Mercury in Fish

What is mercury?

Mercury is an element that occurs naturally. It is released into the environment by both natural processes and human activity. This means there are small amounts of mercury in lakes, rivers and oceans.

How do fish get contaminated by mercury?

It happens through the food chain. In the bottom sediments of rivers, lakes, and oceans, mercury undergoes methylation, a process carried out by bacteria in certain conditions. Small fish eat small snails, crawfish and insects that have eaten even smaller things containing methylmercury. Then larger predator fish, like bass, eat the smaller fish. Since bass are at the top of the freshwater food chain, they can build up methylmercury. Methylmercury then gets into the food chain and results in mercury exposure to persons who eat fish.

Why does Louisiana have a problem with mercury in fish?

The problem of mercury in fish is not unique to Louisiana, it is a global problem that many other states and countries are working to address. Mercury in fish is not new, either. In fact, scientists believe the levels of mercury found in our fish today are probably similar to those of the past 50 years. What is new is that we know more about mercury's harmful effects now than we did 50 years ago, and we can better measure mercury in fish.

The Louisiana Departments of Environmental Quality and Wildlife and Fisheries periodically sample fish from lakes and rivers across the state. The Louisiana Department of Health then evaluates the data that is provided and determines the need for an advisory.

How can this affect my health?

Mercury usually causes no symptoms at low levels. However, if high levels of mercury build up in the human body, they can affect the brain and nerves. In addition, effects that can occur at high levels include learning problems and birth defects in children. Among people of all ages, high mercury levels can cause tingling or numbness in the mouth, hands and feet, and vision and hearing troubles. The primary source of environmental exposure to mercury in the general population is through consumption of contaminated fish. That’s why prevention of mercury build-up in our bodies is so important. Those who should be most careful when eating fish are:

  • Children under 7-years old,
  • Pregnant women,
  • Women who are planning pregnancies,
  • Women who are breast-feeding their babies, and
  • People who eat a lot of fish over a long time from mercury advisory areas.

Unborn babies and children under 7-years old are at risk because their nervous systems are still forming, and any harm to those systems might be permanent. Pregnant women and women who are nursing their babies should be very careful about eating fish which contain high levels of mercury. Pregnant women can pass mercury from the fish they eat to their unborn babies, and nursing mothers can pass the mercury to their infants through their breast milk. Adults who have health effects caused by mercury simply can stop eating mercury-contaminated fish, and in most cases their health problems will go away as their bodies slowly get rid of the mercury.

What do I do if I think I have been exposed?

It is not likely that there is an immediate need to be concerned about the health effects of mercury. Fish advisories are issued as a precaution. However, you should consult your doctor if you are concerned.

Should I stop eating fish?

Doctors recommend fish as an important, low fat source of protein, but where mercury is present in those fish, it is important that certain people know the rules when eating fish caught from waters under mercury health advisories. The fact that mercury is found in fish from some Louisiana waters does not mean you have to quit eating fish. But if you eat large amounts of fish which contain mercury over a long period of time, you might experience health problems. There are no special cleaning or cooking methods that will take mercury out of fish. But there are some things you can do to reduce your health risks:

  • Ask where the fish was caught, and call 1-888-293-7020 or check the Louisiana Department of Health Website to see if there is a fish advisory for that body of water;
  • Read the fish advisory and follow its directions about which fish to avoid or which fish you should eat less often;
  • Eat younger and smaller fish, since they usually contain less mercury; and
  • Get your fish from more than one body of water or source.

Where can I get more information about mercury in fish?

Call 1-888-293-7020, toll-free, for more facts about mercury in fish and to request a current list of mercury advisories issued for Louisiana waters.

For information on the US Environmental Protection Agency's (EPA) and Food and Drug Administration’s (FDA)federal advisory for women of childbearing age, pregnant women, nursing mothers and young children, go to