Welcome to the State Water Resources Control Board Welcome to the California Environmental Protection Agency
Governor's Website Visit the Water Board Members Page
Agendas
My Water Quality
Performance Report

1,2,3,-Trichloropropane

Announcements

Current Status - Regulation of 1,2,3-TCP

Primary drinking water standards, or maximum contaminant levels (MCLs) are health protective limits that are applicable to drinking water served by public water systems. Currently, there is no federal MCL for 1,2,3-TCP. In the absence of a federal standard, California may establish its own drinking water standards.

Over the last several years, the Division of Drinking Water has received input from affected water systems expressing concerns about the lack of a drinking water standard for 1,2,3-TCP.  Local community groups and environmental justice groups have requested that the State Water Board set as one of its highest priorities the development of an MCL for 1,2,3-TCP.  In May/June 2016, the State Water Board held focused stakeholder meetings on the proposed regulation to establish an MCL for  1,2,3-TCP.  These meetings, which were held in Visalia, Bakersfield and Fresno, engaged representatives from public water systems whose drinking water supplies were affected by 1,2,3-TCP contamination. In July 2016, public workshops on the development of  a 1,2,3-TCP MCL will be held in Sacramento, Fresno, and Bakersfield.

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.

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 1999, 1,2,3-TCP was added to the list of chemicals known to the state to cause cancer.

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 to have been completed by the end of 2003. Some water systems continue their monitoring for 1,2,3-TCP.

SRL's methods, which were published in February 2002, have Environmental Laboratory Accreditation Program (ELAP) test method designations, Purge and Trap GC/MS (SRL 524M-TCP) and Liquid-Liquid Extraction GC/MS (SRL 525M-TCP), that are capable of 1,2,3-TCP quantification at the DLR. The two SRL methods and EPA Method 504.1 are certified by ELAP for Field of Testing 104, Volatile Organic Testing of Drinking Water. Click here for a current list of laboratories that are certified by ELAP for these methods (PDF).

Though monitoring for 1,2,3-TCP had occurred from 1989 through the 1990s under earlier UCMR regulations, fewer than 20 sources had reported detections. This likely reflected the less sensitive analytical method available at that time and the reporting limit of 0.5 μg/L.

Though the UCMR testing is no longer required, the Division of Drinking Water recommends -- when analyses for 1,2,3-TCP are performed -- that water systems' laboratories use the more sensitive analytical methods for 1,2,3-TCP, in order to enable better characterization of the presence of the chemical in drinking water sources.

The water quality monitoring database is available here.

Summary of 1,2,3-TCP Detections

Butte (04)

1

1

0

0

1

Fresno (10)

69

54

13

2

10

Kern (15)

151

76

71

4

20

Los Angeles (19)

155

95

19

41

15

Madera (20)

1

1

0

0

1

Merced (24)

26

7

12

7

11

Monterey (27)

1

1

0

0

1

Riverside (33)

22

20

2

0

4

Sacramento (34)

2

1

1

0

2

San Bernardino (36)

24

18

3

3

6

San Diego (37)

13

7

4

2

1

San Joaquin (39)

19

12

7

0

4

San Mateo (41)

11

9

2

0

3

Santa Cruz (44)

1

1

0

0

1

Stanislaus (50)

17

9

8

0

5

Tulare (54)

49

37

10

2

9

Total

562

349

152

61

94

*Sources with two or more reported detections, as of June 2016. "Sources" includes active and standby sources and may include either raw or treated drinking water wells and surface water sources, distribution systems, blending reservoirs, and other sampled entities. For this table, we've excluded inactive, abandoned and destroyed sources, agricultural sources, monitoring wells and sources with only a single detection

Note that, for this presentation, the same source may have been counted more than once (e.g., one source may have raw, treated, treatment point, distribution system or blending reservoir data entries).

Sources with two or More Reported 1,2,3-TCP Detections (Excel, 1.7MB)

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.



envelope  To receive email notices about upcoming drinking water regulations and other drinking water-related information, subscribe to our email lists (Click on the “Drinking Water” section).


(Updated 7/22/16)