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DBCP In Drinking Water: What Does It Mean? Page 5 DBCP at 0.2 ppb for 70 years, one of them might contact cancer from drinking the water. This should be kept in perspective with the natural background rate of cancer, which is 1 case in every 4 people over a lifetime. Thus in a population of 10,000 an estimated 2,500 people would get cancer anyway, and the total number of cases would only be increased to 2,501 by DBCP. The number of theoretical additional cancer caused due to DBCP in drinking water has been applied to the exposed population in California and the following benefits have been calculated from the new MCL: • Reduces the excess theoretical cancer cases from DBCP lifetime exposure from 163 to 6 in California. Reduces by 185,000 the number of California exposed to excessive levels of DBCP in drinking water from public water systems. This will be achieved by requiring that the 184 public wells contaminated with DBCP over 0.2 ppb be removed from services or the water be treated to meet MCL. • Protects against the potential infertility hazard for all affected Californians. It is important to note that risk assessments are likely to estimate a higher number of cancer cases than would actually occur. For example a standard 70 -year lifetime is used for the length of exposure in these calculations. The actual exposure for the population is considerably shorter if people move around or don't drink all their water at home. The costs of implementing the MCL have been estimated as follows: One time capitol cost of $28.6 million. Yearly operating and maintenance costs for treatment estimated at 4.3 million for the first five years, and 2.2 to 2.7 million for years 2-5. A yearly average per capita to the consuming public ranging from $0.08 to $269.77. The cost of trying to reduce the number of theoretical excess cancer cases below the level provided by 0.2 ppb was found to outweigh the benefits. HOW CAN DBCP BE REMOVED FROM DRINKING WATER? DBCP is highly mobile and long lasting in ground water. Its half-life in ground water has been estimated to range from 3.1 to 400 years depending on water temperature and pH. The median half-life value is 20 years. (Half-life refers to the time it takes for the