Introduction

Statutorily, the Office of Environmental Health Hazard Assessment (OEHHA) is required to perform a risk assessment, and to develop and publish a public health goal (PHG), based exclusively on public health considerations, for contaminants that have, or are proposed to have, drinking water standards (maximum contaminant level, MCLs).

Statutorily, OEHHA bases PHGs exclusively on public health considerations, and uses current principles, practices, and methods of risk assessment, and currently available data. Furthermore, to the extent that scientific data are available, the PHG is to take into account synergistic effects, effects of the contaminant on sensitive subgroups (including infants, children, pregnant women, individuals with a history of serious illness, and other subpopulations that are at a greater risk), and additive effects of the contaminant in media other than drinking water. If adequate scientific evidence is available, a threshold may be identified.

Statutorily, MCLs for drinking water contaminants are adopted as regulations by the Department of Health Services (DHS). An MCL for a contaminant is required to be established at a level that is as close as technologically and economically feasible to the corresponding PHG, placing primary emphasis on the protection of public health.

DHS, in its regulatory capacity, serves as the risk manager for contaminants in drinking water, while OEHHA is the risk assessor.

One contaminant for which DHS plans to adopt an MCL is chromium-6. (Chromium-6 is currently regulated as total chromium, a combination of chromium-3 and chromium-6.) Consistent with the provisions of the Statute, OEHHA will be developing a PHG for chromium-6, which may include an evaluation of the carcinogenic risk of the chemical.

Purpose of the Committee

The purpose of the Committee is to present written recommendations, and their scientific basis, to the Director of OEHHA, on the questions below regarding the potential carcinogenic risks of chromium-6 in drinking water, based on an evaluation of the scientific literature and exclusively on public health considerations as described in the introduction. OEHHA will consider these recommendations in developing a chromium-6 PHG.

The Evaluation Will Focus on the Following Questions:

1) Considering the toxicology, epidemiology and mechanistic information available regarding chromium-6, should chromium-6 be considered as posing a carcinogenic risk by the oral route?

2) If chromium-6 is to be considered as posing a carcinogenic risk by the oral route, what approaches does the Committee suggest to establish a PHG?

· The Borneff et al., (1968) mouse study is the only animal drinking water study of which we are aware that was designed to look at the potential carcinogenic effects of chromium-6. We are seeking your comments on the strengths and weaknesses of this study for purposes of making a quantitative estimate of the cancer risk for chromium-6 in humans.

· Does the epidemiology literature contain studies that would be useful to derive a cancer potency for chromium-6, such as, using the occupational data reporting excess gastrointestinal or other non-respiratory tumors?

· If the available literature does not allow the development of a cancer potency factor, what studies are available that would allow the development of a PHG that could take into account potential cancer risks from chromium-6. For example, some agencies apply an additional safety factor to the non-cancer chronic health effects observed in animals.

3) The conversion of chromium-6 to chromium-3 by simple chemical reactions in the stomach and pharmacokinetics after absorption can influence the toxic effects of chromium-6.

· How can the effects be quantified and the results applied as part of the approach in developing a PHG? As examples:

(1) Change the slope of the dose-response curve;

(2) Change the shape of the dose-response curve.

· Is there literature that indicates variability in the general population in the conversion of chromium-6 to chromium-3?

· Is there adequate information to identify a threshold for the oral route of exposure?

Introduction

Statutorily, the Office of Environmental Health Hazard Assessment (OEHHA) is required to perform a risk assessment, and to develop and publish a public health goal (PHG), based exclusively on public health considerations, for contaminants that have, or are proposed to have, drinking water standards (maximum contaminant level, MCLs).

Statutorily, OEHHA bases PHGs exclusively on public health considerations, and uses current principles, practices, and methods of risk assessment, and currently available data. Furthermore, to the extent that scientific data are available, the PHG is to take into account synergistic effects, effects of the contaminant on sensitive subgroups (including infants, children, pregnant women, individuals with a history of serious illness, and other subpopulations that are at a greater risk), and additive effects of the contaminant in media other than drinking water. If adequate scientific evidence is available, a threshold may be identified.

Statutorily, MCLs for drinking water contaminants are adopted as regulations by the Department of Health Services (DHS). An MCL for a contaminant is required to be established at a level that is as close as technologically and economically feasible to the corresponding PHG, placing primary emphasis on the protection of public health.

DHS, in its regulatory capacity, serves as the risk manager for contaminants in drinking water, while OEHHA is the risk assessor.

One contaminant for which DHS plans to adopt an MCL is chromium-6. (Chromium-6 is currently regulated as total chromium, a combination of chromium-3 and chromium-6.) Consistent with the provisions of the Statute, OEHHA will be developing a PHG for chromium-6, which may include an evaluation of the carcinogenic risk of the chemical.

Purpose of the Committee

The purpose of the Committee is to present written recommendations, and their scientific basis, to the Director of OEHHA, on the questions below regarding the potential carcinogenic risks of chromium-6 in drinking water, based on an evaluation of the scientific literature and exclusively on public health considerations as described in the introduction. OEHHA will consider these recommendations in developing a chromium-6 PHG.

The Evaluation Will Focus on the Following Questions:

1) Considering the toxicology, epidemiology and mechanistic information available regarding chromium-6, should chromium-6 be considered as posing a carcinogenic risk by the oral route?

2) If chromium-6 is to be considered as posing a carcinogenic risk by the oral route, what approaches does the Committee suggest to establish a PHG?

· The Borneff et al., (1968) mouse study is the only animal drinking water study of which we are aware that was designed to look at the potential carcinogenic effects of chromium-6. We are seeking your comments on the strengths and weaknesses of this study for purposes of making a quantitative estimate of the cancer risk for chromium-6 in humans.

· Does the epidemiology literature contain studies that would be useful to derive a cancer potency for chromium-6, such as, using the occupational data reporting excess gastrointestinal or other non-respiratory tumors?

· If the available literature does not allow the development of a cancer potency factor, what studies are available that would allow the development of a PHG that could take into account potential cancer risks from chromium-6. For example, some agencies apply an additional safety factor to the non-cancer chronic health effects observed in animals.

3) The conversion of chromium-6 to chromium-3 by simple chemical reactions in the stomach and pharmacokinetics after absorption can influence the toxic effects of chromium-6.

· How can the effects be quantified and the results applied as part of the approach in developing a PHG? As examples:

(1) Change the slope of the dose-response curve;

(2) Change the shape of the dose-response curve.

· Is there literature that indicates variability in the general population in the conversion of chromium-6 to chromium-3?

· Is there adequate information to identify a threshold for the oral route of exposure?