September 4th, 2009

By Barbara Kessler
Green Right Now

Here’s a little cautionary tale about how bigger is not always better — and about the inter-connectedness of our energy and food systems, specifically how coal-fired power plants affect your diet.

Say you were camping with friends and caught a really BIG fish. This monster would give you bragging rights for a year. Now say you caught a smaller fish, suitable for pan frying but not Kodak-worthy.

What do you do? If you’re Daniel Boone, you toss the little guy back. It’s a no brainer. But if you’re a post-industrial age sportsperson, you must consider this: That big fish fillet could be disproportionately loaded with mercury; keeping the little fishy could be safer.

According to recent sampling studies by our federal government, ALL of our freshwater fish are contaminated, to some extent, with mercury. And the way mercury works its way through the food chain is that it builds momentum, so that those higher on the food chain are more contaminated — a process called “biomagnification”. And some of those big fish contain a mercury that’s become more toxic, too, after the mercury has been acted on by bacteria found in wetlands and swamps and converted to the more dangerous methylmercury.

The science is complicated, but you don’t need a biology degree to get the gist of things, that our fish are coming to us in less than pristine condition.

Fishy Findings

The US Geological Survey study tested fish from 291 streams across the country and found that all tested positive for traces of mercury, demonstrating how widespread mercury pollution has become. But scientists also reported that only about one-quarter had mercury levels exceeding the EPA’s safe guidelines for people eating “average amounts of fish.”

Still. ALL of the fish tested in the US showed some levels of mercury contamination. (The levels of mercury ranged from .008 to 1.95 parts per million – or micrograms per gram of wet tissue.)

This left us to wonder: Are we supposed to be alarmed? What can we now safely eat? Must we forfeit fresh fish along with all those ocean varieties that are endangered?

The answers: Yes and no. Some fish. No, but sometimes yes – can be confusing.

The government’s FAQs on this topic only left us feeling more uneasy about our future meals and also more than a little helpless about the air pollution at the root of it all. They explain that mercury is a “potent neurotoxin” in fish, wildlife and humans, yet they note that fish are “important part of a healthy diet.” We did know that: Fish are high in protein and healthy oils.

So officials are advising us to continue to eat fish, but with caution. The public should:

• Make “informed decisions” based on EPA and FDA guidelines.
• Check our state advisoriesUSDA guidelines to find out which freshwater fish are most affected and where.
• Kids and women of child-bearing age need to take special care because mercury can be harmful to developing bodies, and especially minds. They should eat no more than two meals a week that contain fish that are “lower in mercury,” according to the

“We don’t want to scare people away from eating fish, because they’re a healthy source of protein, but they should pay attention to state fish consumption advisories and also the EPA and FDA guidance for consumption of commercial fish,” says Mark E. Brigham, a hydrologist with the U.S. Geological Survey, a leader on the study and an expert in mercury in biological systems.

Isn’t that a lot to ask of consumers who are already busy reading food labels, trying to shop “the outside aisles” of the grocery store, searching for information on how livestock was fed and trying to find the hormone-free milk?

Pause…. “We want informed consumers,” says Brigham.

In case you think freshwater fish present a minor culinary concern, you should know that the federal government estimates about 34 million people fish for sport and food. No doubt many more fancy catfish at the neighborhood fish fry and patronize lakeside restaurants looking for walleye and perch.

To be fair, though, Brigham isn’t on the food side of this issue, but the fact-finding science side. He understands that his team’s discovery -  that every last fish tested had some traces of mercury – is not a comfort to the fish-eating public. But it was not surprising.

Mercury, he points out, “is a pervasive contaminant in the environment.” It is the second leading cause of “impaired” water systems – the first is pathogenic contamination, such as bacterial infections – and has been tracked for many years. Forty-eight of the 50 states issue advisories on mercury in fish.

In addition, “there’s always been a natural component to the mercury cycle. It does get emitted from volcanoes and is “degassed from the earth” and rained back down into waterways.
That’s the good news within the bad news.

A human-made problem

The really bad news, though, is that historical sampling of lake beds shows that mercury contamination from natural sources was slight compared with the rapid accumulation from post-industrial activities.

Knowingly and inadvertently, humans have spewed significant mercury into the earth’s biological systems, waterways and atmosphere as we’ve developed cement plants, mercury and gold mines, metal smelting and coal-burning power plants.

Some of that pollution has been cleaned up as we’ve realized that dumping industrial waste directly into streams and lakes, no matter how giant (think: Lake Erie) is not a good idea.

But the main contributor to the global “mercury cycle’” is coal power plants of which there are 491 in the US and hundreds more around the world, such as in China, which is building coal plants faster than anyone.

Coal-fired power plants account for 40 percent of all mercury emissions in the US, according to the EPA.

The top 50 most-polluting US coal-burning power plants emitted 20 tons of toxic mercury into the air in 2007, according to a study by the nonprofit Environmental Integrity Project.

All US coal plants collectively emit some 48 tons of mercury annually, according to a Government Accountability Office (GAO) report, preliminarily released in July.

That mercury gets emitted as oxidized, elemental or particulate-bonded forms. The oxidized or particulate-bonded mercury falls to the earth relatively quickly, contaminating the local region and watersheds — but it can also be captured more easily. The elemental mercury, though, can ride in the atmosphere, joining mercury emissions from around the world, Brigham said, which explains why his study group found mercury in fish in areas distant from known sources of mercury.

Furthermore, certain natural conditions, present in wetland environments and forests, enhance a process that converts mercury into methylmercury, which is easily taken up by aquatic life. This leads to the seeming paradox of some fish in relatively undeveloped watersheds and pristine areas having some of the highest elevated levels of mercury (in the rural South and wild wetlands of the Pacific Northwest and Midwest); and complicates the matter of knowing what is safe to eat.

The best way to help save our freshwater fish, and their ocean cousins, from further injury, Brigham, among others, have concluded, would be to reduce those mercury emissions at their source.

(Though remember, some fish is safe to eat all the time, and other fish is safe to eat some of the time, like once a week, if it’s the right type…Check your advisories.)

Dialing back mercury emissions

The EPA first tried to reduce mercury emissions from coal plants with a 2005 regulation called the Clean Air Mercury Rule. But it was thrown out by the courts, which advised the agency to employ the Clean Air Act to set mercury emission guidelines.

The EPA is in the midst of trying to make this change, but a new rule must meet certain tests. The Clean Air Act requires, for instance, that standards for other pollutants in the same category, known as “Hazardous Air Pollutants” (lead, toxic gases and dioxin) be set simultaneously.

Once a rule is written and approved, coal-fired plants will be required to use the latest technological advances to cleanse mercury from their admissions. It can be done: Some coal plants in the US have already added scrubbing technology, required by more stringent state guidelines, proving that removing the mercury is possible.

Furthermore, according to the July GAO report technology to remove mercury is effective and affordable.

Coal plants with the technology already in place are removing 80 to 90 percent of the mercury in air emissions.

Coal’s CO2 emissions, blamed for rising carbon in the atmosphere, will not be affected by this new rule

Resources:

• GAO Testimony to the US Senate committees and subcommittees concerned with food and environmental health.
• EPA list of State Fish Advisories
• Effects of Mercury on People on the EPA

(Photos of: Fish in a Pan by ZKruger/dreamstime.com; brook trout by Eric Engbretson, US FWS; boy fishing by Ronald Laubenstein, US FWS.)

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