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Unless you're like The Addams Family's Uncle Fester, who delighted in occasionally having a mercury thermometer as a snack,
any mercury exposure you may suffer probably comes from eating certain types of fish. Unfortunately, that favorite "sandwich fish" of ours—"solid white" tuna—is one of the most contaminated little fishies.
What other fish have a mercury problem, how did things get this way, and what should we do about it? The first question we'll tackle is how planet earth turned into planet mercury.
Although people can experience problems if exposed directly to elemental mercury, the normal way for them to get a dose of mercury is from a piece of fish. But mercury is not a natural toxin in fish, so how did it get there?
The chain of events goes something like this:
- Mercury gets into the air as a byproduct of industrial activities such as chlorine production, power generation from coal, garbage incineration, automobile recycling, and some mining and manufacturing processes.
- From there, the airborne mercury is deposited on land and water, where microorganisms convert it into a more biologically active form, methylmercury.
The methylmercury then works its way up the food chain. Because organisms tend to store mercury, not excrete it, concentrations of mercury get higher and higher as larger, longer-living creatures gobble up smaller ones. By the time you get to a top predator fish like a swordfish, albacore tuna, or shark, the concentrations are quite high.- When humans eat these fish and some others, they get the mercury that's in the fish flesh.
According to the Physicians for Social Responsibility, research has shown that:
- short-term exposure to high concentrations of mercury vapor has harmful effects on the nervous system, digestive system, respiratory system, and kidneys;
- long-term exposure to mercury can permanently damage the brain and kidneys at any age;
- long-term animal studies have also found that exposure to organic mercury (such as methylmercury) at high levels can cause nervous system damage; damage to the kidneys, stomach, and large intestine; changes in blood pressure and heart rate; adverse effects on male reproductive organs, sperm, and developing fetuses; and an increase in the number of spontaneous abortions and stillbirths.
Because mercury is particularly troublesome for developing nervous systems, fetuses, infants, and young children are most at risk. The National Academy of Sciences states that mercury in pregnant women disrupts the development of brain cells in their babies. A January 2003 report by Centers for Disease Control concluded that one in six women of childbearing age have mercury in their blood above the level that would pose a risk to a developing fetus. Clearly, pregnant women and parents of young children should take extra precautions.
On the surface, this one's easy: anyone who's dragging their feet on reducing mercury air pollution. We should realize, though, that most of us have enjoyed the benefits of cheap-but-dirty coal-generated electricity for decades, as well as the fruits of the other industrial processes the cause mercury pollution. Still, many manufacturing sources have been greatly cleaned up, and the focus is now squarely on coal-fired power plants.
It's a shame that our leaders have let the mercury problem fester for so long. It would have been worth a few extra bucks every month on our power bills to keep the fish supply clean. But it's better that we take action late instead of never.
Unfortunately, some of the talked-about improvement plans for coal-fired power plants
don't move nearly as far or as fast as necessary to correct this problem. Proponents of the Clear Skies Initiative have touted a 70% reduction of mercury by 2018. Seventy percent sounds pretty good, but a previous EPA analysis showed that a 90% reduction could be achieved in a period of just a few years. Additionally, Clear Skies allows a cap-and-trade setup to be applied to mercury, which is not appropriate because it will saddle some states and communities with toxic mercury hot spots. (Read more about this in our article about Cap and Trade Systems.)
Some politicians are claiming that the technology does not exist to achieve a near-term 90% reduction in mercury emissions from power plants, but they're wrong. We should hold their feet to the fire to achieve the 90% level sooner rather than later. So, when you hear a politician brag about "an unprecedented 70% reduction in mercury emissions," know that he's giving you second best.
Voting for politicians that will stop mercury pollution at its source is important. (See Environmental Voting Guide.) So is making sure you reduce mercury exposure for you and your family. Here are several useful tools that will help you determine which fish are safe to eat and in what quantities.
- PSR Guide: The Physicians for Social Responsibility (PSR) has a nice wallet-sized card that rates fish for mercury contamination. However, be sure to pay attention to the little "over-fished" symbol next to some species so you don't solve your mercury problem only to contribute to the decline of a disappearing fish species.
[See http://www.mercuryaction.org/fish/learn_more.html]
- Tuna Tabulator/Tuna Calculator: The PSR Guide follows the US FDA's rather lax guidelines for consumption of tuna. The Natural Resources Defense Council has put together a table for tuna consumption based on the US EPA's more cautious mercury guidelines. It lets you figure out the safe amount of tuna for you or your child based on body weight and tuna type (solid white or chunk light). Similarly, the Environmental Working Group has a calculator-style tool that helps you do the same thing.
[Tabulator: http://www.nrdc.org/health/effects/mercury/tuna.asp
Calculator: http://www.ewg.org/tunacalculator]
Caught fish: Remember that some geographical areas are exposed to more mercury than others, so fish that you, your family, or your friends catch from local bodies of water could be more contaminated than the national average. More than 40 states have released local-fish advisories tied to mercury, and recent US EPA data show that more than three-quarters of fish sampled from the nation's lakes had mercury levels that may be unhealthy for women of childbearing age and children younger than 3. (And the rest of us can take our chances, I guess.) The FDA advises that you check with your state government for advisories about the safety of fish in your local lakes, rivers, and coastal areas. If no advice is available, they recommend you eat no more than 6 ounces per week of any fish you catch from local waters and that you not consume any other fish during that week.
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