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.
Possible Solutions
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.
