| Development of a Health-Protective Drinking Water Level for Perchlorate David Ting, Robert A. Howd, Anna M. Fan, and George V. Alexeeff Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California, USA Abstract
We evaluated animal and human toxicity data for perchlorate and identified reduction of thyroidal iodide uptake as the critical end point in the development of a health-protective drinking water level [also known as the public health goal (PHG) ] for the chemical. This work was performed under the drinking water program of the Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency. For dose-response characterization, we applied benchmark-dose modeling to human data and determined a point of departure (the 95% lower confidence limit for 5% inhibition of iodide uptake) of 0.0037 mg/kg/day. A PHG of 6 ppb was calculated by using an uncertainty factor of 10, a relative source contribution of 60%, and exposure assumptions specific to pregnant women. The California Department of Health Services will use the PHG, together with other considerations such as economic impact and engineering feasibility, to develop a California maximum contaminant level for perchlorate. We consider the PHG to be adequately protective of sensitive subpopulations, including pregnant women, their fetuses, infants, and people with hypothyroidism. Key words: drinking water level, human health, iodine intake, NIS, perchlorate, risk assessment, sensitive subpopulation, thyroid hormone. Environ Health Perspect 114: 881-886 (2006) . doi:10.1289/ehp.8684 available via http://dx.doi.org/ [Online 26 January 2006]
Address correspondence to D. Ting, Pesticide and Environmental Toxicology Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, 1515 Clay St., 16th Floor, Oakland, CA 94612 USA. Telephone: (510) 622-3226. Fax: (510) 622-3218. E-mail: dting@oehha.ca.gov We thank the University of California and the U.S. EPA for their critical review comments. We are also grateful for the inputs and suggestions provided by interested parties and the general public. This work was carried out under the drinking water program of the Office of Environmental Health Hazard Assessment, California Environmental Protection Agency. The authors declare they have no competing financial interests. Received 26 September 2005 ; accepted 26 January 2006. The full version of this article is available for free in HTML or PDF formats. |
