"Chinese drywall" refers to an environmental health issue involving defective drywall manufactured in China, imported to the United States and used in residential construction between 2001 and 2009 affecting "an estimated 100,000 homes in more than 20 states".
In samples of contaminated drywall, laboratory tests will detect off-gassing of volatile chemicals and sulfurous gases — including carbon disulfide, carbonyl sulfide, and hydrogen sulfide. The emissions worsen as temperature and humidity rise, will give off a sulfuric (rotten egg) odor and will cause copper surfaces to turn black and powdery, a chemical process indicative of a hydrogen sulfide reaction and an early indication of contaminated drywall. Copper pipes, electrical wiring, and air conditioner coils are affected, as well as silver jewelry.
Homeowners have reported health symptoms including respiratory problems such as asthma attacks, chronic coughing and difficulty breathing, as well as chronic headaches and sinus issues.
Background
Drywall, also known as plasterboard, is a building material typically consisting of gypsum-based plaster extruded between two thick sheets of paper and kiln-dried.
Drywall was imported by the United States during the construction boom between 2004 and 2007, spurred by a shortage of American-made drywall due to the rebuilding demand of nine hurricanes that hit Florida from 2004 to 2005, and widespread damage caused along the Gulf Coast by Hurricane Katrina in 2005.
An analysis covering drywall imports since January 2006 showed that more than of Chinese drywall was brought into the United States since then, enough to build 60,000 average-sized homes.
Homeowners alleging contaminated drywall have reported numerous incidents of corroding copper and other metals in their homes. The Florida Department of Health advised homeowners worried about tainted drywall to check copper tubing coils located in air conditioning and refrigeration units for signs of corrosion caused by hydrogen sulfide, as these are usually the first signs of the issue. Under normal circumstances, copper corrosion leaves it a blue/green or dark red color, whereas corrosion as a result of hydrogen sulfide exposure leaves a black ash-like corrosion. Homeowners who have verified that their home contains contaminated Chinese drywall are advised to replace any suspect drywall, as well as any potentially damaged copper electrical wiring, fire alarm systems, copper piping, and gas piping.
Affected locales
In the United States, most complaints have come from states in the Southeast, where a warm and humid climate seems to encourage the emissions. According to published reports, "Chinese drywall was used in the construction of thousands of homes, mainly in the South, after a series of hurricanes in 2005 and before the housing bubble burst."
The states of Florida (56%), Louisiana (18%), Mississippi (6%) and Alabama (6%) made up 86% of the 3,952 cases reported to the U.S. Consumer Product Safety Commission (CPSC) as of April 19, 2012. More than 700 complaints had been filed with the Florida Department of Health. Sources estimated that from 60,000 to 100,000 homes could be affected.
The CPSC has released a guide for identifying the symptoms of a home affected by the problem drywall.
Sources
Knauf Plasterboard Tianjin Co., Ltd., part of Knauf Gips KG, has been identified as a major producer of imported Chinese drywall. Though a number of other Chinese companies are believed to have produced defective drywall, Knauf's name comes up most frequently, because the company prints its name on its products. Much of the other contaminated drywall has no markings, making it difficult to identify its origin.
Dramatic increases in new home construction, coupled with the reconstruction effort after hurricane damage, led to a soaring increase in the quantity of imported Chinese drywall. Time magazine reported that more than of drywall was imported from China from 2006 to 2009, including much from the known principal manufacturer of the contaminated drywall, Knauf. However, domestic drywall manufacturing averages over per year, leaving imported Chinese drywall with only a small portion of the market. It is estimated that this imported drywall has been used to construct approximately 60,000 homes.
From January to September 2006, of Knauf drywall were unloaded in New Orleans, three-quarters of it from Knauf Tianjin, and at least of Knauf drywall was shipped directly from China to Florida ports.