Comment submitted by Tom McKee, Interfaith Community Organization

Dear USEPA IRIS: The overall confidence in this oral RfD assessment for hexavalent chromium has been rated " low" by the current IRIS with good reason. Confidence in the obsolete study relied upon by IRIS is low because of the small number of animals tested, the small number of parameters measured, and the lack of toxic effect at the highest dose tested. New more definitive studies have been published and are listed below. Please update the Oral RfD for Hexavalent Chromium based on these studies as soon as possible since this important parameter has been poorly regulated for decades. Tom McKee redknot@comcast.net National Toxicology Program Toxicity Report Series Number 72 *1. Sodium Dichromate Dihydrate (CAS No. 7789-12-0) Administered in Drinking Water to Male and Female F344/N Rats and B6C3F1 Mice and Male BALB/c and am3-C57BL/6 Mice - January 2007 * John R. Bucher, Ph.D., Study Scientist, National Toxicology Program, Post Office Box 12233, Research Triangle Park, NC 27709 NIH Publication No. 07-5964, National Institutes of Health, Public Health Service, U.S. Department of Health and Human Services Abstract Under the conditions of these 2-year drinking water studies there was clear evidence of carcinogenic activity of sodium dichromate dihydrate in male and female F344/N rats based on increased incidences of squamous cell neoplasms of the oral cavity. There was clear evidence of carcinogenic activity of sodium dichromate dihydrate in male and female B6C3F1 mice based on increased incidences of neoplasms of the small intestine (duodenum, jejunum, or ileum). *2. Cancer Mortality in a Chinese Population Exposed to Hexavalent Chromium in Drinking Water.* *Toxic Metals* Epidemiology. 19(1):12-23, January 2008. /Beaumont, James J. *; Sedman, Richard M. *; Reynolds, Stephen D. +; Sherman, Claire D. *; Li, Ling-Hong *; Howd, Robert A. *; Sandy, Martha S. *; Zeise, Lauren *; Alexeeff, George V. * / * Abstract:* Background: In 1987, investigators in Liaoning Province, China, reported that mortality rates for all cancer, stomach cancer, and lung cancer in 1970-1978 were higher in villages with hexavalent chromium (Cr+6)-contaminated drinking water than in the general population. The investigators reported rates, but did not report statistical measures of association or precision. Methods: Using reports and other communications from investigators at the local Jinzhou Health and Anti-Epidemic Station, we obtained data on Cr+6 contamination of groundwater and cancer mortality in 9 study regions near a ferrochromium factory. We estimated: (1) person-years at risk in the study regions, based on census and population growth rate data, (2) mortality counts, based on estimated person-years at risk and previously reported mortality rates, and (3) rate ratios and 95% confidence intervals. Results: The all-cancer mortality rate in the combined 5 study regions with Cr+6-contaminated water was negligibly elevated in comparison with the rate in the 4 combined study regions without contaminated water (rate ratio = 1.13; 95% confidence interval = 0.86-1.46), but was somewhat more elevated in comparison with the whole province (1.23; 0.97-1.53). Stomach cancer mortality in the regions with contaminated water was more substantially elevated in comparison with the regions without contaminated water (1.82; 1.11-2.91) and the whole province (1.69; 1.12-2.44). Lung cancer mortality was slightly elevated in comparison with the unexposed study regions (1.15; 0.62-2.07), and more strongly elevated in comparison with the whole province (1.78; 1.03-2.87). Mortality from other cancers combined was not elevated in comparison with either the unexposed study regions (0.86; 0.53-1.36) or the whole province (0.92; 0.58-1.38). Conclusions: While these data are limited, they are consistent with increased stomach cancer risk in a population exposed to Cr+6 in drinking water. (C) 2008 Lippincott Williams & Wilkins, Inc. http://www.epidem.com/pt/re/epidemiology/abstract.00001648-200801000-00004.htm;jsessionid=HpLhTQPKFnhLGQ2wtpHMvDqh3p2SdNbXlcrxHzG30zQn2W7JVrvP!1609592453!181195628!8091!-1 *3. Hexavalent Chromium, Yellow Water, and Cancer: A Convoluted Saga.* *Toxic Metals* Epidemiology. 19(1):24-26, January 2008. / Smith, Allan H. / * Abstract:* In this issue, Beaumont et al report cancer mortality rates associated with exposure to high concentrations of hexavalent chromium in well water in Liaoning Province, China. Contamination of drinking water at these levels has been reported only once before, among a small group in Mexico. The investigation in China is a convoluted tale. The first report indicated an increase in cancer mortality, while a subsequent publication with the same lead author claimed no increased risks. In 2006, the journal publishing the latter paper retracted it because of failure to disclose financial and intellectual input to the paper by outside parties (linked to chromium polluting industries). Beaumont and his colleagues now provide a further reanalysis of these data, showing increased mortality in particular from stomach cancer, but with serious limitations in the data and methods of analysis. These limitations are counterbalanced by the importance of a study of perhaps the highest exposure to hexavalent chromium in water that will ever be experienced by a population large enough to estimate risks of cancer. (C) 2008 Lippincott Williams & Wilkins, Inc.