DRINKING WATER STANDARD FOR TRITIUM—WHATʼS THE RISK?

• Published in: Health physics (1958) Vol. 101; no. 3; pp. 274 - 285
• Main Authors: Kocher, D. C, Hoffman, F. O
• Format: Journal Article
• Language: English
• Published: United States Health Physics Society 01-09-2011; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Adolescent; Child, Preschool; Correlation analysis; Drinking; Drinking water; Female; Humans; Infant; Male; Maximum Allowable Concentration; Neoplasms - chemically induced; Neoplasms - mortality; Neoplasms - pathology; Probability distribution; Risk assessment; Risk Assessment - methods; Risk Assessment - statistics & numerical data; Skin cancer; Skin Neoplasms - chemically induced; Skin Neoplasms - mortality; Skin Neoplasms - pathology; Tritium - analysis; Tritium - standards; Tritium - toxicity; United States; United States Environmental Protection Agency; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - standards; Water Pollutants, Chemical - toxicity; Water Supply - analysis; Water Supply - standards; United States; USA
• ISSN: 0017-9078; 1538-5159
• DOI: 10.1097/HP.0b013e31820ff161

This paper presents an assessment of lifetime risks of cancer incidence associated with the drinking water standard for tritium established by the U.S. Environmental Protection Agency (USEPA); this standard is an annual-average maximum contaminant level (MCL) of 740 Bq L. This risk assessment has several defining characteristics(1) an accounting of uncertainty in all parameters that relate a given concentration of tritium in drinking water to lifetime risk (except the number of days of consumption of drinking water in a year and the number of years of consumption) and an accounting of correlations of uncertain parameters to obtain probability distributions that represent uncertainty in estimated lifetime risks of cancer incidence; (2) inclusion of a radiation effectiveness factor (REF) to represent an increased biological effectiveness of low-energy electrons emitted in decay of tritium compared with high-energy photons; (3) use of recent estimates of risks of cancer incidence from exposure to high-energy photons, including the dependence of risks on an individualʼs gender and age, in the BEIR VII report; and (4) inclusion of risks of incidence of skin cancer, principally basal cell carcinoma. By assuming ingestion of tritium in drinking water at the MCL over an average life expectancy of 80 y in females and 75 y in males, 95% credibility intervals of lifetime risks of cancer incidence obtained in this assessment are (0.35, 12) × 10 in females and (0.30, 15) × 10 in males. Mean risks, which are considered to provide the best single measure of expected risks, are about 3 × 10 in both genders. In comparison, USEPAʼs point estimate of the lifetime risk of cancer incidence, assuming a daily consumption of drinking water of 2 L over an average life expectancy of 75.2 y and excluding an REF for tritium and incidence of skin cancer, is 5.6 × 10. Probability distributions of annual equivalent doses to the whole body associated with the drinking water standard for tritium also were obtained. Means and 97.5 percentiles of maximum annual doses to females and males, which occur at age <1 y, all are less than the annual equivalent dose of 40 μSv used by USEPA to establish the MCL.