Occurrence of nitrosamines and their precursors in North American drinking waters.

Heads up: Nitrosamines, which are really strong cancer-causing compounds from water disinfection, have popped up in treated drinking water all over North America. How much you find depends a lot on the disinfection method and the quality of the source water. N-nitrosodimethylamine (NDMA) is the most common one we see. It mostly forms when chloramine-based disinfection reacts with certain compounds already in the source water.

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Source: Water Feed

Frequently Asked Questions

What are nitrosamines and why are they a concern in North American drinking water?

Nitrosamines are a class of potent carcinogenic disinfection byproducts (DBPs) detected in treated drinking waters across North America. While not currently regulated by the U.S. EPA, they are significantly more carcinogenic on a per-mass basis than regulated DBPs like trihalomethanes (THMs). Their presence raises significant public health concerns due to potential long-term health impacts.

How does N-nitrosodimethylamine (NDMA) primarily form in drinking water?

N-nitrosodimethylamine (NDMA), the most commonly detected nitrosamine, primarily forms when chloramine-based disinfection reacts with specific precursor compounds in source water. Studies indicate that factors like elevated ammonia and precursors during spring runoff, or the use of poly(diallyldimethylammonium chloride) (polyDADMAC), can increase its formation.

Are nitrosamines currently regulated in North American drinking water supplies?

Nitrosamines are not currently regulated under the U.S. EPA Stage 1 or Stage 2 Disinfectants and Disinfection Byproducts Rules. However, the California Department of Public Health (CDPH) has established a notification level of 10 ng/L for NDMA, and Health Canada has proposed similar guidelines, reflecting growing concern over these compounds.

Which disinfection methods are associated with higher NDMA levels in drinking water?

Chloramine-based disinfection systems are preferentially associated with higher NDMA formation, with studies showing median levels of 4.4 ng/L. In contrast, chlorinated systems typically produce less NDMA, often below 2.0 ng/L. Temporarily switching from chloramines to chlorine has been observed to significantly reduce NDMA formation.

What factors contribute to increased NDMA formation in source water?

Increased NDMA formation is often linked to specific source water conditions and treatment practices. Higher levels of ammonia and NDMA precursors in source water, particularly during spring runoff, contribute to greater formation. Additionally, the use of poly(diallyldimethylammonium chloride) (polyDADMAC) has been correlated with increased NDMA production.