In August of 2008, the Environmental Protection Agency (EPA) was officially notified of the problem. After some investigation, the bulk of the tainted drywall was traced by to a manufacturer called Knauf Plasterboard Tianjin Co. Ltd. Initially, the company refused to take any blame and said that the toxic drywall came from another, unnamed company. But as the problem grew and testing began, the company acknowledged that it had shipped some of the bad drywall, but blamed a single gypsum mine in Tianjin, China, that's no longer being used. The drywall in question has been found to have significant levels of several chemicals believed to be responsible for the ill effects, including:
- Iron disulfide
- Hydrogen sulfide
- Sulfuric acid
- Sulfur dioxide
- Carbon disulfide
As of May 2009, testing was still underway on drywall sheets all over the United States, but mainly in Florida, Louisiana and a few other coastal states. However, the problem could be more widespread than initially thought, with recent statistics placing the toxic gypsum board in up to 100,000 homes in 41 states [source: PR Newswire]. One reason the coastal states, especially Florida, have been impacted the most is because it's believed that heat and humidity have exacerbated the vapors being emitted into the air.
Researchers aren't sure exactly what's caused the problem, but chemical fumigants used on the materials in the drywall may be the culprit. Another factor could be the use of a byproduct called fly ash that's less refined in China than it is in the United States. Fly ash has nothing to do with the buzzing pests -- it's a residue of coal combustion that's more typically used as an ingredient in concrete mixtures. In the United States, a process of scrubbing a coal mine's smokestack emissions creates the calcium sulfate, or gypsum, that's used to make drywall. Knauf Plasterboard Tianjin used fly ash before it ever reached the smokestack, making it less refined and highly suspect [source: Associated Press].