You are what you eat, but if fish is on your fork several times a month, you could be poisoning yourself.

Many forms of fish are great for people, there's no doubt about it. But because of several factors, mainly the pollution from coal-generated power facilities that produce energy for many homes, mercury levels are rising inside of our bodies.

In many fish, mercury built up under the scales and shells can cause adverse health problems if eaten by people. Children and women of childbearing age are at an increased risk, according to the government and environmental advocacy groups.

Most fish is lean and full of healthy omega-3 fats, but some species are also laden with mercury, a harmful toxin that can interfere with the central nervous system and brain.

The Natural Resources Defense Council, sourcing the Environmental Protection Agency and Food and Drug Administration, listed fish safe to eat and fish to avoid.

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Images: Fish To Eat, Avoid

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Mercury has been used for making thermometers and thermostats and in some chemical and industrial facilities. The real problem arises once the pollution moves into the air and makes its way into oceans and waterways, building up in the fish people eat, according to NRDC.

Once mercury enters a waterway, naturally occurring bacteria absorb it and convert it to a form called methyl mercury," according to information published by NRDC. This transition is particularly significant for humans, who absorb methyl mercury easily and are especially vulnerable to its effects.

Mercury then works its way up the food chain as large fish consume contaminated smaller fish. Instead of dissolving or breaking down, mercury accumulates at ever-increasing levels.

Scientists have said that predatory fish such as large tuna, swordfish, shark and mackerel can have mercury concentrations in their bodies that are 10,000 times higher than those of their surrounding habitat.

According to the EPA, if a pregnant mother eats fish contaminated with mercury, it can harm the fetus' growing brain and nervous system, which can affect cognitive thinking, memory, attention, language and other motor and visual spatial skills.

It also affects growing children because they absorb more nutrients as their brains and nervous systems develop.

By far, people ingest the highest amounts of mercury through tuna because it is one of the most popular fish to eat, according to environmental groups.

It is also important for fisherman to check local advisories because some fish are so highly contaminated that they should not even be eaten at all.

Local Fish Advisories: Pennsylvania | New Jersey | Delaware

Greening Your Way To Mercury Reduction

Eating fish brings mercury into people's bodies, but if you've feasted on lobster and tuna your whole life, don't panic. There are ways to cut mercury contamination inside your body and in the environment.

Restrict Portions Or Don't Eat Fish At All:

Obviously, people who cut fish out of their diets will consume much less mercury than those that eat it.

If cutting fish out of the diet isn't an option, people can drop mercury levels inside their bodies by choosing to eat fish with lower levels of the toxin and by eating less of it. Most doctors say it takes several months for levels to drop. Blood tests can detect mercury levels.

Need another reason? Think about how much energy goes into getting crab legs harvested thousands of miles away onto your plate. Ships have to span long distances in dangerous conditions to catch the crabs, return to land, ship them to other parts of the world and make sure they are refrigerated through the entire process.

Many species are also harvested using environmentally destructive methods and are perilously low in numbers, which could affect how some people chose their meals, too.

Heat Your Home With Clean Energy

Remember, one big source of mercury pollution comes from power plants.

Many are not in a financial or geologically feasible position to install solar panels, geothermal heating systems or windmills in their back yards.

Still, there are options. Many power companies, including Peco, offer programs where customers can purchase wind power instead of fossil-fuel-generated heat. You won't have the windmill in your yard, but the company will purchase the same amount of wind power for the power grid.

Stay Informed, Become An Activist

Stay on top of environmental laws and loopholes associated with cutting industrial and power plant emissions.

According to NRDC's Web site:

By law, the Environmental Protection Agency is obligated to require power plants to cut roughly 90 percent of their emissions of mercury and other toxic pollution by 2008. Instead, in March 2005 the agency let polluters off the hook, requiring much smaller reductions and giving electric companies more than two decades to accomplish them. What's more, the agency essentially allowed polluting companies to do nothing for the next 12 years.

The nonprofit organization also said people should ask their grocery stores, fish markets and restaurants to label fish and post warnings about the dangers associated with the fish they sell.