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Pools for Emergency Drinking Water Page 2 higher in small pools than in larger ones. Our conclusions may not apply to spas, jacuzzis, or hot tubs, which often require different chemicals than do pools, and which can have a heavier bather load, making water quality more difficult to predict. MET$01?S. ` We first assessed the health risks that might theoretically be associated with ingesting expected concentrations of various contaminants in pool water, focusing on minerals and trace metals normally tested for in drinking water and on chemicals commonly added to swimming pools. In conducting this risk assessment, we relied on a number of assumptions described below. We then tools water samples from 50 reasonably well maintained pools, for standard drinking water analyses. Kicks fxaChe.micai Counts -- Assamp1ions Mado With regard to chemical contaminants, we have made some simple estimates of how large a dose of each chemical one might get from using pool water for drinking, under plausibly conservative assumptions. These �• assumptions are as follows: 1) To the pool water has been added the maximal amount of chemical which might reasonably be used in the course of competent maintenance of the pool. 2) The pool contains 12,500 gallons (50,000 liters). This a small pool. This assumption will probably lead to a conservative (health protective) assessment of risk, since for certain contaminants small pools would be predicted to have greater concentrations than would larger pools. 3) An adult drinks 2 liters of water a day from the pool; a 10-kg child drinks 1 liter of water a day from the pool_ Subjects will drink this water for 14 days. 4) The pool has not been drained for five years. (Some private pools may be drained no more often than every ten years; for these, the conclusions below may not apply if large amounts of copper have been used in the pool.) Some substances, such as metal ions, will accumulate; we have made no provision for splash-out but instead assume that all metals added to the water remain for the entire life of that pool water. Other chemicals probably accumulate only partially; for these we have tried to pick accumulation times that are plausibly conservative. 5) We have assumed no toxicologic interactions among these chemicals. Although we do not have very good information in general for multiple chemical interactions, we do not see any significant interactions for these particular chemicals over this relatively short length of time. For estimating health risks from chemical contaminants, we have relied heavily on toxicity estimates contained in a series of monographs on Drinking Water and Health published by the National Research Council.