Update: August 1993
Current Massachusetts Regulatory Limit
MMCL = 0.007 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 is based on the MCLG of 0.007 mg/L.
Basis for Criteria
The MCLG is derived based on the RfD presented below and assuming that a 70 kg adult ingests 2 L/day of drinking water. A relative source contribution factor of 20% is incorporated in the final value.
RfD: 1 x 10-3 mg/kg/day (US EPA, 1989)
UF: 1000 (10 = interspecies; 10 = intraspecies; 10 = Lack of NOAEL in repro. study)
MF: 1 Confidence in RfD: low
The RfD is based on a two-year dietary study in rats in which groups of 60 rats/sex were fed dinoseb at 0, 1, 3 or 10 mg/kg/day in the diet. Effects included hunched appearance and staining of fur, polypnea and lower mean body weight gains. A statistically significant decrease in mean thyroid weight at all dose levels tested in male rats was also seen as well as a dose-related trend in decreased thyroid weight. A LOAEL of 1 mg/kg/day was identified from this study (Fed Reg 1990, 1992). The LOAEL was also supported by a 100-week mouse study (Brown, 1981as cited by Fed Reg, 1992) and a 3-generation reproductive study in rats (Irvine, 1981 as cited by Fed Reg, 1992).
The cancer classification for dinoseb is based on the lack of positive tumor data, in three rodent studies.
PQL: 0.002 mg/L
U.S. EPA 508; GC/ECD
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. (55 FR 30370)
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).
U.S. EPA (United States Environmental Protection Agency). August 1, 1989. Integrated Risk Information System (IRIS). U.S. Environmental Protection Agency. Washington, D.C.