TCE and PCE Stories

The persistence in the marketplace of chlorinated solvents such as TCE (trichloroethylene) and PCE (perchloroethylene) is astonishing. One would have thought that the liabilities of soil and groundwater contamination, known health risks to workers, questions about health risks to the general public, burdensome regulations related to hazardous waste, air toxics and ozone depletion and the availability of alternatives, would have been more effective in phasing these chemicals out of the market.

The notable point about TCE and PCE from the viewpoint of environmental health is that their use patterns lead to widespread human exposure. A primary use for TCE and PCE are for solvent cleaning. Half of all PCE use is for dry-cleaning clothes. This means that TCE and PCE uses cut across a large number of industry and workplaces. NIOSH has estimated that approximately 390,000 workers are potentially exposed to TCE nationwide, and that approximately 690,000 workers are potentially exposed to PCE, based on the National Occupational Exposure Survey (NOES). While the NOES was completed over 20 years ago, and there hasn’t been an update, these numbers are likely to be reasonably consistent today. Chlorinated solvent use appears to have declined over time (trends for the U.S. have been hard for me to find – if I uncover more information, I’ll post it), but it is likely that a lot of these solvents are still sold. Occupational exposure is the most significant human health concern with TCE and PCE exposure (a topic for another day – I’ll be writing a number of posts on these chemicals).

Every day, millions of people bring home clothes from the dry cleaners that are off-gassing PCE. Dry-cleaned clothes represent one of the largest sources of exposure to PCE by the general public (see “Everyday Exposure to Toxic Pollutants”, by Wayne Ott and John Roberts, February 1998 Scientific American, downloaded for a price from sciam.com). This is consistent with a wealth of studies (most recently here) indicating that a preponderance of volatile organic compound exposure occurs indoors.

According to the ATSDR, over 1,309 Superfund sites in the U.S. have soil or groundwater that is contaminated with PCE; 1,460 Superfund sites are contaminated with TCE. This does not include thousands of other sites under the jurisdiction of state agencies and undergoing cleanup as part of RCRA Corrective action, which are not listed on the National Priority List. TCE exposure at contaminated sites is of sufficient concern that ATSDR has established a TCE subregistry within its National Exposure Registry.

In many cases, people living near these sites have been exposed to these chemicals in domestic-use water, from ingestion, skin contact or inhaling chemicals that volatilize from water. However, what has become a greater concern is vapor intrusion, a pathway where these chemicals volatilize from soil or groundwater, migrate through soil near building foundations and are drawn into indoor air through egresses in foundations. This issue took regulatory officials a bit by surprise, and has been a growing issue for hazardous waste site cleanups across the U.S. In New York, state officials are going to revisit 400 sites that had cleanup decisions made before 2003 to investigate the potential for indoor exposures to volatile compounds from vapor intrusion (this comes from the TCE Blog, your source for all things related to chlorinated solvents in the environment).

As you can imagine, there’s much more to this story, beyond the fact that TCE and PCE exposures are widespread. Who needs to be concerned about potential exposures? Under what conditions could people be at significant health risks? What can they be doing to reduce their risks? What can other stakeholders, such as governments and industries, be doing to reduce health risks from these chemicals? How do the potential risks from TCE and PCE exposure compare with other chemicals in a person’s environment?

Stay tuned for more posts on this topic. Until then, check out TCE Blog.