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The identification and measurement of drinking water disinfection byproducts (DBPs) hasfocused on compounds that contain halogen. Review of epidemiological and toxicological datathat are currently available suggests that adverse health effects associated with chlorination ofdrinking water cannot be accounted for by the commonly measured DBPs within the THM andHAA classes. These compounds fail to account for the health effects associated with chlorinatedwater 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 consistentlyassociated with chlorinated water, cancer of the urinary bladder. Although some members ofthese 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 beemerging from epidemiological studies. This suggests that a more productive method oforganizing a research effort to solve this problem would be to seek to identify DBPs that havethe potential of possessing both the target organ specificity and potency to account forepidemiological findings. The identification of N-dimethyl-N-nitrosamine (NDMA) in somedrinking waters is the first demonstration of a DBP that may at least occasionally be produced inquantities sufficient to carry the levels of risk implied by epidemiological findings. NDMA isprimarily a liver carcinogen, and therefore fails the criteria of specificity. However, other nitrosamines andnitrosoureas have been identified as bladder carcinogens. Analytical methods for more robustmeasurement 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-containingorganic classes. Some, but not all of these chemicals are potent carcinogens. It does not seemnecessary to invoke nitrogen-containing organic chemicals to account for reproductive anddevelopmental effects. Byproducts in the haloacetic acid class and chlorate have appropriatespecificity for such effects. However, their potencies are much too low. This lack of appropriatepotency may be most simply satisfied by determining the occurrence and toxicological propertiesof related higher chain halogenated organic acids and aldehydes. These examples illustrate howthe research focus in the DBP area could be more efficiently structured to deal withepidemiological associations with adverse health impacts related to drinking water treatment. Includes 18 references, tables.

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Edition: Vol. - No. Published: 06/15/2003 Number of Pages: 11File Size: 1 file , 260 KB