What is mercury?

Mercury is a chemical that is found in nature.

How does mercury get into the environment?

It is released into the environment by nature and human activity. This means there are small amounts of mercury in lakes, rivers and oceans.

How does mercury get into the bodies of fish?

  1. Under certain conditions, bacteria come in contact with mercury after it enters rivers, lakes, and oceans. A chemical reaction happens and the mercury is changed into methylmercury.
  2. Small fish eat snails, crawfish and insects that have eaten smaller things that contain methylmercury.
  3. Larger fish eat smaller fish (predator fish).
  4. Predator fish store methylmercury in their bodies.

This entire process is a type of bioamplification (or biomagnification) – a term that describes an ecologic process that results in increasing concentrations of a toxin in the bodies of organisms with each succeeding trophic level. The trophic level of an organism is the position it occupies in a food chain or pyramid.

Why is mercury in fish a problem in Louisiana?

  • Louisianans eat a lot of the fish they catch from bayous and waterways. Fish is rich in protein and essential oils, and a healthy part of a balanced diet. But, there are healthy limits to eating fish since they may contain small amounts of mercury. These recommended limits vary by each person, such as children, pregnant women and healthy adults.
  • It can take quite a while, from months to years, for the human body to process and clear mercury completely.
  • Mercury in fish is not new. It is also not a problem that is unique to Louisiana. Many other states and countries are working to address the health risks of mercury.
  • Scientists have shown the levels of mercury found in our fish today are similar to those of the past 50 years.
  • We know more about mercury's harmful effects than we did 50 years ago and can better measure mercury in fish.

How is Louisiana addressing the problem with mercury in fish?

  • The Louisiana Departments of Environmental Quality (LDEQ) and Wildlife and Fisheries (LDWF) periodically sample fish from lakes and rivers across the state.
  • After the fish samples are collected, the Louisiana Department of Health reviews the data and decides if guidance for limiting or avoiding certain fish from certain water bodies or types of water bodies need (fish consumption advisories) to be issued.

How can this affect my health?

At low levels

  • Mercury usually causes no symptoms at low levels.

At high levels

  • Mercury build up in the human body and can affect the brain and nerves.
  • Some of the health problems that have been found in children include birth defects and learning problems.
  • Tingling or numbness in the mouth, hands and feet, and vision and hearing problems have been found in people of all ages who have come in contact with high levels of mercury (mercury poisoning).

How do people come in contact with mercury?

Most people come in contact with mercury from eating fish that contain mercury. Learning how to prevent mercury for building up in our bodies can reduce our risk.

Groups that have a greater risk from eating fish that contain mercury include:

  • children under 7 years of age;
  • pregnant women;
  • women who are planning to get pregnant;
  • women who are breast-feeding, and
  • people who eat a lot of fish for a long time from areas with fish advisories.

Why do certain groups have a greater risk of coming contact with mercury?

  • Unborn Babies and Young Children:
      Unborn babies and children under 7 years of age are at risk because their nervous systems are still forming and any harm to those systems might last forever.
  • Pregnant and Nursing Women:
      Pregnant women and women that are nursing their babies should be very careful about eating fish that contain high levels of mercury. Pregnant women can pass mercury from the fish they eat to their unborn babies. Nursing mothers can pass the mercury to their infants through their breast milk.
  • Adults and limiting mercury contact:
    Adults who have compromised health or health problems from eating fish that contain mercury should stop eating high mercury fish. 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 come in contact with mercury?

  • It is not likely that there is an immediate need to be concerned mercury is causing health problems. Guidance for limiting or avoiding certain fish from certain water bodies or types of water bodies is issued as a precaution.
  • You should talk to your doctor if you are concerned. Tests are available to measure mercury levels in the body. The blood can be tested to find out if people have come in contact with methylmercury. Your doctor can take the sample and send it to a lab.

Should I stop eating fish?

  • Doctors suggest that we eat fish because it is a low fat source of protein. If mercury is present in these fish, it is important that people know about the guidance for eating fish caught from waters under fish advisories.
  • Find out which fish are lower in mercury.
  • Remember if you eat large amounts of fish that contain mercury over a long period of time, you may experience health problems.
  • Note: no special cleaning or cooking methods will remove mercury from fish

What can I do to reduce my risk?

  • Ask where the fish was caught.
  • Call the Louisiana Department of Health at 1-888-293-7020 or visit their website to find out if there is a fish advisory for the waterbody where you fish.
  • Read the fish advisory and follow the directions about which fish to avoid or which fish you should eat less often.
  • Eat younger and smaller fish because they usually contain less mercury.
  • Get your fish from more than one body of water or source.

Where can I get more information about mercury in fish?

  • Fish Advisories and Information on Mercury: Call the Louisiana Department of Health at 1-888-293-7020 for information on mercury in fish and to request a current list of mercury advisories issued for Louisiana.
  • Information on Groups at Risk: 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 the EPA's website.




Environmental Sampling - Mercury Levels in Fish

Currently, there are 49 mercury advisories in Louisiana.

Because people have come in contact with mercury from eating fish in Louisiana, popular fishing areas and other water bodies in the state have been sampled by the Louisiana Department of Environmental Quality (LDEQ) to determine the extent of risks due to mercury. Fish advisories are issued when harmful chemicals are found at levels that may impact the public's health. To explore mercury in fish data, click here

Bayou Bonfouca - No Swimming

Image provided by the LDEQ

Tracking Mercury Levels in Fish in Louisiana

The Health Data Explorer, is the Department’s online data exploration tool. It contains measured mercury concentrations in fish tissue for over 500 locations statewide and are available for a variety of species. Some locations have periodic data going back to 1994. Data are presented by species and sampling location. An arithmetic mean of contaminant concentrations in wet weight is displayed for each species. For questions regarding mercury data please contact LDEQ's Water Planning and Assessment Division.