1,2,3,-Trichloropropane (1,2,3 - TCP)

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Background

1,2,3- TCP is a chlorinated hydrocarbon with high chemical stability. It is a manmade chemical found at industrial or hazardous waste sites. It has been used as a cleaning and degreasing solvent and also is associated with pesticide products.

1,2,3-TCP causes cancer in laboratory animals (US EPA, 2009). It is reasonably anticipated to be a human carcinogen (NTP, 2014), and probably carcinogenic to humans, based on sufficient evidence of carcinogenicity in experimental animals (IARC, 1995). In 1992, 1,2,3-TCP was added to the list of chemicals known to the state to cause cancer, pursuant to California's Safe Drinking Water and Toxic Enforcement Act (Proposition 65)..

In 1999, we established a 0.005-micrograms per liter (μg/L) drinking water notification level for 1,2,3-trichloropropane (1,2,3-TCP). This value is based on cancer risks derived from laboratory animals studies (US EPA , 1997). The notification level is at the same concentration as the analytical reporting limit, as described below. Certain requirements and recommendations apply if 1,2,3-TCP is detected above its notification level.

The 1,2,3-TCP notification level was established after its discovery at the Burbank Operable Unit (OU) — a southern California Superfund hazardous waste site — because of concerns that the chemical might find its way into drinking water supplies. It had been found in several drinking water wells elsewhere in the state at that time. Subsequently 1,2,3-TCP was found in more drinking water sources

In 2001, to obtain information about the presence of 1,2,3-TCP in drinking water sources, we adopted a regulation that included it as an unregulated contaminant for which monitoring is required (UCMR). Given the number of sources with detections of 1,2,3-TCP under the UCMR sampling , the Drinking Water Program (now the Division of Drinking Water) considered this chemical to be a good candidate for future regulation. Thus, in July 2004 we requested a public health goal (PHG) from the Office of Environmental Health Hazard Assessment (OEHHA).

In September 2007, OEHHA released a draft PHG (0.0007 µg/L) and technical support document, and in January 2009, a revised draft technical support document. In August 2009, OEHHA established a 0.0007-µg/L PHG for 1,2,3-TCP

Monitoring Requirements, Analytical Methods, and Monitoring Results

For the UCMR monitoring, the Department of Public Health's Sanitation and Radiation Laboratories (SRL) -- now the Drinking Water and Radiation Laboratories (DWRL) -- developed protocols for analytical methods for 1,2,3-TCP at levels comparable to the notification level of 0.005 μg/L. Monitoring under the UCMR regulation was completed at the end of 2003. Some water systems continued their monitoring for 1,2,3-TCP.

The SRL method, which was published in February 2002, has Environmental Laboratory Accreditation Program (ELAP) test method designation, Purge and Trap GC/MS (SRL524M), is capable of 1,2,3-TCP quantification at the DLR. The SRL method is certified by ELAP for Field of Testing 104, Volatile Organic Testing of Drinking Water. The list of accredited laboratories for lab method SRL 524M can be found here. (Last Updated 1/31/18)

Though monitoring for 1,2,3-TCP had occurred from 1989 through the 1990s under earlier UCMR regulations, fewer source detections reflected the less sensitive analytical method available at that time and the reporting limit of 0.5 μg/L

 The water quality monitoring database is available here.

References

ATSDR, 2011. Addendum to the Toxicity Profile for 1,2,3-Trichloropane (PDF), Agency for Toxic Substances and Disease Registry, Centers for Disease Control, August 2011. Other information on 1,2,3-TCP from ATSDR is here.

IARC, 1995. 1,2,3-Trichloropropane (PDF), IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 63, Dry Cleaning, Some Chlorinated Solvents, and Other Industrial Chemicals, International Agency for Research on Cancer.

NTP, 2014. 1,2,3-Trichloropropane (PDF), in Report on Carcinogens, 13th Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, October.

OEHHA, 2009. Public Health Goal for 1,2,3-Trichloropropane in Drinking Water (PDF), August 2009.

US EPA, 1997. Health Effects Advisory Summary Tables (HEAST), FY 1997 Update, US Environmental Protection Agency, Solid Waste and Emergency Response, 9200.6-303 (97-1), EPA-540-R-97-036, July 1997.

US EPA, 2009. Toxicological Review of 1,2,3-Trichloropropane (PDF) in Support of Summary Information on the Integrated Risk Information System (IRIS), US EPA. September 2009. IRIS summary is here.

US EPA, 2014. Technical Fact Sheet – 1,2,3-Trichloropropane (TCP), Office of Solid Waste and Emergency Response, EPA-505-F-14-007. January 2014.

Additional Information

Information for Drinking Water Systems

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