Chinese Drywall – Key Scientific Questions
Ed Light, CIH – Building Dynamics – BHS/BD Team
Chinese drywall is rapidly emerging as a complex and unprecedented indoor environmental issue lacking obvious solutions. Research is needed to identify and systematically address critical questions as quickly as possible to support an intelligent response and practical solutions.
In the past, the basic science for other indoor environmental concerns was sufficiently understood to develop cost-effective solutions which protected the health of those exposed. In contrast, critical parameters with respect to Chinese Drywall have yet to be characterized and, as a result, the actions taken to date have been based simply on pure speculation.
At present, the best available data indicate the involvement of sulfide-contaminated drywall limited to some of the product imported from China. While it has been tentatively associated with odor and corrosion, health effects remain uncertain. The fundamental issue which ultimately must be determined by government and the courts is, “Who is responsible?” Determination of the success of any response measures will be based upon resolution of the damage and a fair distribution of costs.
Key scientific questions still requiring answers are:
- What is the actual chemistry? Product contamination has to be better defined, along with an understanding of the mechanism by which harmful by-products are released. In impacted spaces, the unique characteristics of the air quality have yet to be quantified. The potential for nearby materials acting as a sink and later emitting corrosive gasses, even after the original drywall is removed, has not been evaluated.
- What are the factors controlling environmental release and corrosion? Moisture and product loading are critical variables apparently increasing the risk of corrosion in sub-tropical climates and in building applications subject to elevated relative humidity. Other possible variables, including bacterial, also need to be examined.
- Is occupant health affected? Complaints reported thus far are largely non-specific symptoms coinciding with drywall-related odors. Preliminary toxicological analysis, based on the toxicology of measured pollutant concentrations, has been negative. However, because the mix of air contamination is likely to be complex and unstable, assessment based solely on levels of individual pollutants may not reflect risk. In addition, past experience has demonstrated that health impacts of indoor contaminants are often limited to sensitive individuals and cannot be predicted from dose/response of the general population.
- Is there a practical means of measuring exposure? As stated above, air contamination related to Chinese Drywall probably represents a complex, unstable and variable mixture, creating a moving target which is difficult to quantify. Sensitive analytical methods for sulfides are generally expensive and time-consuming. Widespread assessment, as is needed in a situation of this magnitude, will require a relatively inexpensive test procedure. Similarly, rapid development of effective controls depends upon the ability to make relatively simple measurements under a variety of conditions.
- Where Chinese Drywall is installed, how can exposure be minimized? Efficacious and cost-effective intervention might be achieved by controlling moisture and/or moisture migration, applying a scavenger or sealant, or pressurization controls. Measures based on air cleaning or ventilation might not be as cost effective. Temporary removal from the building may need to be considered for particularly susceptible individuals, if causation of a medical condition is established.
- When does Chinese Drywall need to be removed and how should this be done? Replacement of the affected drywall is the most costly option, especially when related systems and utility work is considered. An objective determination requires a risk assessment based on a more complete understanding of the underlying chemistry and molecular dynamics. Experience with other odor control problems suggests that contaminants adsorbed in adjacent materials may continue to off gas after the original source is removed. This needs to be considered in finalizing any Chinese Drywall replacement procedure.
- How can corrective measures be verified? As research progresses in those previously-discussed areas, reasonable criteria must be set which can be measured by a relatively simple procedure, necessarily conducted under standardized procedures. Such a guided methodology would permit confirmation that acceptable conditions have been attained by the remediation process.
Although research is in its early stages, now is the time to propose hypotheses and the potential cost of any proposed actions. Developing practical answers in the near future will require prioritized research which is focused upon answering the most important questions. In this context, the BHS/BD team suggests the following ideas for consideration:
- Based on preliminary findings, categorize buildings with Chinese Drywall with respect to apparent susceptibility to corrosion: low, moderate or high risk.
- Develop a screening tool to identify suspect drywall in place. Two possible methods might be ones based on colorimetric reaction or electrical conductivity.
- Develop a simple test as a general indicator of air corrosivity. One possibility might be a passive dosimeter measuring copper corrosion.
- Screen health complaints following a differential diagnosis approach.
- Conduct a preliminary epidemiological study, generally categorizing buildings by potential for Chinese Drywall emissions and medically verifying acute symptoms.
- Develop a list of potential control measures for evaluation based on building science and past experiences resolving other sources of indoor air contamination.
Future blogs will continue to address related issues, including lessons learned from previous indoor issues and a critique of Federal research efforts.