The Healthy Geezer: Does Mercury Cause Cancer?

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Question: Can you get cancer from eating fish that contains mercury?

High levels of mercury exposure can harm the brain, heart, kidneys, lungs, and immune system of people of all ages. There isn't enough human data available for all forms of mercury to conclude that it causes cancer.

However, the U.S. Environmental Protection Agency (EPA) has determined that methylmercury is a possible human carcinogen.

Mercury, a liquid metal also known as quicksilver, combines with carbon to make organic mercury compounds; methylmercury is the most common one. Methylmercury is made primarily by microscopic organisms in water and soil.

Methylmercury builds up in the tissues of fish. Larger and older fish tend to have the highest levels of mercury. Research shows that most people's fish consumption does not cause a health concern.

Almost all fishand shellfishcontain traces of mercury. However, some fish have higher levels of mercury that can harm the developing nervous system of a fetus or young child. The risks from mercury in seafood depends on the amount and type that is consumed.

The EPA and the U.S. Food and Drug Administration (FDA) give the following advice to those at highest risk such as pregnant women:

* Do not eat shark, swordfish, king mackerel or tilefish. These have high levels of mercury.

* Eat shrimp, canned light tuna, salmon, pollock, and catfish. These are low in mercury.

Albacore, or white meat tuna, has more mercury than canned light tuna.

* Contact your local health department to check local advisories about the safety of fish caught in nearby waters.

(An important added note: fish sticks and fast-food fish sandwiches are usually made from seafood low in mercury. )

Mercury is a naturally occurring element that is found in air, water and soil. In addition, mercury enters the air from mining ore, burning coal and waste, and from manufacturing plants. It enters the water or soil from natural deposits, disposal of wastes, and volcanic activity.

Exposure to mercury occurs from breathing contaminated air, ingesting contaminated water and food, and having dental and medical treatments.

Pure mercury has been used to make thermometers, switches, pressure gauges, fluorescent bulbs, button batteries, thermostats, dental fillings and medicines.

In recent years, there has been a growing focus on the need to decrease the use of mercury in products and to prevent the mercury in existing products from entering the waste stream. Several states have passed legislation to reduce mercury in waste.

So how about those fillings in your mouth?

Dental amalgam is the silver-colored material used to restore teeth that have cavities. Dental amalgam is made of liquid mercury and a powder containing silver, tin, copper, zinc and other metals. Mercury concentration in dental amalgam is generally about 50 percent by weight.

Is dental amalgam safe? Here's the official answer from the American Dental Association:

Dental amalgam is considered a safe, affordable and durable material that has been used to restore the teeth of more than 100 million Americans. It contains a mixture of metals such as silver, copper and tin, in addition to mercury, which binds these components into a hard, stable and safe substance. Dental amalgam has been studied and reviewed extensively, and has established a record of safety and effectiveness.

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Fred Cicetti is a contributing writer for Live Science who specializes in health. He has been writing professionally since 1963. Before he began freelancing, he was a reporter, rewriteman and columnist for three daily newspapers in New Jersey: The Newark News, Newark Star-Ledger and Morristown Record. He has written two published novels:" Saltwater Taffy—A Summer at the Jersey Shore," and "Local Angles—Big News in Small Towns."