There are a number of regulatory and policy approaches regarding the issue of pollutants, which occur in wide ranges of contaminant concentrations, and ingestion habits. Mean values for NDMA used to calculate mean daily intakes based on average consumption values are somewhat meaningless when applied to individuals within a population. This is particularly true for NDMA, for which ingestion of the main dietary sources (cured meats and beer) varies from nil to multiples of the average amounts, depending on personal habits. Furthermore, looking at the relative contributions of NDMA from different sources is only marginally meaningful. It is the absolute amounts that are consumed that need to be addressed, and looking at ways to ensure that these are minimized and water plays an increasing role in those.
Given that NDMA can form during water and wastewater treatment, and that in some severe cases drinking water may provide as much or more dietary NDMA as food, some degree of formal monitoring of NDMA in drinking water must be required, particularly when disinfection techniques promoting formation are practiced.
Currently, NDMA in drinking water is regulated in very few countries worldwide, although it is now limited to 9 and 10 ng/L by the state and provincial governments in California and Ontario, respectively. These values exceed the 0.7ng/L drinking water concentration suggested by the U.S. Environmental Protection Agency (EPA) to result in a 10~6 lifetime cancer risk . Further, the World Health Organization is considering a guideline value of 100ng/L to be included in the second addendum to the 3rd edition of the World Health Organization (WHO) Guidelines for Drinking Water Quality . This is in agreement with German regulations for carcinogenic substances that have some level of uncertainty associated with their evaluation, which in the case of NDMA resulted at 100ng/L . There is presently no standard in the United Kingdom or the European Union. Since NDMA is likely a human carcinogen, its presence as a contaminant in drinking water is of concern, and consideration should be given to its wider regulation as well as the feasibility of monitoring and treatment options to prevent the occurrence of NDMA in water supplies.
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