CPSC Releases Study of Chinese Drywall

To date, CPSC has received more than 2000 reports from 32 states, the District of Columbia and Puerto Rico, from consumers and homeowners concerned about alleged problem drywall from China in their homes. The majority of consumer complaints on allegedly defective drywall have come from Florida and Louisiana.

The CPSC last week released a study of Hydrogen Sulfide Gas in connection with its Chinese drywall investigation.  Specifically, CPSC released results from a major indoor air study of 51 homes, and initial reports from two studies of alleged corrosion in homes with Chinese drywall. The 51 home study was actually contracted by CPSC and done by Environmental Health & Engineering (EH&E). The  two preliminary reports on corrosion safety issues are from the Sandia National Laboratories’ (SNL) Materials and Engineering Center concerning the long-term electrical safety hazards of conductor metal components, and the National Institute of Standards and Technology (NIST), studying the corrosion effects on fire safety components taken from complaint homes.

EH&E compared 41 “complaint” homes in five states selected from CPSC’s consumer
incident report database, with 10 non-complaint homes built around the same time in the
same areas as the complaint homes. Homes were sampled between July and September
2009. The EH&E findings were that hydrogen sulfide gas appears to be 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 appear to contribute to the
reported problems.  The reports do not explain how the hydrogen sulfide gas is being created in homes built with Chinese drywall. (Earlier studies found varying amounts of elemental sulfur in the Chinese drywall.)

In terms of method, EH&E exposed copper and silver test strips, known as coupons, in homes for a period of about two weeks. The coupons showed significantly higher rates of corrosion in complaint homes than in the control homes. The dominant species of corrosion on the coupons were 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 EH&E study also found that by using hand-held x-ray fluorescence and Fourier Transform Infrared instruments, they were able to detect markers that could identify Chinese-made dry wall at a sheet-by-sheet level.

The study did not link the corrosion with any long term safety effects, which are still under investigation. The levels reported, however, are well below the amount associated with long term health effects in the literature.

Like the EH&E study, initial reports from SNL and NIST show copper and silver sulfide corrosion on samples of metal taken from homes with problem drywall.

In terms of next steps, CPSC continues to search for homes exhibiting the alleged corrosion and health effects under study. Second, the federal Interagency Task Force has established an Identification and Remediation Protocol Team of scientists and engineers. This Team will try to use the results of the EH&E study and other information to design a screening protocol to identify homes with this problem.  Because professional air sample testing, and destructive testing of drywall both are costly, the Protocol Team is trying to develop quick, cost-efficient evaluation methods to identify homes with these problems. The 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.

CPSC believes it has secured the cooperation of the Chinese Government to help identify the sources and causes of this problem. The agency believes that no new Chinese drywall has entered the United States in 2009. CPSC is also working with an ASTM committee that has just initiated discussions on the formulation of a proposed new standard on inspection of drywall for air quality issues.

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