The Consumer Product Safety Commission's (CPSC) much-anticipated study of Chinese drywall has linked metal corrosion to the defective wallboard. However, the agency said that more investigation is needed to determine what long term hazards the defective Chinese drywall may pose.
According to a statement from the CPSC, results from a major indoor air study of 51 homes, along with initial reports from two studies of corrosion in homes with Chinese drywall, confirmed that the presence of hydrogen sulfide is the essential component that causes copper and silver sulfide corrosion found in the complaint homes. Other factors, including air exchange rates, formaldehyde and other air contaminants contribute to the reported problems, the agency said.
The CPSC's study was conducted between July and September 2009. The tests, conducted by Environmental Health & Engineering, an internationally known environmental testing firm based in Massachusetts, compared indoor air quality on 41 homes that had been the subject of Chinese drywall complaints, and 10 homes that had not. Copper and silver test strips, known as coupons, were exposed in all homes for a period of about two weeks.
According to the CPSC, the coupons showed significantly higher rates of corrosion in complaint homes than in the control homes. The dominant species of corrosion on the coupons was copper sulfide and silver sulfide, as determined by additional laboratory tests. Visual inspection and evaluation of ground wire corrosion also revealed statistically significant greater ground wire corrosion in complaint homes compared to non-complaint homes.
The study also found elevated formaldehyde readings in both the control and complaint homes. Both formaldehyde and hydrogen sulfide are known irritants at sufficiently high levels. While the concentrations measured in this study were below those levels, the CPSC said investigators believe that the additive or synergistic effects of these and other compounds in the subject homes could cause irritant effects seen in the homes.
The CPSC said it is still studying the long term safety effects of the Chinese drywall. The Sandia National Laboratories' Materials and Engineering Center is studying the long-term electrical safety hazards of conductor metal components. The National Institute of Standards and Technology is studying the corrosion effects on fire safety components taken from complaint homes. According to the CPSC, these ongoing investigations will help identify any associations between Chinese drywall and long term safety issues.
The CPSC said it will be using the results from this study and other information to design a cost-effective screening protocol to identify homes with problem drywall. Its Identification and Remediation Protocol Team will also look at remediation protocols, to see what cost-efficiency improvements to current remediation practices, if any, may be available, and what guidance should be issued on doing the work safely, the agency said.
So far, the CPSC has received 2,091 reports from residents in 32 states, the District of Columbia, and Puerto Rico concerning Chinese drywall. The agency said it is continuing to search for homes exhibiting the corrosion and health effects under study. In addition to a direct call to consumers, the CPSC is contacting governors of all states, all territories and the District of Columbia, to ensure that all homes with these problems have been reported to CPSC.