AWWA ACE58256

The identification and measurement of drinking water disinfection byproducts (DBPs) has focused on compounds that contain halogen. Review of epidemiological and toxicological data that are currently available suggests that adverse health effects associated with chlorination of drinking water cannot be accounted for by the commonly measured DBPs within the THM and HAA classes. These compounds fail to account for the health effects associated with chlorinated water in epidemiological studies by two criteria, one of specificity and the other of potency. First, none of these byproducts has been shown to produce the cancer most consistently associated with chlorinated water, cancer of the urinary bladder. Although some members of these classes can cause other types of cancer, reproductive effects, and developmental effects, their potency is orders of magnitude too low to account for other associations that seem to be emerging from epidemiological studies. This suggests that a more productive method of organizing a research effort to solve this problem would be to seek to identify DBPs that have the potential of possessing both the target organ specificity and potency to account for epidemiological findings. The identification of N-dimethyl-N-nitrosamine (NDMA) in some drinking waters is the first demonstration of a DBP that may at least occasionally be produced in quantities sufficient to carry the levels of risk implied by epidemiological findings. NDMA is primarily a liver carcinogen, and therefore fails the criteria of specificity. However, other nitrosamines and nitrosoureas have been identified as bladder carcinogens. Analytical methods for more robust measurement of nitroso compounds in drinking water will be needed to evaluate this hypothesis. Chemicals that are known to target the urinary bladder come largely from nitrogen-containing organic classes. Some, but not all of these chemicals are potent carcinogens. It does not seem necessary to invoke nitrogen-containing organic chemicals to account for reproductive and developmental effects. Byproducts in the haloacetic acid class and chlorate have appropriate specificity for such effects. However, their potencies are much too low. This lack of appropriate potency may be most simply satisfied by determining the occurrence and toxicological properties of related higher chain halogenated organic acids and aldehydes. These examples illustrate how the research focus in the DBP area could be more efficiently structured to deal with epidemiological associations with adverse health impacts related to drinking water treatment. Includes 18 references, tables.