Saturday, April 25, 2009

Could multiple chemical exposures be the problem with Chinese Wallboard (Sheetrock)?

CNN, Wall Street Journal, Associated Press, and Indoor Environment Connections have all reported on the concern regarding imported Chinese Wallboard. It seems once the Chinese wallboard gets wet or damp it off-gases a rotten-egg stench made of sulfur-based gases. Homeowners claim these gases can corrode metals, and may cause headaches and aggravation of respiratory systems, such as asthma. Many of these reports quote health departments as saying that levels are not elevated enough to suggest an imminent or chronic health hazard. However, there should be a concern regarding the potential for multiple chemical exposures, their cumulative effect, and the potential for long exposures to low levels of the compounds on the occupants.

The Chinese wallboard problem may affect over 35,000 homes and so far, is in states with high humidity and temperature levels where homes were constructed or renovated between 2004 and 2008. These homes and buildings, because of the shortage of domestic wallboard (also called sheetrock, drywall, and gypsum board), were installing Chinese-imported wallboard (not all Chinese wallboard is a problem). Up until this point, the reports regarding the tests on the drywall, quoting one health department “has not identified data suggesting an imminent or chronic health hazard at this time.” Some reports actually say levels found in the affected homes are not elevated enough to be of concern. One report gave hydrogen sulfide levels of .05 to .07 parts per million (ppm). Another report detected “carbon disulfide levels of approximately 5 parts per billion – all samples were less than 15 parts per billion.” The same report also reported carbonyl sulfide in the same levels. Chamber testing of the Chinese wallboard emitted carbon disulfide, carbonyl sulfide, and hydrogen sulfide, while other tests of the wallboard found in addition sulfuric acid and sulfur dioxide. The Occupational Safety and Health Administration (OSHA), the National Institute of Occupational Safety and Health (NIOSH), or the Environmental Protection Agency (EPA) identifies all these compounds as toxic compounds. However, the levels found are below many of the standards used for worker exposure. This is the crux of the problem, the limitations of using worker exposure standards to evaluate indoor air quality have been known for a long time and a professional would use them with limitations, typically dividing them by a factor of 10 to 100. For example, the OSHA permissible exposure limit for carbon monoxide is 50 ppm, while the indoor air quality industry uses 5 ppm to 10 ppm as a guide for evaluating air quality in office buildings.

Exposure research is very limited when looking at exposures to multiple chemicals or to long term exposures to low levels of compounds. Since this research is so limited to the point of nonexistent it is hard to say what the impacts of multiple chemical exposures or long term low level exposures would be. The limited knowledge we have points to potential moderate or minimal effects on individuals based on the compounds they are exposed to. Exposure to the multiple sulfur gases for long periods or low levels could be causing the headaches; sore throats; repeated nose bleeds; breathing problems; respiratory infection; wheezing; sinus problems; and various other respiratory ailments that occupants have complained about. Our health departments should be erring on the side of health but too many times they side on convenience.

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