Mercury is a highly toxic heavy metal that can have devastating effects on human health.
Despite being a toxin, mercury is used industrially in the manufacture of electronic devices, paints, and fungicides, as well as in waste incineration (Tinggi 2022).
Mercury toxicity varies with the type and dose of exposure, though it is primarily associated with the outgassing of mercury from dental amalgams, consumption of contaminated seafood, coal-burning power plants, mining, industrial contamination, volcanic activity, accidental spills, or occupational exposure. Metallic mercury can be deposited in the brain, thyroid, breast, heart, muscle, adrenal glands, liver, kidney, skin, sweat glands, pancreas, enterocytes, lungs, salivary glands, testes, prostate, placenta, and fetal tissue (Bernhoft 2012).
Assessing mercury status can be complex as notable inter-individual variability can occur regarding blood, urine, hair, and other tissue levels following a given exposure (Branco 2017).
Although not conclusive, some blood chemistry changes may be associated with mercury exposure and should be explored further, including
Mercury toxicity may be associated with:
Recent mercury exposure can be evaluated by measuring blood, hair, and urine levels, though these do not correlate well with total body burden. Also, symptoms may occur despite low mercury levels. Chronic low-grade mercury may not be easily detected but can be associated with weakness, fatigue, anxiety, depression, odd paresthesias, anorexia, weight loss, gastrointestinal disturbances, memory loss, and difficulty concentrating (Bernhoft 2012).
Urine levels of mercury (Hg) provide the most appropriate assessment of elemental mercury exposure and are useful for the assessment of acute and chronic exposures. A 24-hour urine specimen collected in an acid-washed plastic container is the preferred specimen. A first-morning void can provide a close approximation of the urine (using specific gravity or amount of creatinine present).
A urinary mercury concentration of less than 2 micrograms per liter (μg/L) (the 95th percentile for adults) would be considered within the background range.
Mercury has a short half-life in blood (3 days), so blood analysis may be performed during the first 3 days after an acute high-level exposure. Interpretation of blood Hg levels may be complicated by dietary sources of mercury.
Blood samples should be collected in vacutainers containing heparin and then refrigerated.
The blood Hg level for the 95th percentile of the U.S. population is below 5 micrograms per liter (μg/L); a blood concentration of 50 μg/L or greater is considered the threshold for symptoms of toxicity.
Some individuals with high blood mercury levels may not exhibit clinical symptoms. Hair analysis primarily measures organic (methyl) mercury exposure only and is not useful for assessing recent exposures.
Source: CDC. Agency for Toxic Substances and Disease Registry (ATSDR). Evaluating Mercury Exposure: Information for Health Care Providers. October 4, 2018. https://www.atsdr.cdc.gov/dontmesswithmercury/pdfs/info-for-health-care-providers.pdf
If mercury overload is confirmed, decontamination should be undertaken and chelation initiated as early as possible to minimize toxic effects. A qualified healthcare practitioner may help facilitate removal using the chelator DMPS for most cases or DMSA for organic mercury (Bernhoft 2012).
Adequate selenium intake may help mitigate mercury toxicity. Primary food sources include Brazil nuts, seeds, mushrooms, fish, seafood, beef, and poultry (Nessel 2023). Selenium content can vary depending on the selenium content of the soil in which foods are grown or grazed. Notable selenium sources include (Tinggi 2022):
|
Food |
Selenium Level (µg/kg) |
Country |
| Milk and dairy products | ||
| Milk | 10.7–16.2 | Greece |
| Milk | 10.0–14.0 | Switzerland |
| Milk | 60.0 | Korea |
| Milk | 22.5–25.9 | Australia |
| Cheese | 24.1–95.4 | Greece |
| Cheese | 70.0–78.9 | Australia |
| Meat and eggs | ||
| Beef | 33.5–6.31 | Greece |
| Beef | 67 ± 23 | Switzerland |
| Beef | 324 | Korea |
| Lamb | 80 | Switzerland |
| Chicken | 76.3–82.4 | Greece |
| Chicken | 114 ± 17 | Switzerland |
| Pork | 90.0–98.2 | Greece |
| Pork | 115 ± 75 | Switzerland |
| Pork | 174–199 | Korea |
| Eggs | 56.4–181.1 | Greece |
| Eggs | 190–414 | Australia |
| Cereals | ||
| Bread | 37.9–150.2 | Greece |
| Bread | 23–48 | Switzerland |
In the United States, the estimated average requirement for selenium for non-pregnant, non-lactating adults is 45 micrograms/day, the RDA is 55 micrograms/day, and the tolerable upper intake level is 400 micrograms/day (Nessel 2023).
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