Mercury

Did You Know?

Because mercury accumulates in the muscle tissue (filet) of the fish, neither preparation (trimming skin or fat) nor cooking method reduce mercury exposure. The best way to reduce mercury exposure from fish is to eat mostly small fish, which naturally contain less mercury.

Larger fish that have lived longer (swordfish, tuna, shark, king mackerel and tilefish) have the highest levels of mercury because they have had more time to accumulate it. In general, smaller fish like sardines and scallops contain less mercury.

Breastfeeding mothers should minimize exposure to mercury in their diets, at home, and at work.

Mercury is a naturally-occurring element in the environment and is also released into the environment through human activities such as burning coal and oil. Mercury collects in streams, lakes, and oceans, where fish and other animals are exposed. Small amounts of mercury are also used in making common household items like fluorescent bulbs and some thermometers.  People who work in recycling plants, who manufacture items with mercury, and who handle dental amalgam might have some mercury exposure on the job.

How might mercury affect breastfeeding mothers and babies?

Mercury can pass from a mother to her baby through the placenta during pregnancy and, in smaller amounts, through breast milk after birth. Exposure to mercury can affect the infant’s brain and nervous system development during pregnancy and after birth.

How much and what types of fish are recommended for breastfeeding women to consume?

Although mercury naturally occurs throughout the environment, the mother’s diet is the primary source of mercury exposure for most breastfed infants before they are introduced to complementary foods. Most fish contain some level of mercury.  When a mother eats fish, the mercury in the fish can be passed into her breast milk. However, the benefits of breastfeeding may be greater than the possible adverse effects of exposure to mercury through breast milk.

Although fish remains an excellent source of protein and essential vitamins and minerals for breastfeeding women, some care must be taken in how much and what kind to eat. The U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) have issued fish consumption guidanceexternal icon for pregnant and breastfeeding women and young children:

  • Eat a variety of fish.
  • If you eat fish caught by family or friends, check for fish advisoriesexternal icon. If there is no advisory, eat only one serving and no other fish that week.
  • Try to avoid eating the “Choices to Avoid” fish or feeding them to children. It is best to eat a variety of fish from the “Best Choices” and “Good Choices” categories on this chartexternal icon.

For adults:

  • 1 serving = 4 ounces of fish, measured before cooking. Eat 2 to 3 servings (between 8 and 12 ounces) of fish a week from the “Best Choices” list OR 1 serving (4 ounces) from the “Good Choices” list on this chartexternal icon.

For children:

  • A serving is 1 ounce at age 2 and increases with age to 4 ounces by age 11. Serve fish to children 1 to 2 times per week from a variety of fish. Portion sizes should be smaller than adult portions and based on your child’s age and calorie needs.
  • Currently there are no specific recommendations about the amount or frequency of fish consumption for infants (breastfed or non-breastfed) younger than age 2.

How can breastfeeding mothers and their families protect themselves from mercury at home?

Handling an intact lightbulb or thermometer that contains mercury does not cause mercury exposure.  If a mercury-containing lightbulb or thermometer breaks, however, it can spill mercury onto surfaces and release mercury vapors into the air. If this happens, families should be advised to follow the EPA instructions on safe clean-up of a broken mercury-containing lightbulbexternal icon or broken mercury thermometerexternal icon.

How can breastfeeding mothers reduce their exposure to mercury at work?

Women who are concerned about mercury exposure at work should be advised to talk to their supervisor or safety officer to discuss ways to avoid or reduce exposure to mercury.  Information on how to reduce mercury exposure in different jobs is available from the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA),external icon and on this fact sheet pdf icon[PDF-77KB]external icon.