CPSC Staff Preliminary Evaluation of Drywall Chamber Test Results, March 2010

1 Due to the interrelated nature of these investigations, these technical reports are being released in draft until the final results from further studies are available for interpretation. These studies are staff level documents and have not yet been reviewed or approved by the agencies participating in this investigatory effort. Executive Summary U.S. Consumer Product Safety Commission (CPSC) staff contracted with Lawrence Berkeley National Laboratory (LBNL) for measurement of chemical emissions from 30 samples of drywall products obtained as part of an investigation of imported (Chinese) drywall. In this report, non-Chinese drywall is referred to as North American or NA. The objectives of this preliminary evaluation are to: (1) Evaluate chemical emissions from Chinese drywall and from drywall from other sources (2) Identify the possible differences in chemical emissions between the two sources of drywall products (3) Evaluate the possible chemical exposures in homes that contain either of these two sources of drywall. The LBNL data contained measures for the following reactive sulfur compounds-hydrogen sulfide, sulfur dioxide, carbon disulfide, methyl mercaptan, dimethyl sulfide, and carbonyl sulfide. CPSC staff used the LBNL reported emission rates in a mathematical model to estimate the concentrations of the chemicals in the indoor air of a home that might result from the presence of drywall. A simple one-zone model was used to estimate concentrations of reactive sulfur gases. The model accounted for factors, such as air exchange rate and room volume, which impact the concentrations of chemicals in the indoor air. It was assumed that the ceilings and walls of all rooms in the home were covered with drywall. In addition, the model includes reactive decay rates to account for the chemical reaction between the reactive gases and surfaces in the room, such as furniture and carpeting. There are a number of uncertainties that limit the ability of the model to accurately estimate the levels of sulfur gases in actual homes. The tested wallboard samples were from a warehouse, where the stacking may have limited emissions of the sulfur compounds during storage and increased the tested chamber emissions relative to drywall that had been installed in homes. The tested drywall samples were not painted or otherwise coated, which likely increased drywall emissions relative to drywall installed in a home. Homes may have drywall from multiple manufacturers and sources. There is a general lack of data on reactive decay rates for the sulfur gases. The decay …