Mercury has different forms, and people get exposed to it in a variety of ways. Eating fish that contains methylmercury is the most common culprit of mercury poisoning in America, but there are also other carriers of mercury, such as a mercury thermometer that, when broken, emits elemental mercury into the air. And coal-burning power plants release the highest amount of mercury into the air. If you think you have mercury exposure, we recommend that you contact your doctor, who will investigate further to understand the degree of exposure and how to handle the situation.
People can get exposed to three forms of mercury:
- Elemental (metallic) mercury
- Other mercury compounds
Methylmercury is a toxic organic compound, and it is the most common form of mercury exposure. Our bodies might carry traces of methylmercury, but this trace amount does not affect our health.
The danger lies in eating fish and shellfish that are high in methylmercury. The mercury in fish can indeed have effects on our bodies. But how does methylmercury get into the fish and shellfish?
Mercury vapor infiltrates the air, and when it moves into the water, microorganisms transform it into methylmercury—in this way, it enters fish and shellfish.
Levels of methylmercury in seafood depend on what the fish eat, as well as where they fall in the food chain. The large predatory fish typically house the highest concentrations of methylmercury.
Experts recommend that you eat fish with low levels of mercury, such as:
If you are pregnant or breastfeeding, it is especially important to avoid eating fish high in mercury. Even with no symptoms as a warning, mothers exposed to high levels of mercury have given birth to infants with debilitating health conditions. The route of exposure is through the umbilical cord, and also through breast milk.
Monterey Bay Aquarium’s Seafood Watch is a terrific resource for checking which fish from which waters are the safest to eat.
Elemental Mercury Exposure
Although regulations have tightened, elemental mercury can still be found in older types of batteries, electronic devices, light switches, thermostats, and washing machines. When these products break, they release elemental mercury vapor in the air that's toxic and easily inhaled, especially in warm and poorly ventilated environments.
Fluorescent lightbulbs and LCD TVs still contain mercury, but are safe unless they crack or shatter.
Mercury is also used in dentistry in dental amalgam, a dental filling material used to restore teeth. This 2016 study provides evidence that amalgam fillings can elevate levels of mercury in the body.
Here's an EPA list of products that are sources of mercury.
Other Mercury Compounds
Other compounds of mercury, such as phenylmercury acetate and ethylmercury, have been used as fungicides, antiseptics, and preservatives, but their use is pretty much discontinued today, although some are still used in small amounts as preservatives in vaccines. FDA-approved thimerosal, for instance, is used to prevent microbial growths in American vaccines designed for children 6 years old or younger, but the FDA maintains that levels are too low to cause health problems.
These mercury compounds have not been discontinued throughout the world, and can show up in skincare products from other countries and sold illegally in the United States.
Mercury Poisoning Symptoms
The health effects of mercury exposure manifest according to the type of mercury, the amount of mercury, the length of exposure, the mechanism of exposure, and the age and health of the exposed at the time of exposure. The effects of mercury exposure may not be at all noticeable, or could range in severity from mild to severe.
High blood mercury levels can lead to neurological symptoms such as:
Higher levels of mercury exposure may appear as symptoms such as:
- Muscle weakness
- A metallic taste
- Stomach upset or nausea
- Motor skill impairment
- Breathing, vision, hearing, or speech difficulties
Young children with high exposure might have:
- Poor motor skills
- Challenges with thinking and speaking
- Hand-eye coordination issues
- A lack of overall awareness
Research has yet to find a definitive link between mercury exposure and cancer, but extremely high doses of certain forms of mercury have encouraged the proliferation of cancerous tumors in rats and mice. Still, the EPA has concluded that mercury exposure is unlikely to cause cancer in humans.
Effects of Mercury on the Body
Exposure to methylmercury from eating high levels in seafood can result in symptoms such as:
- Peripheral vision loss
- Tingling in hands and feet
- Trouble with balance and coordination
- Difficulty speaking, hearing, walking
Exposure to methylmercury in the womb can lead to defects in the nervous system that impair cognitive processing, including memory, fine motor skills, attention, language, and visual-spatial skills.
Metallic mercury exposure breathed in as a vapor can cause the following symptoms:
- Heightened or unbalanced emotions
- Trouble sleeping
- Neuromuscular changes
- Impairments to sensations
- Alterations in nerve responses
- Poor mental function
Extreme cases of higher exposure can have life-threatening consequences such as kidney dysfunction and respiratory failure. Other complications cited include high blood pressure and the development of endometriosis, although these are more empirical symptom reports that have yet to be validated by research.
Inorganic mercury compounds can also cause:
- Damage to the gastrointestinal tract
- Damage to the nervous system
- Damage to the kidneys
- Skin rashes and dermatitis
- Memory loss
- Mental disturbances
What to Do About Mercury Poisoning
If you have concerns about mercury exposure, such as from a broken thermometer, call your health care provider or the poison control center at 1-800-222-1222. Follow these tips to minimize the effects of mercury exposure, reduce your long-term exposure, and cleanse your body.
If you are aware of an increased risk of mercury, for instance, if you work at a hospital and elemental mercury is spilled from a product, then remove yourself from the exposure immediately. For example, if a fluorescent bulb ruptures, the U.S. Environmental Protection Agency states to evacuate immediately and let the room air out for a minimum of 15 minutes.
Likewise reduce your exposure to seafood high in methylmercury. The most mercury-rich fish include tilefish, swordfish, shark, king mackerel, and bigeye tuna. Swap them out for mercury-free protein options such as beef and poultry.
What fish takes home the prize for mercury exposure? Everyone's favorite: tuna, especially as it pertains to mercury exposure in the United States. Lower your exposure by eating light or skipjack tuna limited to no more than two servings weekly. Children should reduce their consumption to 12 ounces a week of canned light tuna and 6 ounces per week of canned albacore tuna, and pregnant women should cap tuna consumption at 4 ounces of albacore each week.
A good general rule regarding fish consumption is that the bigger predators contain the highest mercury levels, so go for the smaller fish in the sea. You have many choices, including protein-packed and omega-3-rich fish such as salmon, sardines, and anchovies.
If fish is your main source of protein, lowering your consumption may make it difficult to get all the essential amino acids (EAAs) your body needs to thrive. You can supplement with a daily EAA formula.
A heavy metal detox can help detoxify your body of mercury and other toxic substances. Plan your meals around:
- Vitamin C-rich foods
- Green leafy vegetables
Chlorella, as tablets or in powder form, is a supplement touted for its heavy metal detoxification properties.
Chelation therapy, developed in the 1950s as a cure for heavy metal poisoning, is another option to cleanse your body of mercury toxicity. EDTA, a chelation chemical, is introduced to the bloodstream via injection, where it then connects to excess minerals and ushers them out of the body, thereby removing toxins.
Help Your Bowels
Regular bowel movements are key to ensuring the mercury gets out of your system instead of reabsorbed. Eating a high-fiber diet, drinking plenty of water, and exercising regularly can keep constipation at bay and the detoxification process on track.
A 2012 study showed that probiotics can encourage heavy metal detoxification. According to the researchers, the species of good bacteria known as Lactobacillus can help the detoxification process by binding to chemicals such as mercury and ridding them from the body. You can find Lactobacillus in fermented foods such as yogurt, kefir, and kimchi.
Are You Affected by Mercury Exposure?
Let's take a look at the statistics on file.
Using the National Health and Nutrition Examination Survey (NHANES) during 2003–2004, the Centers for Disease Control and Prevention (CDC) measured the total blood mercury of 8,373 participants aged 1 year and older and mercury levels in the urine of 2,538 participants aged 6 years and older.
Mercury in the blood registers levels of methylmercury, while urine mercury measures exposure to inorganic mercury exposure. Using these assessments, scientists determined the amount of mercury exposure and found that most participants had calculable levels of mercury in their bodies and that levels increase with age. However, that doesn't mean these measurable mercury levels are high enough to have a serious health impact.
Scientists are continually conducting biomonitoring studies on mercury levels to determine reference values that can help physicians and public health officials ascertain mercury exposure and its health effects.