Drywall, used in home construction, is a layer of gypsum sandwiched between two sheets of paper. Although most drywall is made in the United States, shortages during the last housing boom led to imports from China.
In addition, some of the drywall is made of synthetic gypsum made from a chemical process using lime or limestone and gas from coal-fired power plants. However, the smokestacks contain sulfur which must be removed from the synthetic gypsum.
Some Chinese experts in building materials believe flawed desulfurization methods were used.
Homeowners from around the United States who are living with contaminated drywall have complained of a rotten-egg smell, itchy eyes, runny noses, nosebleeds, headaches and asthma attacks. The contaminated drywall has also been linked to corroded pipes, wires and appliances.