The reports show that Beijing Building Materials shipped nearly 38 million pounds of drywall to the U.S. in 2006. Sun Yong, the company's vice president, said it didn't matter whether the wallboard was made with mined gypsum or phosphogypsum.
"From China's customs side, there is no special inspection of exported drywall," he said.
Health concerns,
inconclusive tests
Phosphogypsum contains radium, prolonged exposure to which can lead to a higher risk of lung cancer, and that is why the EPA banned phosphogypsum for use in construction in 1989.
Dr. Paul Papanek, a board member of the Western Occupational and Environmental Medical Assn., said the health effects of contact with phosphogypsum are not immediate. Medical studies about how often the substance causes cancer are inconclusive, he said.
Chinese building-material managers say they have seen an increasing number of drywall makers mixing phosphogypsum in production. They said the corrosion of coils and metals seen in American houses was consistent with drywall made with that ingredient.
For similar reasons, a top manager at Tai'an Single Mechanical & Electrical Technology Co., a supplier of gypsum-processing equipment in Shandong province, also suspects phosphogypsum as a root cause.
The manager, who spoke on the condition of anonymity, estimates that 80% of Chinese drywall makers use phosphogypsum because it is cheap and there are no government restrictions.
Gypsum drywall in China is used largely for businesses, and industry associations say there have been few complaints in China like those from American homeowners.
So far, tests in the U.S. of Chinese-made drywall used in American homes have not turned up evidence of phosphogypsum. In Florida, four samples taken from troubled houses showed no indication of radium, said Lori Streit, a scientist at Unified Engineering Inc., which conducted the analysis.
Streit said the rotten-egg-like odor and corrosion are associated with volatile sulfuric acids, and some industry officials say that could mean the drywall was made with gypsum from mines in eastern China's Tai Mountain area, where ores have unusually high levels of sulfur compounds.
Knauf, a German company that has a joint-venture operation in China and has been a primary target of lawsuits over bad drywall, has acknowledged using gypsum from that area.
Which watchdog
is responsible?
