Taking a break from coronavirus coverage, I want to highlight an important change by the EPA that may reduce regulation of mercury emissions from power plants. This can have serious ramifications for our health and our environment. Mercury poisoning can be serious, and I want to provide a timely review of mercury exposure and health effects given these changes.
As I wrote in my complete guide to indoor air quality, our environment is a critical part of our health!
Wait – I thought we get mercury poisoning from thermometers and fish. Why do power plants matter?
The largest source of mercury is as an incineration byproduct from coal-fired power plant emissions. It then accumulates in the environment, such as in fish, and in land animals that eat fish, including birds and bears.
What Does Mercury Poisoning Look Like?
Mercury is a body-wide toxin affecting many organs:
- Nervous system: personality and memory changes, tremors, and auditory and visual changes.
- In children: development delay (walking, talking, coordination, learning or speaking disability, seizures). Behavioral changes, problem solving difficulties.
- Kidneys: since they filter all our blood they accumulate mercury and become damaged.
- Heart: rhythm changes, increased blood pressure.
- Irritation of mouth, lungs, stomach (burning, coughing, nausea, vomiting, diarrhea).
- Reproductive and immune system harm.
This is a wide range because it appears to depend on the load of mercury poisoning.
Mercury Poisoning and the “Mad Hatter”?
“Mad hatter’s” disease describes the psychosis and other psychiatric symptoms of hat makers from occupational exposure in the early 20th century. This is just an example of how varied mercury poisoning symptoms can be.
Pregnant women and children are at higher risk of mercury poisoning
The developing fetus and child are at higher risk because of susceptible organs, particularly the immature brain.
- Pregnant women can pass mercury to the fetus through the placenta.
- Asian women, in particular, appear to be at higher risk of higher mercury levels.
- Mercury can also pass through breast milk into infants.
These high risk groups should limit high mercury loads from shark and swordfish.
What are the Types of Mercury That Lead to Mercury Poisoning?
Mercury enters our body through:
- Inhalation (as odorless vapor).
- Swallowing (in food).
- Skin contact
Mercury exists in our environment in three forms:
- Metallic mercury (AKA elemental mercury): shiny liquid that we inhale vapors from.
- Methylmercury: predominant form in fish that we consume. This form is most commonly associated with developmental defects in children.
- Inorganic mercury salts: used as fungicides and in skin-lightening creams.
Each of these forms acts differently, and I’ve posted a thorough review at the very end of this post if you’re interested!
Major Mercury Exposure Sources
- Food: fish, wild game, marine mammals (as methylmercury).
- Any animals that eat fish that humans subsequently consume. For example, some chickens are fed fish feed.
- Until the 1970’s methylmercury was used as a fungicide on grains and seeds.
- Paint: fortunately banned in the 1990’s because of the toxic vapors.
- Industrial exposures: work with thermometers, barometers, fluorescent light manufacturing, or chlor-alkali industry.
- Breast milk.
Mercury and Fish (and other animals)
Mercury bioaccumulates in the food chain. Importantly, other toxins do, too. Hence larger fish with long lifespans that eat smaller fish (like shark and swordfish) have high mercury loads.
Furthermore, animals that eat fish also bioaccumulate mercury. This happens in nature (bears) and on farms (chickens fed fish feed).
What About Canned Fish?
Canned fish does not necessarily have increased mercury. However, the can linings may leach harmful plastics into the food. Other contaminants from the manufacturing process may also leach into the food. Whenever possible, I recommend patients to eat whole foods with minimal processing and packaging. Ingredient labels won’t necessarily tell you the mercury load or other toxic load from the can or its lining.
Farmed vs Wild Caught Fish
Mercury bioaccumulation occurs in both farmed and fresh fish. Farmed fish has other considerations though, including:
- Disease from farming conditions.
- Industrial pollutants that preferentially end up in smaller bodies of water before entering the ocean.
Given the above, I recommend wild caught fish whenever possible.
Other Sources of Mercury Poisoning
There are many other non-fish sources of mercury that we need to watch out for!
- Dental amalgam fillings (~50% mercury). Exposure depends on many factors that increase mercury release over time:
- Number of amalgams.
- Grinding teeth.
- Chewing gum.
- Spills from thermometers, electrical switches, fluorescent light bulbs.
- The spillage must immediately be sealed air-tight to prevent inhaling the toxic vapors.
- Medications and skin-lightening creams. Keep out of reach of children!
- Marine animal meat (whales, dolphins, walruses, seals).
- Plants contain very little mercury.
- Mushrooms grown in mercury-contaminated soil.
- Traditional medicinal remedies (in some Chinese and Hispanic cultures).
- Carried into the home from clothes and shoes contaminated at work. Mercury is very difficult to remove from clothing and this exposure can pass to children!
What do you do if You’ve Spilled Metallic Mercury to Avoid Mercury Poisoning?
You need not panic, but act quickly to prevent inhalation of vapors, particularly by children:
- Don’t vacuum: this can form more mercury vapor!
- Don’t step on it because it can track around the home.
- Don’t try to wipe it or soak it because mercury won’t be absorbed! You’ll simply spread it more.
- Use paper to roll the beads onto a second sheet of paper, or
- Use an eye dropper to suck up the beads.
- Place beads in an airtight container and dispose of safely.
- Ventilate the room with outside air for at least 1 hour and close the room off from the rest of the home.
- Remove children from area.
- If spilled on carpet, try above and contact local health department. Don’t vacuum!
Can I Test for Mercury Poisoning?
Testing can be from blood, urine, hair, breath, or breast milk. The choice depends on the suspected exposure type and timing. Hair can reveal methylmercury exposure, and, depending on hair length, you can try to determine the timing.
If interested in the other tests, more information is at the very end!
Regulation of Mercury and Other Toxins
We should all be concerned by any actions to reduce pollution regulation.
No one thinks more methylmercury in the environment would be a positive.Elsie Sunderland, Harvard University
Also, it is important to remember that mercury does not bioaccumulate independently of other toxins. Dioxins are but an example of environmental pollutants that accumulate in the food chain similarly to mercury.
Furthermore, mercury exposure also depends on climate change by directly affecting methylmercury levels in fish. Our environment’s health is deeply connected to our health, and we need to protect our environment as if we are protecting ourselves and our children. I leave you with this powerful Native American saying:
We do not inherit the earth from our ancestors, we borrow it from our children.Native American Proverb
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The information provided in this post in intended for general education. It is not medical advice. While I make every effort to provide the most up-to-date information, please note that new data is continuously becoming available and may change the conclusions I present here.
The different types of mercury in our environment and how they enter our bodies
Let’s take a step back to understand the types of mercury and how they enter our body:
- Metallic mercury (AKA elemental mercury): shiny liquid at room temperature.
- We inhale vapors that enter the brain and placenta. Not readily absorbed if swallowed.
- Can persist in body for weeks-months, Possibly longer in the brain (gets converted to inorganic form and gets “trapped” in brain). Accumulates in kidney and brain.
- Exits body in urine, feces, and exhaled breath.
- Methylmercury: predominant form in fish.
- We primarily swallow this form (95% absorption). Poor skin absorption. Minimal vapor and hence low inhalation exposure.
- Can enter brain, placenta, and breast milk.
- Persists in body for months, possibly longer in brain (gets converted to inorganic form and gets “trapped” in brain).
- Inorganic mercury salts: used as fungicides and in skin-lightening creams.
- Not absorbed as easily as metallic or methylmercury. Doesn’t form vapor to inhale.
- Enters brain and placenta less but can contaminate breast milk. Doesn’t vaporize at room temperature (like elemental mercury).
- Persists in body for weeks to months, accumulating in kidneys.
The different ways to test for mercury exposure
- Urine: can identify metallic mercury vapor and inorganic mercury exposure.
- Not useful for determining methylmercury exposure.
- Urine mercury levels fall relatively quickly after exposure and are not useful for detecting long term exposure.
- Blood: can identify multiple types of mercury exposure.
- Blood must be sampled after recent exposure because blood levels decrease within days. Hence blood is not as useful for long term exposure.
- Hair: useful for methylmercury. Specifically, depending on how long the hair is, you can determine when the exposure occurred.
- Breath: can detect recent metallic mercury exposure.