Trichloroethylene (TCE) has been a familiar cleaning solvent for metal finishers for decades. Past and future use will be affected by a report made on July 27 to the U.S. Environmental Protection Agency (EPA) by the National Academyof Sciences and the National Academy of Engineering.
The report makes two recommendations: (1) for the EPA to complete a credible human health risk assessment to update the draft one it issued in 2001, and (2) for additional research be organized and funded to better understand the pathways by which TCE can cause cancer and other adverse health effects.
Prompted by the accumulation of animal research and human population studies, including a concern about kidney cancer in humans, the recommendation speaks to the need to extrapolate from these studies to an estimate of the cancer risk posed by TCE at low doses.
In other words, the exposure limit in air and the maximum concentration in drinking water of TCE are likely to change within a few years. Earlier in 2006, the American Congress of Governmental Hygienists (ACGIH) proposed an exposure limit in air of 10 ppm (to be set in 2007) vs. the current value set by the U.S. Occupational Safety and Health Administration (OSHA) of 100 ppm. In drinking water, the maximum concentration is currently set by the EPA at 5 ppb.
Available vapor degreasing equipment can allow use of TCE without causing employees to be exposed to more than the 10 ppm limit in air. But, change in the limit in drinking water is more significant – especially if your firm is responsible for clean up of sites where TCE was dumped to ground soil in the past. For example, this is of great concern to the U.S. Air Force who is liable for cleanup of the site of the former Kelly Air Force Base in San Antonio, Texas. Should the limit in drinking water be reduced to say 1 ppb, clean up costs now projectedto be several hundred million dollars would skyrocket.
You can learn more about the report at http://www.nas.edu/ and views from an industry group at http://www.hsia.org. Readers of Controlled Environments Magazine will be informed about actions associated with this report.
Contributed by John Durkee, Ph.D., P.E.