Mercury rising

Mercury from coal burning and other sources works its way through the food chain and accumulates particularly in fish, casting a shadow on an otherwise healthful source of protein. Since the start of the Industrial Revolution, mercury levels in the environment have increased three to six times depending on the region. While much of an area's mercury comes from distant sources, a Florida study released this fall showed that states can also reduce their exposure substantially by limiting local emissions.

With its goal of reducing smokestack mercury pollution in Massachusetts by 95 percent by 2012, the regulation proposed by the state Department of Environmental Protection is laudably ambitious. One devil in the details is its clause allowing plant owners who have trouble meeting the goal to opt for an off-site "alternative reduction plan."

Instead of cleaning emissions to the required level, a utility could arrange for the collection and proper disposal of other sources of mercury. These could include school laboratories or the mercury in many electric switches.

But the state's proposed regulation specifically says that off-site mercury reductions "otherwise required by law or regulation" will not qualify. This raises the obvious question -- why aren't there already state standards for mercury disposal at these other sources?

Even if there are unregulated sources of mercury that a utility could help clean up, it is unlikely that such sources would become as dangerously dispersed as smokestack mercury. The DEP acknowledges this by proposing that a utility get just a half-pound credit for each pound of mercury secured off-site. But the public might still be better off by insisting that utilities clean up the most harmful source of the toxin: their stacks.

The US Environmental Protection Agency proposes to let polluters buy cleanup credits from other polluters who exceed requirements. But the Florida study shows that letting a plant continue to emit mercury creates a hot spot for nearby residents. The EPA plan would reverse a Clinton administration standard that held that mercury, like other toxins such as asbestos or lead, should be reduced through "maximum achievable technology."

New technology has cleaned mercury in city incinerators and has also worked with coal-fired plants. Tough state and national standards can ensure that this technology protects the public from coal plant mercury.