Current Massachusetts Regulatory Limit
MMCL: 0.1 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase II rule (56 FR 3526, 1-30-91).
Federal Regulatory Limit
The MCL for total chromium is equal to its MCLG of 0.1 mg/L (56 FR 3526, 1-30-91).
Basis for Criteria
There are two forms of chromium that are of toxicological importance: chromium III and chromium VI. chromium VI is believed to be the form responsible for the carcinogenic responses seen when animals and humans are exposed to chromium by inhalation. Chromium III is oxidized to the VI valence state and is therefore, important for the overall assessment of the potential for adverse health effects. The MCL however is based on the potential for adverse non-cancer effects of chromium VI and is consistent with the National Research Council's recommended daily intake range of 50 to 200 ug per day. Information on human exposure to chromium was used to determine a relative source contribution of 0.71 for chromium in drinking water. The MCL was developed based on the RfD presented below, assuming that a 70 kg adult ingests 2 L/day of drinking water and that 0.71 of the total exposure to chromium is through drinking water (Fed Reg, 1985).
RfD: 5 x 10-3 mg/kg/day
UF: 500 (5 = an additional safety factor for less than lifetime exposure of the principal study; 10 = intraspecies; 10 = interspecies)
Confidence in RfD: Low
Groups of eight male and eight female Sprague-Dawley rats were supplied with drinking water containing 0-11 ppm (0-11 mg/L) hexavalent chromium for 1 year (McKenzie et al, 1958). No significant adverse effects were seen in appearance, weight gain or food consumption, and there were no pathological changes in the blood or other tissues in any treatment groups. A NOAEL of 2.41 mg/kg/day was identified from this study.
A - inhalation/D - ingestion.
Through inhalation studies, dose-response relationships have been established for chromium exposure and lung cancer. These relationships were established from occupational epidemiological studies of exposed workers. Only chromium VI is classified as a human carcinogen. There is no definitive evidence for the carcinogenicity of chromium VI by ingestion.
200.7A (inductively coupled plasma)
U.S. EPA 218.2 (A.A.1 Furnace Technique)
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. November 13, 1985. Part IV. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations; Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms; Proposed Rule. (50 FR 46936).
Federal Register. May 22, 1989. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary and Secondary Drinking Water Regulations; Proposed Rule. (54 FR 22062).
Federal Register. January 30, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Final Rule. (56 FR 3526).
MacKenzie, R.D., R.U. Bierrum, C.F. Decker, C.A. Hoppert and R.F. Langham. 1958. Chronic Toxicity Studies. II. Hexavalent and trivalent chromium administered in drinking water to rats. Am. Med. Assoc. Arch. Ind. Health. 18:232-234.
U.S. EPA (U.S. Environmental Protection Agency). October 19, 2001. Toxicological review of chloroform (CAS No. 6766-3) - in support of summary information on the Integrated Risk Information System. EPA/635/R-01/001.