Last spring I wrote that drywall imported from China was leaking sulfur into homes across America. Now there’s more reason not to love this wall system. The Environmental Protection Agency reports that it’s found mercury and formaldehyde lurking in some drywall products.
Drywall with the highest mercury content was made from synthetic gypsum. Photo By future15pic/Courtesy Flickr.
Last year EPA tests on four drywall products from the United States and two from China found mercury at varying levels in two of the U.S.- made products and in both of the Chinese-made ones. While three of the products contained mercury at low levels (0.0668 to 0.562 parts per million), one of the American-made products contained 2.08 ppm, an alarming amount of mercury.
The drywall with the highest mercury content was made from synthetic gypsum, which is created from Flue Gas Desulfurization (FGD) units at coal-burning plants. When coal is burned, it emits sulfur dioxide. To reduce SO2 emissions, FGD systems spray the gas with limestone, which reacts with the sulfur dioxide to create a liquid sludge that, when dried out, is then turned into drywall. The FGD units also capture mercury from the burning coal, which is transferred into the final product.
Last year during the initial drywall scare, many health advocates expressed concern about the combined harmful effects of sulfur and formaldehyde emissions. At the time, the EPA said that drywall was not a potential source of formaldehyde emissions, but EPA testing in 2009 did find formaldehyde in the core boards of American-made drywall products. In 2003, the State of California also tested gypsum drywall boards for formaldehyde emissions and found that the products emitted more formaldehyde than was safe by the state’s standards.
When selecting drywall for new home construction, keep a few questions in mind. What is the drywall made of? If a product is made of synthetic gypsum, it will likely outgas mercury into your home. Where is the drywall made? Drywall manufacturing is very energy intensive, giving this product a high carbon footprint. Drywall made overseas will have a higher carbon footprint, and drywall made in China could be leak sulfur into your home.
The Pharos Project offers in-depth information on green building materials. The site is designed for green building professionals, but you can register for a week-long free trial. The California Waste Management Board also offers a list of recycled-content drywall.