A few years ago, when his state's legislators were debating a ban on mercury thermometers, Richard Judd would have gladly pointed them to a much bigger threat. Down the road from his home in Orrington, Maine, sat 260,000 pounds of the potent toxin in corroding vats at an aging chlorine plant.
"You could look out over what was really a lake of mercury almost the size of a basketball court," he recalls of a tour he once took of the plant. "I just could not have imagined that much mercury in one spot. It's incredible when you know that one teaspoonful can contaminate a small lake."
For those trying to highlight the link between mercury pollution and the industry that makes the basic ingredient for everything from household bleach to paper, such disregard seems typical. While public attention focuses mostly on coal-fired power plants spewing mercury into the air, nine old-line chlorine plants in the United States are also leaking an equally large amount, environmentalists say.
Or at least, they may be. On top of the 5 to 7.7 tons officially "emitted" into the environment, according to various estimates, far more tons of mercury mysteriously disappear every year during chlorine manufacturing. Older plants use mercury to create chlorine. "A lot of people just don't know there's this other source of mercury out there," says Dawn Winalski, pollution-projects manager for Oceana, a Washington environmental group that released a scathing report about the chlorine industry's mercury problems last week.
The 13 million to 14 million tons of chlorine produced in the US annually is used to purify water, bleach paper, and make myriad products: from car dashboards to bulletproof vests.
Although the industry has significantly reduced the amount of unaccounted-for mercury, no one knows for sure where it's located. In 2000, for instance, these chlorine plants reported 79 tons of mercury consumed, according to federal and industry data cited in the report. Fourteen of those tons were emitted or released into the environment; the rest - 65 tons - was officially classified as "unaccounted for" by the US Environmental Protection Agency (EPA).
That's an amount that shocks environmentalists because, by contrast, the nation's 497 mercury-emitting power plants sent 49 tons of the toxin into the air that year, Oceana reports.
"Sixty-five tons of mercury is a lot," says Jon Devine, a lawyer for the Natural Resources Defense Council (NRDC). "If a significant amount of this stuff is going out into the atmosphere, then these plants could rival power plants in terms of their contribution to mercury emissions in the US."
Chlorine industry officials argue that most of the mercury probably stays on the factory site trapped inside equipment and factory pipes.
"The chlorine industry can account for 99 percent of our total mercury inventory - but we realize that's not good enough," Tracy Cullen, a spokeswoman for the Chlorine Institute in Arlington, Va., writes in an e-mail. "We're fully committed to 100 percent accountability. And we're now working with EPA on new, more advanced methods for monitoring fugitive air emissions."
The best information so far indicates that unaccounted-for mercury is not being leaked into the air, the EPA says. Also, the industry's mercury consumption has fallen from an annual average of about 160 tons in the early 1990s to 30 tons in 2002, an 81 percent drop.
Even so, what happened to the missing mercury is a mystery. "The fate of all the mercury consumed at mercury cell chlor-alkalai plants remains somewhat of an enigma," the EPA declared in 2003 in the Federal Register.
"We agreed to conduct a detailed study to help us account for the mercury," says Cynthia Bergman, an EPA spokeswoman in an e-mail. "The unaccounted-for mercury from mercury cell chlor-alkalai plants is a very important issue to the agency."
Environmentalists contend that while the mercury may start out in the vats of old-line chlor-alkalai plants, it may well evaporate into the atmosphere, wafting out windows - or leak into the soil and water around these plants.
"The EPA darn well better find the lost mercury from chlorine plants because people's health depends on it," says Linda Greer, a scientist with the NRDC. "But the larger issue is that there is no reason for these plants to continue consuming mercury to produce chlorine."
Indeed, most of the 43 chlor-alkalai manufacturing plants in the US today use advanced mercury-free manufacturing processes that are relatively clean. But nine US factories - and 53 older ones in Europe - still use older "mercury-cell" technology that requires huge quantities of mercury to do the same job, Oceana reports.
The mercury-cell process involves pumping salt brine through mercury vats, or "cells." Each cell can be more than 50 feet long and 5 feet wide and hold in the neighborhood of 8,000 pounds of mercury. An electric current flowing into the cell creates a reaction that produces chlorine and caustic soda, also called lye.
Even though most factories have shifted to nonmercury technologies, the Chlorine Institute does not support phasing out mercury's use. "There is no good reason to eliminate more US manufacturing jobs by closing plants that are operating safely and performing above and beyond all federal and local standards," writes Ms. Cullen.
It's not clear whether regulators will force a change. Despite growing pressure to clamp down on mercury emissions, "Clear Skies" legislation reintroduced last week in Congress is focused primarily on power plants.
Environmentalists hope, however, that modifications to another new federal rule, currently being reviewed by the EPA, will target lost mercury from chlor-alkalai plants. The original rule was delayed after the NRDC and Sierra Club sued the EPA, arguing it would not adequately deal with unaccounted-for mercury.
Meanwhile, Europe is moving ahead to phase out mercury in its chlor-alkalai plants by 2007. In 2000, the mercury-cell chlorine plants in the first 15 member states of the European Union reported using 104 tons - with 96 tons of that unaccounted for, Oceana reports.
With phaseout, however, arises a major problem over what to do with hundreds of tons of mercury inside these older plants.
In Maine, after the mercury-cell chlorine plant near Mr. Judd closed, the mercury was sold to a broker who planned to sell more than 100 tons of it abroad. An outcry by environmental groups brought a shipload of 20 tons, already bound for India, back to the US. Today, the bulk of the mercury sits in Wisconsin storage tanks, Maine environmentalists say.
"I lived next to that plant for 10 years without any idea there was that much mercury there," Judd says. "People would tell us it was a chlorine plant. But that's what you put in your pool, right, to clean up water? We all use chlorine in our washing machines, swimming pools, and everything else. It took us awhile to wake up."
Discovered in 1774, this greenish-yellow gas (after the Greek chloros, "greenish yellow") is so reactive that it appears on Earth only combined with other elements, especially sodium, to create salt. Among chlorine's many uses:
• Water purification. It's employed the world over to help purify drinking water and to clean swimming pools.
• Plastic: Polyvinylchloride or PVC pipe is the preferred conduit for sewage and water supply because it doesn't rust.
• Bleach: Besides the household variety, chlorine compounds are used to bleach pulp for paper.
• Poison gas: Fatal at high concentrations, chlorine became a weapon in World War I.
Sources: CRC Handbook of Chemistry and Physics; American Chemical Society; Environmental Literacy Council