Most chlorine plants in the U.S. have turned from old manufacturing processes requiring mercury to newer ones that don"t. In fact, 100 factories across the globe have switched to mercury-free production, since it also requires less energy (and lowers costs). But four chlorine or chlor-alkali plants—in Georgia, Ohio, Tennessee and West Virginia—still use the outdated process, which involves producing chlorine by pumping saltwater through a vat of mercury, creating an electrolytic chemical reaction, and releasing mercury emissions that later settle in the water and contaminate fish. Chemicals produced by these plants are in a vast range of consumer products, from plastic and PVC (polyvinyl chloride or vinyl) to food additives like MSG and sodium benzoate as well as in bleach, toothpaste and pharmaceuticals.
The plants don't come close to the mercury emissions of coal-fired power plants, but they still emitted more than 700 pounds of mercury in 2007, according to information from the nonprofit Oceana, one of several environmental groups pushing for a bill that would force these plants to change their practices.
Oceana's campaign has involved broadcasting the benefits of switching from mercury: which will expand plants" capacity, and make them more efficient to the extent that they should realize payback from conversion in five years or less. The group has also lobbied to get grocery stores to post the Food and Drug Administration's warnings related to mercury in seafood. And they've backed a bill called the Mercury Pollution Reduction Act introduced in the House in 2009 that would permanently phase out the use of mercury in the manufacture of chlorine—but that bill has never made it out of committee.