Mercury contamination of drywall

James Vallette | March 18, 2010

This blog post, originally shared in the Pharos Signal, includes information about parts of Pharos that are no longer available. Please use it for historical reference and for the other useful information it contains.

Last year, the U.S. Environmental Protection Agency ran tests on six drywall products, two from China, and four from the United States. These tests raise an alarm about an element that has been little discussed in the Chinese drywall scare: mercury.

The EPA tests identified mercury in four of these products. The two China-made wallboards contained mercury at 0.19 and 0.562 parts per million (ppm). Two U.S. wallboards also had mercury -- one at a minute 0.0668 ppm, and one at a level much higher than any other (2.08 ppm).

The precautionary principle requires us to identify wallboard manufacturing practices that generate mercury. Using U.S. Toxics Release Inventory (TRI) data, we have identified specific drywall products manufactured at plants that release mercury. Additional literature, including last year's EPA test, convinced us that mercury not only is released in certain factories, but also is present in some wallboard products.

The precautionary principle led us to add mercury as a frequent trace (0.1%) ingredient of wallboard that is manufactured at plants that report mercury releases. For wallboard manufactured in countries that do not require TRI-like emissions reporting (which is most of the world), we list mercury as a trace ingredient of products that use synthetic gypsum generated by coal-fired power plants.

Mercury in synthetic gypsum

The wallboard with the highest concentration of mercury found in last year's EPA study was made with synthetic gypsum. The vast majority of synthetic gypsum is generated from Flue Gas Desulfurization units of coal-fired power plants. Certainly, the use of FGD has decreased direct releases into the environment from modernized coal-fired power plants. The reuse of this captured material that would otherwise be stacked or landfilled is also a positive. The Pharos renewable/recycled content evaluation rewards products that contain post-industrial waste, including FGD-derived gypsum. But, specifiers should consider this positive evaluation in the context of the common presence of mercury in the synthetic gypsum production life cycle.

A review of 2008 Toxics Release Inventory data from U.S. wallboard manufacturers reveals a direct correlation between substantial mercury releases to the environment and the use of synthetic gypsum.

Gypsum wallboard plants reported a total of 472.8 pounds of mercury releases in 2008. The top five mercury releases all came from wallboard plants that use FGD-derived synthetic gypsum. Lafarge's Palatka, Fla. and Silver Grove, Ky. plant led all releases with 143 and 124 pounds, respectively. Pharos subscribers may now examine our evaluations of products from these Lafarge facilities, which we released this week.

Other leading drywall manufacturing sources of mercury releases include two US Gypsum plants in Aliquippa, Pa. (58 pounds) and Gypsum, Ohio (25 lbs.), and, CertainTeed's Proctor, W.V., (32 pounds). These five plants accounted for 82% of reported wallboard plant mercury releases in 2008.

These synthetic gypsum wallboard plants represent a secondary release point for coal-fired power plants' mercury emissions. The FGD units capture mercury from coal. Wallboard production using synthetic gypsum then redistributes the mercury into the wider environment at the production site, and through the board itself. As a December 2009 US EPA study notes, "both fly ash and FGD residues have been identified as coal combustion residues with the potential to have increased mercury and/or other pollutant concentrations from the implementation of new air pollution technology."

Mercury in natural (mined) gypsum

It also appears that natural (mined) gypsum also can contain mercury, albeit at lower levels. A U.S. Dept. of Energy-funded study, conducted by U.S. Gypsum (which uses more synthetic gypsum than any other U.S. manufacturer), concludes, "the highest mercury concentration found in the natural gypsum was 0.03 µg/g compared to the lowest mercury concentration of synthetic gypsum of 0.10 µg/g."

Some -- but not most -- plants that do not use FGD-derived gypsum in wallboard production also reported mercury compound releases in 2008 (11 plants, 37.8 pounds total). (Toxics Release Inventory data) For product manufactured at these specific plants, we have added mercury as a trace contaminant in the product's material contents.

Mercury-free wallboard

One wallboard manufacturer, Serious Materials, has obtained UL-Environment verification of its claim that its EcoRock is "mercury-free." Serious Materials, unlike the vast majority of wallboard manufacturers, does not use gypsum in EcoRock. So, for this manufacturer at least, the issue of mercury contamination is an important market distinction.

We welcome similar verifications of any wallboard profiled by Pharos, particularly those that have reported mercury releases in the past three years. If a manufacturer provides us with third-party documentation that drywall made in these facilities is mercury-free, we will remove mercury compounds from the product material contents list.

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Pharos researcher Jim Vallette will be speaking at the Maine Indoor Air Quality 2010 Conference at the Augusta Civic Center, March 24. Click here for more info.