Physical Injury Risks Associated with Drinking Water Arsenic Treatment Floyd J. Frost, 1 * Joseph Chwirka, 2 Gunther F. Craun, 3 Bruce Thomson, 4 and John Stomp 5 We estimated the number of transportation deaths that would be associated with water treatment in Albuquerque to meet the EPA’s recently proposed revisions of the Maximum Contaminant Level (MCL) for arsenic. Vehicle mileage was estimated for ion exchange, activated alumina, and iron coagulation/microfiltration water treatment processes to meet an MCL of 0.020 mg/L, 0.010 mg/L, 0.005 mg/L, and 0.003 mg/L. Local crash, injury, and death rates per million vehicle miles were used to estimate the number of injuries and deaths. Depending on the water treatment options chosen, we estimate that meeting an arsenic MCL of 0.005 mg/L will result in 143 to 237 crashes, 58 to 98 injuries, and 0.6 to 2.6 deaths in Albuquerque over a 70-year period, resulting in 26 to 113 years of life lost. The anticipated health benefits for Albuquerque residents from a 0.005 mg/L arsenic MCL, estimated using either a multistage Weibull or Poisson model, ranged from 3 to 80 arsenic-related bladder and lung cancer deaths prevented over a 70-year period, adding between 43 and 1,123 years of life. Whether a revised arsenic MCL increases or reduces overall loss of life in Albuquerque depends on the accuracy of EPA’s cancer risk assessment. If the multistage Weibull model accurately estimates the benefits, the years of life added is comparable or lower than the anticipated years lost due to transportation associated with the delivery of chemicals, disposal of treatment waste, and operation of the water treatment system. Coagulation/microfiltration treatment will result in substantially fewer transportation deaths than either ion exchange or activated alumina. KEY WORDS: Arsenic health effects; transportation injury risks; drinking water treatment; maximum contaminant level; environmental cancer risks 1. INTRODUCTION The U.S. Environmental Protection Agency (EPA) has recently proposed a revised Maximum Contaminant Level (MCL) for arsenic, reducing the MCL from 0.050 to a level of 0.003 to 0.020 milligrams per liter (mg/L). (1) The EPA estimates that removing arsenic from drinking water will prevent the occurrence of and death from arsenic- related bladder and lung cancers and possibly other internal cancers and cardiovascular and hyperten- sive diseases. (1) The EPA (1) and others (2,3) have estimated that the arsenic-related lifetime risk of cancer death may be as high as one death per 100 people exposed to 0.050 mg/L from a risk assessment using data from an ecological study of a Taiwanese population of farmers and fishermen. Epidemiolog- ical studies of U.S. and European populations have not found comparable risks. (4–7) 1 Lovelace Clinic Foundation, Albuquerque, NM. 2 CH2M Hill, Albuquerque, NM. 3 Gunther F. Craun and Associates, Staunton, VA. 4 University of New Mexico, Albuquerque, NM. 5 Public Works Department, City of Albuquerque, Albuquerque, NM. *Address correspondence to Floyd Frost, Lovelace Clinic Foun- dation, 2425 Ridgecrest Dr. SE, Albuquerque, NM 87108; tel: 505-262-3471; fax: 505-262-7835; ffrost@lrri.org. Risk Analysis, Vol. 22, No. 2, 2002 235 0272-4332/02/0400-0235$22.00/1 Ó 2002 Society for Risk Analysis