A "strong association" exists between homes where Chinese drywall was installed and where occupants reported smells and corroded metals, the U.S. Consumer Product Safety Commission (CPSC) reported last week. The finding clears the way for a federal task force to figure out how many houses have this problem and what to do about it.

The report released today (see executive summary) lends government-funded scientific support to the notion that Chinese drywall used in homes in recent years is behind complaints of rotten-egg smells, corroded metal connections, tarnished jewelry, and equipment breakdowns in homes across the United States. CPSC says it has received 2,000 reports from 32 states, the District of Columbia, and Puerto Rico regarding problem drywall in their homes, and liability lawsuits have been filed.

How many homes could be affected remains uncertain, says the CPSC, which recently reached out to the governors of every state and U.S. territory for data. The agency does know that roughly 7 million sheets of Chinese drywall were imported between 2000 and 2009. What it doesn't know is how many of those sheets went into homes and what percentage has problems.

Today's conclusions are based on several studies of 51 homes in Florida, Louisiana, Virginia, Alabama, and Mississippi. An independent testing firm, Environmental Health & Engineering (EH&E), was hired to look at all 51, including 41 where there had been complaints. After two weeks of exposure in the homes, copper and silver tests showed "significantly higher rates of corrosion in complaint homes than in the control homes," CPSC said. "... Visual inspection and evaluation of ground wire corrosion also revealed statistically significant greater ground wire corrosion in complaint homes compared to non-complaint homes."

EH&E personnel also used X-ray and infrared devices to detect markers that could identify Chinese-made drywall at a sheet-by-sheet level.

"The EH&E findings are that hydrogen sulfide gas is the essential component that causes copper and silver sulfide corrosion found in the complaint homes," CPSC said. "Other factors, including air exchange rates, formaldehyde and other air contaminants, contribute to the reported problems."

In addition, Sandia National Laboratories' (SNL) Materials Science and Engineering Center evaluated metal corrosion believed to have occurred in homes exposed to the problem drywall. "A preliminary visual inspection by CPSC Electrical Engineering staff of all of the harvested electrical components revealed substantial corrosion of copper wiring, but there were no indications of significant overheating of conductors or conductive parts due to the corrosion events," CPSC reported.

Meanwhile, the National Institute of Standards and Technology examined copper natural-gas supply tubing and two air-conditioner heat-exchanger coils. "A thin black corrosion product was found on all of the copper samples examined," CPSC said. "Chemical and structural analysis of this layer indicated that this corrosion product was copper sulfide. ... Corrosion products were also observed on other types of metals in the air conditioning coils in the areas where condensation would frequently make the metals wet."

With all this new evidence, CPSC concluded, "We now can show a strong association between homes with the problem drywall and the levels of hydrogen sulfide in those homes and corrosion of metals in those homes.

"By identifying this association, the Interagency Drywall Task Force can now move forward to develop protocols that will identify homes with this corrosive environment and can determine the effectiveness of remediation methods," CPSC continued. "The task force continues to work with Congressional and White House officials to determine the best approaches to design and fund these identification and remediation efforts to help the families dealing with this issue."

Studies to determine long-term safety effects are under way.

The Interagency Task Force already has established an Identification and Remediation Protocol team of scientists and engineers. "This team will use the results of the EH&E study and other information to design a cost-effective screening protocol to identify homes with this problem," CPSC said. "Professional air sample testing and destructive testing of drywall can carry high costs. The Protocol Team will 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."

For more on the government's activities and to download reports, go to the CPSC's special website on drywall.

Craig Webb is the editor of ProSales magazine.