July 5, 2001- It's in the water we drink, the air we breathe, the food we eat, and the fillings in our teeth. Not to mention some thermometers and until recently, vaccines.
It is mercury and it can be toxic to the developing brain and nervous system of fetuses and children. That's why in a new report published in the July issue of the journal Pediatrics, pediatricians are encouraging parents to avoid mercury, whenever possible, by properly discarding mercury thermometers and limiting the type of fish that they eat and feed their children.
The number one way to reduce the amount of mercury that ultimately makes its way into the environment is to safely get mercury thermometers out of the home, says report author Michael W. Shannon, MD, MPH, a member of American Academy of Pediatrics' committee on environmental health and a pediatrician and toxicologist at Children's Hospital in Boston.
Each mercury thermometer contains approximately one gram of mercury. One gram of mercury per year deposited in a 20-acre lake is enough to raise the levels of mercury in fish high enough to trigger consumption advisories. Nationwide, mercury fever thermometers contribute 17 tons of mercury to the solid waste stream annually.
"The reason fish have become so contaminated is that there is so much mercury in the environment and that's due to owning and improperly discarding mercury thermometers and sometime, batteries," Shannon tells WebMD.
Charlotte Brody, RN, the coordinator of Health Care Without Harm, an international campaign designed to reform the environmental practices of the healthcare industry, agrees that mercury thermometers need to be taken out of homes. "Even people who are careful with them, break them," she tells WebMD.
Many replacements for mercury thermometers are available, from the simplest digital thermometer that costs a few dollars to very sophisticated ear thermometers that can cost almost $100, Brody says.
Mercury is a hazardous material so it must be disposed of carefully, such as during a community's hazardous material recycling day. Health Care Without Harm works with hospitals all over the country to run mercury fever thermometer exchange programs.
The problem with mercury is that when it reaches the water, it easily transforms into extremely toxic methylmercury, which then accumulates in the food chain - eventually showing up in the fish we eat.
That's why, in March 2001, the FDA recommended that pregnant women and women of childbearing age should not eat shark, mackerel, swordfish, or tilefish because of their too-high mercury content. Children and nursing moms should limit the amount of shark and swordfish that they eat to no more than one serving per week. Children and pregnant women should eat less than 12 ounces of all other fish, including tuna, per week (about two cans).
"We have no evidence that women have been harmed, but we are looking to be as protective as possible having learned more and more that mercury has toxicity," Shannon says.
Shrimp, fish sticks, flounder and haddock all have low levels of mercury, so "people are well-advised to vary the fish that they eat," Brody says.
Fortunately, others are concerned about the dangers of mercury in the environment. A type of mercury used as a preservative in vaccines is currently being phased out. And although many dentists still use silver fillings containing mercury, scientists in the U.S. have concluded that the risks of the fillings in teeth are low and that the available substitutes are not superior.