Ding, the geoscientist who has worked as a consultant in China's gypsum industry for about 30 years, said some manufacturers began experimenting with phosphogypsum at the start of the decade. He said some drywall plants in China were now using 50% phosphogypsum as a base for plasterboard, others as much as 100%.
Some people in China liken the practice of mixing phosphogypsum in drywall to the recent scandals involving melamine, the industrial chemical that contaminated Chinese baby formula and animal feed.
Amid such heightened product-health concerns, officials at China's quality watchdog agency have been investigating complaints about Chinese-made drywall in the U.S., demanding that manufacturers submit samples for analysis, according to company executives.
But the agency has not issued any public statement on the probe, and officials did not respond to repeated requests for interviews.
In the U.S., federal authorities said there was no one authority responsible for ensuring that imported drywall meets American standards.
Consumer Product Safety Commission spokesman Joe Martyak said his agency asks U.S. Customs and Border Protection to inspect items for which there are mandatory testing requirements, such as children's toys. But there are no such conditions for drywall, he said.
In interviews, officials with U.S. Customs, the Environmental Protection Agency and the Department of Commerce all said their agencies were not responsible for testing drywall. That may reflect the fact that imported drywall is a relatively new phenomenon -- the U.S. used to have more than enough from its own sources, made with gypsum from mines or synthetic gypsum derived from coal combustion.
Waste byproduct is available, cheap
But in China, businesses began turning to phosphogypsum, in part because local governments were eager to get rid of bulging stockpiles of the waste byproduct.
Huge phosphogypsum dump sites can be seen in all corners of China. Near the banks of the Yangtze River in central China's Wuhan area, raw phosphogypsum is spread over 20 acres and packed 65 feet deep into the ground. The smell of sulfur permeates the air. Workers at the site said the material was given away to anyone willing to pay the transportation costs, a mere $1.75 per ton.
No one knows how much phosphogypsum board from China was shipped abroad. But in 2006, Chinese exports of drywall to the U.S. totaled a record 503 million pounds valued at more than $25 million, according to Chinese customs' statistics. That's enough for 32,000 homes.
