Before the exhaust from Mirant’s Alexandria power plant goes up the smokestack, it is cleaned with a powder called trona to neutralize the acid it contains. Yet there have been very few studies of trona’s impact on public health.

Mirant began using trona regularly at the Alexandria plant in January 2006, after the possibility was raised that the plant could exceed national air quality standards.

“After researching technologies that reduce sulfur dioxide (acid) emissions, trona was selected as the best technology for the plant,” Mirant spokeswoman Felicia Browder told The Examiner in an e-mail. “The trona system has proven to be very effective, with a 60 percent reduction in sulfur dioxide emissions.”

U.S. Rep. James Moran, a Democrat who represents Alexandria and Arlington, requested a study of trona’s health implications as part of the 2008 federal interior appropriations bill.

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If it passes, the Environmental Protection Agency will study trona’s health effects. Trona is a safe mineral similar to baking soda, according to Solvay Chemicals, the company providing Mirant’s trona.

But in high concentrations, the substance can irritate people’s lungs, eyes and skin, according to a report drafted by the Virginia Department of Environmental Quality (DEQ) this summer. DEQ’s report cites two University of Utah studies published in the early 1980s on the health of trona miners.

Twenty-three percent of respondents in those studies described a chronic cough, though this was more prevalent in smokers than non-smokers. Sixty percent reported eye and nose irritations. The incidence of skin irritation was two to 15 times higher than what it had been before the study participants began working at the trona mine. This was due to irritation, not allergy, the report concluded.

Solvay Chemicals cites a 2000 industry study on its Web site that showed no signs of irritation to Wyoming miners’ eyes, noses or lungs during an eight-hour shift.

Miners are exposed to trona at much higher levels than people living around the Alexandria plant, said David Fowler, a senior toxicologist with the federal Agency for Toxic Substances and Disease Registry.

“The main thing is that nobody knows about [the health effects of trona when used to neutralize acid in emissions],” Fowler said.

As a result, Fowler said, the health effects on people breathing the air around a plant using trona aren’t definitively known.

mhegstad@dcexaminer.com