While you’ve probably heard of mercury poisoning, especially in relation to ingesting certain foods, you may not have known that mercury is a chemical element that is found all over the earth. It’s only when humans are exposed to this element for too long or at too high of a dose that one can become poisoned by mercury and experience its toxic side effects.
What Is Mercury Poisoning?
Mercury (Hg) is a chemical element found everywhere – rocks, soil, water, etc. – and has an atomic number of 80 on the periodic table of elements. There are various forms of mercury, including elemental, vapor, inorganic, and organic. Some of these forms are more toxic than others.
Humans tend to experience mercury poisoning as a result of a few different ways: inhalation, ingestion, and skin contact. For example, many medical tools and equipment, like a thermometer, contain mercury. If that thermometer breaks, elemental mercury escapes, increasing the risk of poisoning through contact with the skin and inhalation.
Most humans will find themselves most susceptible to mercury poisoning by way of ingestion through the foods they eat.
Mercury Poisoning Symptoms
If you’ve ever heard of the phrase “mad as a hatter,” you may or may not know that this catchphrase is a result of mercury poisoning and its toxic effects on humans. Scientists discovered that the humans who used mercury to process felt hats back in the day often showed signs of mental changes and disturbances as a result of the mercury.
These kind of neurological changes are just some of the symptoms of mercury poisoning. There are some more signs of mercury poisoning you can look out for if you think you may have been or are susceptible to being poisoned. Symptoms vary depending on the type of exposure you’ve had to the element.
Symptoms of Inhalation
Those who have experienced mercury toxicity from inhalation may show signs like:
- Emotional changes like mood swings and irritability
- Problems sleeping (insomnia)
- Headaches
- Muscle twitching or tremors
- Abnormal sensations
- Weakness or muscle atrophy
- Decreased cognitive functions
In some cases, if the exposure is incredibly high, some individuals can experience kidney malfunction, respiratory failure, or death.
Symptoms of Ingestion
For those who experience mercury toxicity through ingestion, symptoms can include:
- Neurological problems
- Hindering of neurological development in the fetus
- Peripheral vision impairment
- Loss of coordination
- Stinging or tingling sensation in extremities and mouth
- Loss of coordination
- Muscle weakness
- Impairments of speech or hearing
- Bloody diarrhea
- Mood swings
- Memory loss
- Renal damage
Pregnant women and developing fetuses are particularly susceptible to mercury poisoning by ingestion, as mercury’s toxic effects can be especially drastic and harmful to the fetus’s brain and neural development.
Symptoms of Skin Contact
Because your skin can absorb mercury, you may experience similar signs of mercury poisoning that you would if you had inhaled it or ingested it. Some visible signs you may notice if your skin comes in contact with mercury are:
- Skin rashes
- Inflammation (dermatitis)
Mercury Poisoning from Fish
Methylmercury, an organic form of mercury, is naturally present in the environment and is also present as a result of industrial pollution. Mercury can damage cells in tissues and cause detrimental effects on the organs.
When mercury enters fish and shellfish tissue, which is the most common way humans ingest mercury, the mercury remains in the tissue; it is not cleared out of the fish and is there when the fish is sold for consumption. The bigger and older the fish is, the higher the concentration of mercury there may be in the fish. This is also true for fish that eat other fish, such as shark and tuna.
People who consume a lot of fish are at risk of mercury poisoning. While one tuna dinner may not poison you, a build-up of mercury in the body can lead to toxic levels that have harmful effects like neurological damage. This is especially true for fetuses and young children who are more susceptible to neurological damage from mercury poisoning.
How Much Fish Can You Safely Eat?
The FDA (Federal Drug Administration) and EPA (Environmental Protection Agency) have issued warnings about how much fish you can safely eat and which fish you should avoid eating.
While their warnings are aimed at pregnant women, women of childbearing age, nursing mothers, and young children, their advice is sound advice for any adult who is concerned about mercury poisoning from fish.
In general, the two groups advise that the following fish be avoided due to their high mercury levels:
- Shark
- Swordfish
- Mackerel
- Tilefish
Instead, fish that is safer to consume due to low mercury levels includes:
- Salmon
- Shrimp
- Pollock
- Catfish
- Light canned tuna
The FDA and EPA recommend eating no more than 12 oz. (340 g) of these safer fish per week, which is about two servings or meals of fish. If you are concerned about the mercury levels present in your locally sold fish and cannot obtain information regarding the mercury content, limit your consumption to 6 oz. a week.
Over time, mercury does eventually leave the body through urine and feces, but keeping mercury levels in the body low is vital to preventing mercury poisoning and experiencing any of its toxic side effects.
Quick FAQ’s
How much tuna causes mercury poisoning?
The EPA recommends that only 1 can of albacore tuna be eaten per week (by someone weighing more than 150 pounds), while the FDA recommends that only 1 can of albacore tuna be eaten every 9 days.
How much mercury is toxic to humans?
Normal whole blood mercury is typically <10 ng/mL. Significant exposure is indicated when the whole blood mercury is >50 ng/mL.
How long does mercury poisoning last?
How long mercury poisoning lasts depends on how long you’ve been exposed to the mercury and how high the levels of mercury in your body are. If you’ve been exposed to mercury for many years, it will take longer to clear it from the body.
