The defective drywall issue was first publicly reported almost a year ago with stories of sulfuric odors and metal corrosion in homes in Southwest Florida built with Chinese drywall. Now, 1,897 residents in 30 states, the District of Columbia and Puerto Rico have submitted complaints about defective drywall to the U.S. Consumer Product Safety Commission.
Because the issue is something experts have never come up against before, answers on what to do next have been slow in coming.
Federal studies have yet to make a definitive link between the drywall and the corrosion or health problems, although studies have found that Chinese drywall emits elevated levels of volatile sulfur gases and contains higher levels of strontium than domestic wallboard.
Studies have not shown these chemicals to be at toxic levels. However, homeowners have complained of problems such as headaches, nosebleeds, respiratory infections, eye and throat irritation and stuffiness.
A study released last week by the U.S. Consumer Product Safety Commission and other agencies suggests that homeowners may be experiencing 'neurogenic inflammation' from non-toxic levels of chemicals like sulfur compounds, although it did not say whether those chemicals could be from the drywall or other things in the home.
Certain Chinese-made wallboard installed in thousands of Florida homes has been found to emit sulfuric odors and gases responsible for corroding electrical wiring, air conditioning components, bathroom fixtures such as toilet handles and even jewelry.
Strontium sulfide, a material that can emit corrosive gases in moist air, was found at trace levels in testing of Chinese-made drywall, the Florida Department of Health said.
Gas emitted from defective drywall corrodes copper wiring, turning it black, some Florida homeowners say.
The Florida Department of Health said complaints generally involve homes built between 2004 and 2007, around the time a building boom and post-hurricane reconstruction caused a U.S. drywall shortage and spurred builders to use imports.
The latest testing, commissioned by the Florida Health Department and conducted by private laboratory Unified Engineering Inc. of Illinois, found that three samples of what the department believes is Chinese-manufactured drywall had "several physical and chemical differences" from a fourth, U.S.-manufactured drywall sample, Krause said.
The samples suspected to be from China contained trace levels of strontium sulfide, and the U.S.-made product did not, according to Unified's report.
Strontium sulfide can react in moist air to form hydrogen sulfide -- a gas that smells like rotten eggs, according to the Web site of the National Oceanic and Atmospheric Administration.
Hydrogen sulfide is corrosive, according to a Web page of the Occupational Safety and Health Administration. Exposure to low levels of the gas "may cause irritation to the eyes, nose or throat ... [and] may also cause difficulty breathing for some asthmatics," according to the federal Agency for Toxic Substances and Disease Registry.
The Chinese-made drywall emitted a sulfurous odor when exposed to extreme heat in testing, while the U.S.-made product did not, according to Unified's report. However, the report doesn't conclude that the strontium sulfide contributed to the odor. "Because initial tests only detected small quantities of this substance, further tests are necessary to determine if it is the cause of odors and corrosive gases," Krause said.
Unified also found that the outer paper and core of two samples -- a piece of Chinese-made drywall and a piece of the U.S.-made drywall -- emitted trace levels of hydrogen sulfide and two other volatile, sulfur-containing gases when put into a chamber and exposed to 95 percent humidity.
One of the emitted gases was carbon disulfide, Unified's report said. Breathing it at low levels for long periods "may result in headaches, tiredness, trouble sleeping and slight changes in the nerves," according to the Web site of ATSDR, which is part of the U.S. Department of Health and Human Services.
The emission tests were useful in determining what the drywall may produce, but conclusions cannot be drawn about health risks, Krause said. That's in part because the concentrations of emissions captured in laboratory testing are not useful to determine what concentrations would be found in the much larger volume of air in homes, he added.
"We shouldn't interpret it for anything at this point," Krause said. "These are not exposure measurements."
The Unified test results showed that heat and humidity play a key role in getting the drywall to emit the odors.
"This may explain why the problem has developed in South Florida first, where hot and humid conditions prevail," Krause said.
A Unified test also showed that sulfide gases in a Florida home that contained Chinese-made drywall were the main reason that an air conditioner's copper tubing corroded, Krause said. The report did not say whether the gases came from the drywall.
Earlier testing by ENVIRON International, a private consulting firm hired by a Florida-based homebuilder, found that certain drywall manufactured in China was emitting sulfur gases capable of ruining copper coils in air-conditioning systems.
However, it said it found air samples in the homes showed no indication that health hazards existed.
The Consumer Product Safety Commission is "already sending additional experts from headquarters to Florida to further our investigation," commission spokesman Joe Martyak said.
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