weathering also contribute but to a lesser degree.
Fish
The main way people get exposed to mercury via bioaccumulation in apex predators like tuna and swordfish. See the image below for illustration (from wikipedia)
Other fish contain mercury and that should be accounted for, just in lower quantities. See this list from the FDA for the full breakdown [https://www.fda.gov/food/environmental-contaminants-food/mercury-levels-commercial-fish-and-shellfish-1990-2012].
Vaccines
Thiomersal was the primary culprit of mercury exposure via vaccines as a preservative in flu shots. It has been more or less phased out in developed nations since the early 2000s due to it's mercury content and safer alternatives. The amounts were small so the major risk was to pregnant women and infants, just keep an eye out for mercury containing compounds in anything given to pregnant women or children.
Work or other
If you're getting exposed to mercury via vapors or the metal or anything along those lines I assume you know what you're doing, otherwise that's just being dumb. There are safe ways to handle mercury, you can even stick your bare hand (no cuts) into a bucket of pure liquid mercury with basically 0 impact due to the form of the mercury and exposure type.
There are more difficult to catch ways of exposure via contamination of things like cosmetics, but those are a case by case basis and in general not one of the big ones.
Partial Treatment - Chelation Therapy
Chelation Therapy is the only medical intervention I know of that can get rid of mercury from the body. There are a few different drugs that can do this and they can be administered orally or intravenously. The major downside is that it cannot remove mercury from the brain due to the Blood-Brain Barrier.
Mechanism of Action and Why It's So Bad
Disclaimer: This is not a masterful deep dive into the exact science, that would be both much too long and beyond what I know. It is however a solid framework of fundamentals to push past typical surface level understanding and hand waiving.
Key types of Mercury
There are several types of mercury that matter in this context with the two main categories being organic mercury and inorganic mercury.
Organic mercury is mainly Methylmercury and Ethylmercury, both are absorbed very well by the body. Both are extremely to the brain, also body but less so. Methylmercury is the one found in fish like tuna while Ethylmercury is the one found in some vaccines. They are toxic in almost exactly the same way with the differences being how they interact with the blood brain barrier and what they get converted into. Some people try to make an argument of how one type is more dangerous than the other, complete bs, here's one pretty good study on it. Comparison of blood and brain mercury levels…
Inorganic mercury is not really consumed directly but something that forms in the body after consuming organic mercury. Inorganic mercury is still toxic, more so to the body than brain.
Impact on the Brain
Main point is that mercury in the brain accumulates and can make you retarded, no sugar coating.
AI generated textbook summary:
Methylmercury is a potent neurotoxin that readily crosses the blood-brain barrier and placenta, accumulating in the central nervous system (CNS) where fat content is high. This leads to neuronal damage, particularly in developing brains, causing irreversible harm even at low levels. In adults, it disrupts synapse transmission, microtubule assembly, amino acid transport, and cellular migration, resulting in symptoms like memory loss, attention deficits, motor impairments, visual and verbal issues, ataxia (loss of coordination), and paresthesia (tingling sensations). It interferes with neurotransmitter release (e.g., dopamine) by blocking calcium and sodium ion channels, reducing electrical activity in neurons. In fetuses and children, prenatal exposure can cause severe developmental issues, including cerebral palsy, deafness, growth delays, cognitive dysfunction, and decreased intelligence, as the toxin concentrates more in fetal brains than in mothers. Histologically, it leads to loss of cerebellar granule cells and myelin degradation, triggering autoimmune responses against brain proteins. Overall, the brain's vulnerability stems from methylmercury's ability to induce oxidative stress and apoptosis (cell death) in neurons and glial cells, which support brain function.
~ Source [Methylmercury Exposure and Health Effects]
Impact on the Body
Corrosive and toxic, especially to the kidneys which try to filter it out of the blood. Not the end of the world like with the brain, but pretty bad.
AI generated textbook summary:
Methylmercury exerts systemic toxicity beyond the nervous system. It can damage the gastrointestinal tract, kidneys, and immune system due to its corrosive properties and ability to disrupt cellular functions. For instance, high exposure may lead to kidney toxicity by interfering with enzyme activity and causing oxidative stress, which damages cells and tissues. It also promotes lipid peroxidation (the breakdown of fats in cell membranes) and mitochondrial dysfunction, impairing energy production in cells. In the digestive and immune systems, mercury compounds can cause inflammation, reduced immune response, and symptoms like tremors, insomnia, and neuromuscular issues from prolonged exposure. Skin and eye irritation may occur from direct contact with inorganic forms, but methylmercury's fat solubility allows it to penetrate tissues more readily, exacerbating whole-body effects. Long-term low-dose exposure has been linked to cardiovascular risks, such as heart disease promotion
Partial source: [Health Effects of Exposures to Mercury]
Half Life
The half life of Mercury is a big deception point. Might be ignorance but I call it deception since it's obvious to me and I'm not that smart so the people doing the studies and conveying the information must know as well.
It starts out in the digestive system and/or blood. From there the half life is around 2-3 months, but the key here is that this is the half life of mercury in the blood. Around 5-10% of the methylmercury crosses the blood brain barrier, so after 3 months the blood concentration would be half, but the brain is another story. And that's still half life, not complete elimination. Once in the brain, organic mercury last for an extremely long time there practically never getting eliminated, only some of it slowly getting converted to inorganic mercury which is less neurotoxic (still toxic though). Ethylmercury is a bit of a different story, the half life in blood is lower but a larger fraction crosses the blood brain barrier and it has a slightly higher conversion to inorganic form in the brain. Either way we're talking about months of toxicity in the blood and nearly lifelong impacts on the brain from a single exposure.
Additionally what people often overlook is that since the half life is so long mercury exposure is essentially cumulative.
Blood vs Total Mercury
The blood is an intermediary point for mercury absorption, practically all of the guidelines and literature reference blood mercury levels. The justification is that it's the easiest and most concrete one to measure, but that's just plain bad medicine. You can't just change the definition of what is dangerous to suit your detection methods, like a child that covers his face and thinks the world is now dark. The main issue is that this excludes all of the mercury that has been incorporated into the brain and body tissues, where all of the damage happens. Low blood mercury could be either that the total levels in the body are low, or that it's all moved into the brain, there's no way to tell which it is.
Now this would be a fair argument because the idea is that mercury becomes problematic in the short term when your blood levels are high because that means there's so much that it's still showing up in your blood. This is valid but only in the short term and under an acceptable dose of mercury framework. Long term this falls apart completely since brain mercury is undetectable in blood.
Fetus, Infants, and Autism
I put the fetus and infant in its own category to illustrate how sinister and serious it is. Two key aspects come into play. The first is that the mothers body actively diverts organic mercury compounds into the placenta since it mimics healthy compounds. The second is that a developing brain (fetus) is orders of magnitude more sensitive to mercury than an adult brain. These two factors combine to create what is almost an unbelievably sinister combination. What can start off as a relatively small amount of mercury can turn into almost a targeted strike on the fetus brain. Here is where thimerosal (ethyl mercury) and canned tuna (methyl mercury) differ in their impacts but regardless, both are bad and anyway both have already been recommended against for pregnant women.
Autism comes into play here because even the most liberal minded people acknowledge the fact that autism rates have risen significantly, beyond what can be explained away by detection methods and similar factors. I think I've laid out enough of my own opinions on the matter so I will defer to an extract from this paper. [Comparison of Blood and Brain Mercury Levels in Infant Monkeys…]
Stereologic and autometallographic studies on the brains of these adult monkeys indicated that the persistence of inorganic Hg in the brain was associated with a significant increase in the number of microglia in the brain, whereas the number of astrocytes declined. Notably, these effects were observed 6 months after exposure to MeHg ended, when inorganic Hg concentrations were at their highest levels, or in animals solely exposed to inorganic Hg (Charleston et al. 1994, 1995, 1996). The effects in the adult macaques were associated with brain inorganic Hg levels approximately five times higher than those observed in the present group of infant macaques. The longer-term effects (> 6 months) of inorganic Hg in the brain have not been examined. In addition, whether similar effects are observed at lower levels in the developing brain is not known. It is important to note that “an active neuroinflammatory process” has been demonstrated in brains of autistic patients, including a marked activation of microglia (Vargas et al. 2005).
Significance with Concrete example
BBQ chicken gets classified as a carcinogen because of the char. We need to put numbers and concrete examples behind these ideas to get an idea of how bad it actually is.
Scenario 1: Man eating canned tuna
Setup:
- 3x ~150g can of Albacore canned tuna per week, very reasonable for some people.
- Light canned tuna is ~0.125ppm methylmercury per can, albacore is ~0.35ppm. A can has roughly 100g of fish (minus water and oil) so that's around 35µg
- 70kg male with ~5L of blood
- Roughly the targets for exposure for adult men are:
- <5µg/L (<25µg) : little to nothing
- 5-20µg/L (25-100µg) : Mild exposure
- 20-50µg/L (100-250µg) : Problematic, needs clinical attention
- >100µg/L (>500µg): Poisoning / acute effects.
Result:
That gets our man to ~100µg of methylmercury in week 1 since almost all of it is absorbed. At the end of week 2 he has around ~85µg from week 1 + a bit less than 100µg from week 2, that puts him at ~180µg. Keep going and the guy is screwed.
Now you'll hear the argument of how this is total mercury and there won't be all 100μg in the blood at a single moment, but that's just a measurement trick. The body absorbs mercury pretty quickly so there usually won't be all 100μg in the blood at once, but you definitely did consume all 100μg and it is in your body, just has already started going into your brain, kidneys and other tissues.