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Chinese Dry Wall

Certain batches of dry wall imported from China contain high levels of sulfur compounds. Static in-chamber studies have shown that these dry wall samples emit carbonyl sulfide, carbon disulfide, hydrogen sulfide, and methyl mercaptan, among other sulfur containing compounds. When present in the atmosphere at “significant concentrations”, these compounds are highly toxic to animals and humans and target the central and peripheral nervous systems. These compounds smell badly even at extremely low concentrations; however, because you can smell these highly odiferous materials does not mean that they present any serious health risks at “odor threshold levels”. For example, methyl mercaptan is used in propane and natural gas so that the gases can be detected in the event of leakage.

One of the basic tenants of toxicology is, “the dose makes the poison”. A single aspirin may be helpful in soothing a headache, but a bottle of aspirin will result in serious health effects and even death. It may be unpleasant to smell these sulfur compounds, and under certain circumstances they may produce upper respiratory irritation, eye irritation, and exacerbate existing health conditions such as asthma. Truthfully, there is very little, if any, available scientific data aimed at studying the potential health effects of these materials at very low concentrations such as those assumed to be present in homes contaminated with Chinese dry wall. There is no available data to identify effects on unborn fetuses or neonates.

A recent report issued by the Consumer Product Safety Commision (CPSC) on November 23, 2009, described a study of 51 residences located in Florida, Louisiana, Virginia, Mississippi, and Alabama. In forty-one of the houses, residents complained of problems with dry wall. Ten houses in each neighborhood were non-complaint houses and used as controls. Sophisticated analytical techniques based mostly on strontium content were used on the dry wall samples to identify them for possible contamination. Copper and silver strips were exposed to indoor air to assess the potential for corrosion since both metals react with sulfides in the air, and the results correlated well with the analytical findings in identifying contaminated houses. Corrosion of electrical fixtures by low levels of airborne sulfur compounds is a serious problem, but this was not the focus of this dissertation.

Air sampling of suspect homes was carried out using passive air samples for hydrogen sulfide and carbon disulfide, two suspect materials that volatilize from Chinese dry wall samples. Hydrogen sulfide was found to be statistically higher in the contaminated homes than the control homes. Other components, including carbon disulfide, showed differences between contaminated homes and control homes, but the differences were not statistically significant. Formaldehyde was found in both control and contaminated homes at about the same concentration. Hydrogen sulfide, the most abundant sulfur compound measured in air, was found only at a median concentration of 0.59 parts per billion (ppb). The minimum reported threshold odor level for hydrogen sulfide is 0.5 ppb. Median concentrations of carbon disulfide were found to be 2.2 ug/m3 and 0.74 ug/m3 (micrograms per cubic meter of air) for complaint and non-complaint homes, respectively. This difference was not statistically significant. The odor threshold for carbon disulfide is between 62 and 310 ug/m3.

Health complaints, including upper airway, skin, and eye irritation, were common from some occupants. Both hydrogen sulfide and formaldehyde are known irritants at certain concentrations, but these concentrations were never found in any of the houses as indicated in the results of the CPSC study described above. For hydrogen sulfide, the inhalation reference concentration (RfC) is 1.4 ppb (2x10-3 mg/m3). A RfC is an estimate of a continuous inhalation exposure concentration to people (including sensitive subgroups) that is likely to be without risk of deleterious effects during a lifetime. For carbon disulfide, the RfC is 700 ug/m3. It seems obvious from this data that the levels of hydrogen sulfide and carbon disulfide are well below those known to produce health effects. In the CPSC report, several scenarios are proposed relating to the observed symptoms, but none are based in science.

There is no good scientific foundation in the literature describing health effects at the levels of contamination measured in houses contaminated by Chinese dry wall. Any claims of long-term health effects cannot be supported in the legal system, particularly in Federal Court. At the Chinese Dry Wall Conference entitled, “Chinese Dry Wall - Toxicity, Risk and Causation” held in New Orleans on November 11, 2009, Dr. Parent presented his findings, stated his position, and used the Hill Criteria to provide a causation analysis. Click the link below to view the Chinese Dry Wall slide presentation.

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