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Frequently Asked Questions About Mercury

Jane M. Hightower, M.D., is a board certified internal medicine physician in San Francisco, California. She published a landmark study that brought the issue of mercury in seafood to national attention. She continues to publish scientific papers and give lectures on the subject. She is the author of Diagnosis: Mercury.

Dr. Hightower recently spoke to Earthjustice supporters and answered some commonly asked questions about mercury in our food supply.

1. How much fish can I eat each week?

That depends on your weight, and the amount of mercury in the fish. For instance, according to the FDA standards, if you weigh 130 pounds, you should eat no more than 4 ounces of fish typically medium high in mercury (tuna, halibut, grouper, northern pike, bass) a week. If you weigh 170 pounds, then you can eat as much as 5.3 ounce a week. Keep in mind, this presumes you don’t eat any other seafood during the week. For the higher mercury fish such as swordfish, tile fish, king mackerel, and shark, you should not eat these at all if you are planning a pregnancy, are pregnant, nursing, or are a young child/infant. For the rest of the population, these fish should not be consumed more than once per month.

2. Do I need to get tested for mercury? How can I get myself tested for mercury levels in my body?

You need to get tested if you are experiencing the symptoms of mercury poisoning, or are a frequent consumer of fish that could put you at risk for adverse effects from mercury (see question 5) or if you have an occupational exposure to mercury. Ask your doctor about getting tested.

3. What are the ways that mercury gets into my body?

Mercury enters your body three ways: breathing (the emissions from coal-fired power plants); absorption through the skin (some cosmetics) and by eating contaminated food and drinking contaminated water. Very small amounts can also come from mercury/silver dental amalgam.

Mercury from coal burning power plants is both a global and local issue. Although a portion of the emissions reaches high in the atmosphere and gets distributed far and wide, it also contaminates locally.

4. Do I need to worry about eating other things (i.e. root vegetables, lettuce, poultry, etc.)?

Fish is the main food to worry about. High fructose corn syrup has been found to have measurable levels of mercury. Limiting processed foods is advisable for sensitive individuals.

5. What are the most common symptoms of mercury poisoning and how do I know when to see a doctor?

There are many non-specific symptoms that have been reported to occur with mercury exposure, but the most common are: fatigue, headache, memory loss, trouble performing complex tasks, depressed mood, metallic taste in your mouth, joint or muscle pain, gastrointestinal upset, chest pain or palpitations, dizziness or faintness and insomnia. If you experience a combination of these, you should discuss the symptoms with your doctor. Please note these symptoms may occur and may indicate an illness unrelated to mercury poisoning.

6. For years, dentists and health advocacy groups have argued whether mercury/silver amalgams were safe for all. I read that the FDA finally admitted that mercury fillings can lead to health problem for some individuals. Why the sudden change?

A number of consumer advocacy groups sued the FDA for the elimination of mercury in fillings. As part of the settlement reached in 2008, the FDA agreed to identify potential risks of mercury fillings and issued a statement saying metal dental fillings may lead to health problems in pregnant and nursing women, small children and people with compromised immune systems.

7. Do I need to have mercury fillings removed?

It’s generally not necessary to remove your mercury fillings. The use of mercury-based fillings has declined to about 30% of all fillings in the U.S. Other countries have eliminated their use completely. If you are seeing your dentist for a routine filling, or replacement of old fillings, ask if he or she uses non-mercury based fillings.

8. Compact fluorescent lights (CFLs) have about 4,000 mcg of mercury in them. Should I be worried about using these types of light bulbs?

Most of the mercury inside is bound to the bulb during use and cannot escape. Be careful when installing or replacing a CFL, as it could break. All CFLs should be recycled and not be thrown in the garbage. You can return these bulbs to the place where you bought them. If you break a bulb and mercury escapes, call your hazardous waste person or local fire department for directions on decontaminating the spill area.

9. In your book, Diagnosis Mercury, you write about "Feeling the heat in mercury politics." Why has there been such a backlash on regulating mercury pollution?

Wherever mercury has been, there has been an incredible amount of money to be made or lost. Coal fired power plants are currently the largest polluters of mercury today. Other polluters have also weighed in on the issue and lobbied for lax controls, no regulation, and no warning to the people. The fisheries industry has fought long and hard to sell their product despite the mercury content. The FDA has had to sort through flawed research provided by industry funded scientists, and bad data out of a poisoning that occurred in Iraq that set our current standards for mercury in fish. This has resulted in a murky advisory, and little or no testing of the mercury content of the suspect large predatory fish that are in our markets.

10. With developing countries like China and India building more coal-fired power plants every week, why should we be concerned about cutting mercury pollution here in the U.S.? Aren't we still going to be inundated with airborne mercury from other countries?

Mercury from coal burning power plants is both a global and local issue. Although a portion of the emissions reaches high in the atmosphere and gets distributed far and wide, it also contaminates locally. Two studies have identified an increase in autism rates in children growing up in areas that have higher mercury emissions. Wildlife and the environment in general have been shown to be adversely affected by mercury emissions that occur locally.

11. Are there other concerns with long term methylmercury exposure?

There are other areas that are of concern for individuals who chronically consume methylmercury enough to raise blood levels over 5.0 mcg/l. No safe level has ever been found for chronic exposure. The main health concerns include a possible increase in coronary artery disease and heart attack or stroke, neuropsychiatric damage, autoimmune antibodies, immune dysfunction, infertility, and type 2 diabetes. At this time, it appears there is a genetic susceptibility at play, which is why there is such a wide variability in tolerance between individuals.

12. What can I do to help curb mercury pollution?

Because many of the biggest, most dangerous mercury polluters are huge industrial sources like cement kilns and power plants, trying to stop these polluters individually has been a challenge. By supporting groups working for strong regulations and laws to protect our health and environment like Earthjustice, you can definitely play a part. Sign up for email action alerts, stay informed about what's happening in your neighborhood, town and state, let your elected officials, health department, and local medical society know that mercury pollution is dangerous and that we need to take action immediately to protect ourselves and our children against this harmful threat.