Although mercury has been a well-known toxin for decades, it is only recently that studies have revealed the damaging effect mercury exposure can have on the brains and nervous systems of developing children. Knowing how to decrease your exposure to mercury during pregnancy is essential to preventing lasting neurological damage in your child.
What is mercury?
Mercury, often called quicksilver, is a naturally occurring metal. While most people think of mercury as the shiny, silver-white substance used in traditional thermometers, this form of mercury—known as elemental, or metallic mercury—is only one of three forms the metal can take. The other two are mercury salts and organic mercury (mercury combined with other elements, such as carbon).
Although all three types of mercury are natural components, a number of human activities have contributed to an increase in the amount of organic mercury, specifically methylmercury, present in the atmosphere and in water sources.
What does mercury exposure do to humans?
Mercury has been recognized as toxic to humans longer than the cliché “mad as a hatter” has been in use; in fact, the term was used to describe the symptoms of mercury poisoning exhibited by felt hatmakers from the 17th and 18th century who regularly used mercury-based compounds.
Today, mercury is recognized as a dangerous neurotoxin: both methylmercury and elemental mercury are poisonous to the nervous system, particularly to the developing brains of unborn children, infants and young children.
What happens when fetuses, infants or young children are exposed to mercury?
While children and adults may suffer from the symptoms of mercury poisoning—weakness, uncoordinated movements and sudden problems with talking, hearing and walking—it is fetuses exposed in the womb who show the most dramatic effects of mercury exposure.
Studies have consistently shown that unborn children exposed to mercury (specifically methylmercury) are born with deficits in memory, attention, language and cognitive thinking, as well as both fine motor and visual spatial skills.
The studies have also indicated that the nervous systems of fetuses are much more vulnerable to damage from mercury: levels of exposure that did not result in symptoms of mercury poisoning in pregnant mothers often resulted in infants born with severe neurological disabilities.
What are the most common sources of mercury exposure?
The consumption of methylmercury in fish and shellfish is the most common source of mercury exposure.
When methylmercury from fossil fuel emissions or improperly disposed mercury-containing products find their way into rivers, lakes and streams, it is absorbed into the tissues of many fish and shellfish. Humans who eat the contaminated seafood then absorb the methylmercury directly into their own tissues.
And, for pregnant women, this means that the mercury is transferred directly to the developing tissues of the unborn child.
How can pregnant women avoid mercury exposure?
According to the National Academy of Science, women who consume large amounts of fish and shellfish during pregnancy run the highest risk of having children suffering from mercury-related neurological damage.
While eating seafood moderately during pregnancy is considered safe and healthy, pregnant women should avoid large fish that are known to contain higher concentrations of methylmercury. These fish include shark, swordfish, tilefish and King mackerel.
Pregnant women can safely eat 12 oz. per week of cooked fish other than these larger fishes, including shellfish, canned fish, ocean or farm-raised fish. The most commonly eaten fish that are consistently low in mercury include shrimp, salmon, catfish, pollock and canned light tuna.