17th July 2007

What is mercury?

Mercury is a naturally-occurring element which is found in soil and rocks and also exists in lakes, streams and oceans. In addition to natural sources, mercury is released into the environment by human activities such as pulp and paper processing, mining operations, and burning garbage and fossil fuels.

Mercury enters streams, rivers, lakes and oceans primarily through rain and surface water runoff. Bacteria can then convert it to an organic form called methylmercury -- the form that is dangerous to people. Although mercury levels are almost always low in water bodies, methylmercury biomagnifies up the food chain. When small fish with low mercury levels get eaten by bigger fish, the amount of mercury biomagnifies. For this reason, long-lived fish and top-level predators like swordfish and shark often have the highest mercury levels. According to EPA, mercury concentrations in fish can be 1 to 10 million times the mercury concentration in the water.

It is well known that high amounts of mercury can damage the nervous system of people and animals. In trace amounts, however, the effects are not clearly known. Long-term studies are being conducted to determine the effects of low levels of mercury, especially on young children.

Mercury in fish

We have always been led to believe that eating fish is good for our health. However, how many of us know that in America alone, one-in-six children born every year may have been exposed to mercury levels so high that they are potentially at risk for learning disabilities and motor skill impairment as well as short-term memory loss. One government analysis shows that 630,000 children each year are exposed to potentially unsafe mercury levels in the womb.

There is no doubt that fish and shellfish are an important part of a healthy diet. Fish and shellfish contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids. A well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children's proper growth and development. So, women and young children in particular should include fish or shellfish in their diets due to the many nutritional benefits.

However, nearly all fish and shellfish contain traces of mercury. For most adults, the risk from mercury by eating fish and shellfish is not a health concern, unless the levels are excessively high. Yet, some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child's developing nervous system. The risks from mercury in fish and shellfish depend on the amount eaten as well as the levels of mercury in the fish and shellfish. The Food and Drug Administration (FDA) and the