Mercury poisoning refers to a toxicity from mercury consumption. Mercury is a type of toxic metal that comes in different forms within the environment. The most common cause of mercury poisoning is from consuming too much methylmercury, which is linked to eating seafood.

Small amounts of mercury are present in everyday foods and products, which may not affect your health. Too much mercury, however, can be poisonous. Mercury itself is naturally occurring, but the amounts in the environment have been on the rise from industrialization. The metal can make its way into soil and water, and eventually to animals like fish.

Consuming foods with mercury is the most common cause of this type of poisoning. Children and unborn babies are the most vulnerable to the effects of mercury poisoning. You can help prevent toxicity by limiting your exposure to this potentially dangerous metal.

Methylmercury is most notable for its neurological effects. In general, the U.S. Food and Drug Administration says that too much mercury can cause:

More often, mercury poisoning builds up over time. However, a sudden onset of any of these symptoms could be a sign of acute toxicity. Call your doctor right away if you suspect mercury poisoning.

Mercury poisoning symptoms in adults

Adults with advanced mercury poisoning might experience:

  • hearing and speech difficulties
  • lack of coordination
  • muscle weakness
  • nerve loss in hands and face
  • trouble walking
  • vision changes

Mercury poisoning symptoms in children and infants

Mercury poisoning can also disrupt fetal and early childhood development. Infants and young children who’ve been exposed to high levels of mercury may have delays in:

  • cognition
  • fine motor skills
  • speech and language development
  • visual-spatial awareness

High amounts of mercury can lead to long-term and sometimes permanent neurological changes. The dangers are especially notable in young children who are still developing. Mercury exposure can lead to developmental problems in the brain, which can also affect physical functions such as motor skills. Some children who are exposed to mercury at a young age may develop learning disabilities, according to the Environmental Defense Fund.

Adults with mercury poisoning may have permanent brain and kidney damage. Circulatory failure is another possible type of complication.

Mercury poisoning from fish

Methylmercury poisoning is largely linked to eating seafood, mainly fish. Toxicity from fish has two causes: eating certain types of mercury-containing fish and eating too much fish.

Fish get mercury from the water they live in. All types of fish contain some amount of mercury. Larger types of fish can have higher amounts of mercury because they prey on other fish that have mercury too. Sharks and swordfish are among the most common of these. Bigeye tuna, marlin, and king mackerel also contain high levels of mercury.

It’s also possible to develop mercury poisoning from eating too much seafood. In small amounts, the following types of fish are okay to eat once or twice per week:

  • albacore tuna
  • anchovies
  • catfish
  • grouper
  • pollock
  • salmon
  • shrimp
  • snapper

Though these options contain less mercury overall, you’ll want to take care in how much you eat.

If you’re pregnant, the March of Dimes recommends eating no more than 6 ounces of tuna per week and 8 to 12 ounces of other types of fish. This will reduce the risk of fetal mercury exposure. You’ll also want to watch your fish consumption if you’re nursing, as mercury can also be passed through breast milk.

Read more: The 11 best types of fish to eat »

Other causes of mercury poisoning can be environmental or from exposure to other forms of the metal. These include:

  • broken fever thermometers
  • “silver” dental fillings
  • certain types of jewelry
  • mining for gold
  • skin care products (Those made in the United States don’t usually contain mercury.)
  • exposure to toxic air in industrialized communities

Harmful toxins in cosmetics: What to avoid »

Mercury poisoning is diagnosed with a physical exam and a blood test. Your doctor will ask about your symptoms and when they started. They will also ask you about your dietary choices and other lifestyle habits.

A blood mercury test is used to measure levels in your body.

There is no cure for mercury poisoning. The best way to treat mercury poisoning is to stop your exposure to the metal. If you eat a lot of mercury-containing seafood, stop immediately. If toxicity is linked to your environment or workplace, you might need to take steps to remove yourself from the area to prevent further effects of poisoning.

If your mercury levels reach a certain point, your doctor will have you do chelation therapy. Chelating agents are drugs that remove the metal from your organs and help your body dispose of them.

Long term, you may need continuing treatment to manage the effects of mercury poisoning, such as neurological effects.

When detected early, mercury poisoning can be halted. Neurological effects from mercury toxicity are often permanent. If you suspect sudden mercury poisoning, call the Poison Control Center at 800-222-1222.

The best way to prevent dietary mercury poisoning is to take care with the amounts and types of seafood that you eat. You can also:

  • Eat larger types of fish on an occasional basis.
  • Avoid fish containing high levels of mercury if you’re pregnant.
  • Follow fish and seafood serving guidelines for children. According to the Mayo Clinic, children younger than 3 years old can eat 1 ounce of fish, while a serving size for children ages 4 to 7 is 2 ounces.
  • Be choosy with your sushi choices. Many popular sushi rolls are made with mercury-containing fish.
  • Be on the lookout for fish advisories in your area. This is especially useful if you fish for your own seafood.
  • Take a blood mercury test before conceiving.
  • Wash your hands right away if you think you’ve been exposed to other forms of mercury.