Update: August 1993
Current Massachusetts Regulatory Limit
MMCL = 0.07 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase V rule (57 FR 31776: 7-17-92).
Federal Regulatory Limit
The MCL for 1,2,4-trichlorobenzene is equal to its MCLG of 0.07 mg/L.
Basis for Criteria
The MCLG is based on the RfD presented below and assumes that a 70 kg adult ingests 2 L/day of drinking water. A relative source contribution factor of 20% is incorporated into the final value.
RfD: 0.01 mg/kg/day
UF: 1000 (10 = interspecies; 10 = intraspecies; 10 = lack of chronic studies)
MF: 1 Confidence in RfD: Medium
Acute exposure to 1,2,4-trichlorobenzene for relatively short periods of time at levels above the MCL could result in changes in liver, kidneys and adrenal glands. Chronic lifetime exposure to concentrations above the MCL may result in increased adrenal gland weights.
In multi-generation reproductive study, rats were given 0, 25, 100 and 400 ppm 1,2,4-trichlorobenzene added to drinking water for 95 days per generation for two generations, and F1 offspring were examined. A compound-related significant increase in adrenal gland weights was seen in P0 and F1 generations. Increased adrenal weights were associated with the histopathologic lesion, vacuolization of the zona fasciculata of the cortex. A NOAEL of 100 ppm (14.8 mg/kg/day) was identified from this study.
Cancer Assessment D
There is presently no evidence that 1,2,4-trichlorobenzene has the potential to cause cancer from a lifetime exposure in drinking water. The U.S. EPA has classified this chemical as a D carcinogen (not classifiable as to human carcinogenicity based on inadequate data) under the 1986 Carcinogen Risk Assessment Guidelines.
PQL: 0.0005 mg/L
U.S. EPA Methods 502.2; 524.2
PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at http://www.epa.gov/safewater/methods/methods.html
Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:
Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf
RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.
Federal Register. July 25, 1990. Part II. Environmental Protection Agency. 40 CFR Part 141 et al.. National Primary and Secondary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Proposed Rule.
Federal Register. July 17, 1992. Part III. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Synthetic organic Chemicals and Inorganic Chemicals; Final Rule. (57 FR 31776).