What do fish, fluorescent light bulbs and coal-fired power plants have in common? The answer is mercury – the toxic heavy metal that’s been linked to neurological and developmental disorders in children, and cardiovascular disease, neurological and other problems in adults.

Consumer Reports has long analyzed mercury levels in fish to provide consumers with the best advice for avoiding  species of fish with  high levels of the heavy metal. A new study of mercury exposure in New York City  confirms the importance of making wise choices.

The New York City Health Department recently analyzed blood samples for mercury and other heavy metals and found significantly higher levels in people who ate more fish. Levels were also notably higher among wealthy New Yorkers, presumably those who eat more expensive fish such as that found in sushi.

A non-profit environmental group known as the Turtle Island Restoration Network, also analyzed samples of tuna purchased from New York City sushi restaurants, finding nearly half of the 13 samples analyzed contained levels of mercury that exceeded the levels that the FDA considers safe for some women and young children. Some samples even exceeded 1.0 ppm, the level that FDA considers unsafe for human consumption.

Fish is an important part of a healthy diet, but studies suggest that frequently eating species with high mercury levels may interfere with the health benefits that the omega fatty acids found in fish would otherwise provide. Avoiding high mercury fish is especially important for pregnant and breastfeeding women, those who may become pregnant and young children.

When we look at how mercury gets into fish in the first place, we find that protecting the safety of our fish supply depends on manufacturers and consumers making wise decisions about other products as well, not just which fish to eat. Mercury doesn’t just float into the fish supply by itself. It gets there in large measure from manufacturing processes and from use and disposal practices that have pumped mercury into the air and water for centuries.

Mercury has been used in a wide range of products including dental fillings, electrical switches, thermometers and batteries. Mining metals and the burning of fossil fuels, primarily coal, are among the greatest causes of mercury releases in the environment. Disposal of mercury-bearing consumer products also releases a substantial amount of mercury. While there’s little that can be done to clear the oceans and fish stocks of mercury that’s already out there, cutting back on energy consumption, finding alternative energy sources, and getting mercury out of consumer products are all important ways to help keep the problem from getting much worse.

Ironically, careful use of a modern product that contains trace amounts of mercury, the compact fluorescent bulb, is one strategy for achieving net reductions in environmental mercury releases. As our recent story on compact fluorescent light bulbs (CFLs) explains, the trace amount of mercury present in these long-lasting energy-saving bulbs is an unfortunate but worthwhile trade-off to cut energy use that contributes to the much larger amounts of environmental mercury that come from coal-fired power plants.

Because health officials have not been able to identify a level of mercury exposure that’s safe, it’s especially important to keep as much mercury out of the environment as possible and to lower your own exposure to mercury. That means limiting or eliminating your intake of high mercury fish species, reducing energy consumption and avoiding or carefully managing mercury-bearing products as they are used and discarded. For CFLs, that means careful clean-up if they break and recycling them when they reach the end of their useful life. Sylvania, for example, sells a mail-back recycling package.