Amidst the Post-Katrina housing boom in the mid-2000s, a domestic shortage of drywall led the United States to import Chinese-manufactured drywall to meet demand. Only months after installation, homeowners who built or remodeled using imported Chinese drywall encountered sulfur-like odors, failed air conditioning systems, and blackened metal surfaces within their homes. Many affected property owners were left with significant repair costs and evolving remediation guidelines issued by the Consumer Product Safety Commission (CPSC). Identification of impacted drywall was also challenging because of the unknown nature and extent of the problem as well as the inconsistent labeling practices across Chinese manufacturers. U.S. national laboratories were called in to investigate the cause of the reported emissions. Early studies pointed to the presence of elemental sulfur in the gypsum core of the board as a reliable marker to identify drywall of concern, but the actual emission mechanism was never scientifically proven. Now, more than five years after the problem was discovered, President Obama has signed the Drywall Safety Act of 2012. Among other requirements of this law, U.S. manufacturers and importers will need to meet yet-to-be-determined CPSC standards for drywall that limit elemental sulfur content to “a level not associated with elevated rates of corrosion in the home.” Unfortunately, this language implies elemental sulfur, in and of itself, is the cause of the problem, a contention that to date has not been scientifically established. The observed behavior in the field and the chemical nature of elemental sulfur are also inconsistent with this implication. In its most recent Identification Guidance, CPSC acknowledged the need for further corroborating scientific evidence (e.g., corrosion chamber tests) for boards with greater than 10ppm elemental sulfur.
The passage of this law leaves the drywall industry in a precarious position. The creation of an industry-wide limit will require implementation of testing protocols to demonstrate compliance. What remains unclear is the scientific basis CPSC will use to set the U.S. industry-wide limit when its prior studies were based on complaints that stemmed from Chinese-manufactured product. Because the presence of elemental sulfur has only been scientifically established as a marker rather than the source of emissions, there also may be significant ramifications in establishing a limit that removes good product from the market or creates an artificial safety net that is not reliable outside of the parameters of the CPSC investigations to date.
The latest guidance by the CPSC (2011) on identification of problematic drywall is an elemental sulfur content of 10 parts per million (ppm). This number already poses an analytical challenge because drywall is composed of gypsum (calcium sulfate), so just measuring the total amount of sulfur in the drywall is extremely difficult even with sophisticated instrumentation. Available analytical methods have limits of detection between 1 and 10 ppm and they are considered expensive. If the level established by CPSC is at or below the limit of available techniques, manufacturers will have no ability to prove that elemental sulfur in their products is below the limit. Regardless of the level set by the CPSC, industry will need to find cost-effective technologies and solutions, such as field-deployable devices, to demonstrate compliance and mitigate significant cost increases to a commodity product.
The impact of this new law on the different industry segments is also unclear. Gypsum generally comes from two industrial sources: naturally mined gypsum and flue-gas desulfurization (FGD) gypsum, which is generated from the conversion of beds of limestone (calcium carbonate) in the smoke stacks of fossil-fuel power plants to gypsum (calcium sulfate) as the combustion gases pass over it. Depending on the source, the resulting gypsum material may have different impurities (tramp minerals or deposits) that may or may not contain elemental sulfur. Furthermore, many jurisdictions require that drywall be recycled, so companies will have a need to know that the material they are recycling does not exceed the established limit. The co-mingling in demolition debris of boards from multiple construction sites from multiple manufacturers makes sampling and testing protocols a challenge over and above that imposed by the limit set on the production and sale of new product.
The Drywall Safety Act of 2012 mandated action by the CPSC with an established timetable. To their credit, the CPSC has thus far relied upon the scientific evidence in formulating their guidance to the public. Sound scientific data should continue to guide CPSC’s determination of final analytical requirements. The window of opportunity to contribute and comment is narrow, but it is open. Despite a long history without sulfur-containing emissions problems, U.S. drywall manufacturers will now bear the brunt of this new requirement. As such, there are many critical issues that need to be addressed before implementation of this law. Industry, and ultimately the consumer, may suffer if sound science is mute in the discussion.