Tetrachloroethylene (PCE)

What is Tetrachloroethylene (PCE):

Tetrachloroethylene (PCE) is a volatile organic solvent commonly used in dry cleaning, textile processing, and as a degreasing agent since the 1930s.  PCE is still in use today in various commercial and industrial facilities across the United States.  PCE is nonflammable, clear, colorless, and has a sweet odor that is volatile and readily evaporates at room temperature (USEPA, 2012). Common names for PCE include perchloroethylene, perc, perchlor, and perclene. 

How Are Humans Exposed To PCE:

Humans can be exposed to PCE through multiple exposure pathways including inhalation, ingestion, and dermal contact.  Human exposure to PCE is most common through occupational sources such as working in a dry cleaning facility or textile facility where PCE vapors can be inhaled or transmitted through dermal contact to PCE during common tasks and machine maintenance (NYSDH, 2003).  New industry practices coupled with innovations in technologies have decreased the potential for PCE exposure in occupational exposure scenarios in the past decades (USEPA, 2012).  

Humans can also be exposed to PCE through environmental sources when PCE from commercial or industrial practices leach into soil and groundwater.  PCE is a long-lived chemical compound, does not degrade quickly, and can remain in the subsurface environment for decades. PCE can be ingested when PCE impacted groundwater enters potable water wells and is consumed. Soil and groundwater containing PCE contamination can release vapors which have the potential to enter indoor air of buildings leading to inhalation exposure in humans.  This process is known as vapor intrusion which is defined as the migration of volatile chemicals from the subsurface into overlying buildings (USEPA, 2015). Vapor intrusion in the past decade has become a forefront concern when evaluating potential exposures of PCE contaminated sites.       

What Are The Risks of PCE Exposure:

The health risks of exposure to PCE depend primarily on the concentration, duration, and frequency of exposure (PHDMD, 2012). Short-term exposure to PCE can cause central nervous system symptoms such as dizziness, headache, sleepiness, lightheadedness, and poor balance (ASTDR, 2014), (NIOSH, 2012).

Long-term exposures to PCE have shown associations with reducedscores on neurobehavioral or color vision tests, indicators of liver or kidney damage, reduced red blood cells, and blood and immune systems effects although the duration of the effects are no known (NIOSH, 2012).   Epidemiologic studies by the administration of PCE through multiple exposure pathways to laboratory mature rats and mice suggested evidence of carcinogenicity of PCE (JISA, 1993), (NTP, 1986). The National Institute for Occupational Safety and Health (NIOSH) has designated PCE as a “potential occupational carcinogen.” The United States EPA (USEPA) has designated PCE as “likely to be carcinogenic in humans by all routes of exposure” (USEPA, 2005).  

Is PCE Regulated:

PCE is subject to government regulations and standards designed to limit the exposure and potential adverse health effects in humans.  The table below provided via the Agency for Toxic Substances & Disease Registry (ASTDR) provides current regulatory levels for PCE (ASTDR, 2014).  

*ppm: parts per million; ppb: parts per billion. †TLV/TWA (threshold limit value/time-weighted average): time-weighted average concentration for a normal 8-hour workday or 40-hour workweek to which nearly all workers may be exposed. ‡STEL (short-term exposure limit): usually a 15-minute sampling period. §PEL (permissible exposure limit): highest level, averaged over a normal workday, to which a worker may be exposed. Table Courtesy of ASTDR, 2014.

*ppm: parts per million; ppb: parts per billion.

TLV/TWA (threshold limit value/time-weighted average): time-weighted average concentration for a normal 8-hour workday or 40-hour workweek to which nearly all workers may be exposed.

STEL (short-term exposure limit): usually a 15-minute sampling period.

§PEL (permissible exposure limit): highest level, averaged over a normal workday, to which a worker may be exposed.

Table Courtesy of ASTDR, 2014.

References:

1.       Agency for Toxic Substances & Disease Registry (ASTDR). ToxFAQs for Tetrachloroethylene (PERC). Atlanta, GA. December, 2014. http://www.health.ny.gov/environmental/chemicals/tetrachloroethene/index.htm 

2.       Japan Industrial Safety Association (JISA). Carcinogenicity Study of Tetrachloroethylene by Inhalation in Rats and Mice. Hadano, Japan. 1993. https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/630653

3.       National Institute for Occupational Safety and Health (NIOSH). Occupational Cancer – Carcinogen List. May, 2012. http://www.cdc.gov/niosh/topics/cancer/npotocca.html

4.       National Toxicology Program (NTP). Toxicology and Carcinogenisis Studies of Tetrachloroethylene (perchloroethylene) (CAS no. 127-18-4) in F344/N rats and B6C3F1 mice (inhalation studies). U.S. Department of Health and Human Services, Research Triangle Park, NC. 1986. https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/632655

5.       New York State Department of Health (NYSDH). Fact Sheet – Tetrachloroethylene (perc) in Indoor Air and Outdoor Air. 2003. http://www.health.ny.gov/environmental/chemicals/tetrachloroethene/index.htm

6.       Public Health Department – Madison & Dane County (PHDMD . An Overview of PCE Contamination of Indoor Air from Vapor Intrusion. Madison, WI: September, 2012. https://www.publichealthmdc.com/documents/PCEVaporIntrusionReport.pdf  

7.       U.S. Environmental Protection Agency (USEPA). Technical Guidance for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. Washington, D.C.: Office of Solid Waste and Emergency Response. June, 2015. https://www.epa.gov/sites/production/files/2015-09/documents/oswer-vapor-intrusion-technical-guide-final.pdf  

8.       U.S. Environmental Protection Agency (USEPA). Tetrachloroethylene (Perchloroehtylene) Hazards Summary. April 1992, Revised December, 2012. https://www3.epa.gov/airtoxics/hlthef/tet-ethy.html  

9.       U.S. Environmental Protection Agency (USEPA). Guidelines for Carcinogenic Risk Assessment. (EPA/630/P-03/001F). Washington, D.C.  March, 2005. https://www.epa.gov/risk/guidelines-carcinogen-risk-assessment