What is carbon disulfide? Is it associated with natural gas production?

In discussions about air quality studies, carbon disulfide is occasionally mentioned as a detected compound.  The EPA describes carbon disulfide as a clear, colorless or faintly yellow liquid at room temperature. It is not associated with the production of natural gas in the Barnett Shale.  A more complete discussion of carbon disulfide by Dr. Janet Kester, Ph.D., D.A.B.T here.

Following are a few summary points:

· Carbon disulfide is released into the environment naturally from a side variety of natural sources:  soils, marshes and coastal regions tend to be the largest biogenic sources.  According to the World Health Organization, 40% and possibly 80% of releases are a result of natural and biogenic activity (Concise International Chemical Assessment Document 46, Carbon Disulfide,WHO 2002).

· Carbon disulfide is also released from some industrial processes such as the production of viscose rayon fibers.  It is also used in the production of carbon tetrachloride and cellophane. Carbon disulfide is used as a solvent for rubber, sulfur, oils, resins and waxes and has been used for soil fumigation and insect control in stored grain.  Several industrial processes produce carbon disulfide as a by-product, including coal blast furnaces and oil refining.  Carbon disulfide is also present in cigarette smoke.

· The concentrations of carbon disulfide measured in U.S. ambient air (24-hour samples) in 2009 averaged 0.34 ppb, and ranged up to 41.4 ppb. In comparison, the range of 24-hour carbon disulfide concentrations reported in the Interim Ambient Air Monitoring Report of the City of Fort Worth Natural Gas Air Quality Study was 0.008 to 1.64 ppb, with an average of 0.24 ppb. Thus, the concentrations measured in Fort Worth appear to be lower than the national average data.

· Chronic toxicity values for carbon disulfide exposure via inhalation have been developed by several agencies based on effects on the nervous system observed in occupational epidemiological studies.  Risk levels range from the ATSDR value of 300 ppb to the OSHA permissible exposure level of 20,000 ppb.

· A newspaper article concerning a yet-to-be-released study performed by the Fort Worth League of Neighborhoods stated “League investigators reported using a standard set by OSHA to gauge the occupational risk of exposure to carbon disulfide.  The findings were several times higher than OSHA’s short-term health benchmark for adults,” the report stated.  While we can only speculate as to both the concentrations measured in this study and the identity of the “healthbenchmark” referred to in this article, it is interesting to note that OSHA’s acceptable 30-minute peak concentration for carbon disulfide is 30,000 ppb, and its maximum peak concentration is 100,000 ppb. “Several times higher” than these values would thus be perhaps 90,000 to 300,000 ppb, thousands of times higher than the highest concentration measured anywhere in the U.S. in 2009, and tens to hundreds of thousands of times higher than the highest concentration reported to date from the City of Fort Worth study.