Proceedings

Disinfection by-products (DBPs) are chemical compounds with adverse human health effects (e.g.
carcinogenicity) that are formed during drinking water treatment from the reaction of chemical
disinfectants (e.g. chlorine) with natural organic matter. In the UK, trihalomethanes (THMs) are the only
class of regulated DBPs currently, with a limit of 100 µg/L in tap water. However, there are many other
DBPs that may form during water treatment and distribution. N-nitrosodimethylamine (NDMA) is a potent
carcinogen (much more potent than THMs) that has recently been proven to be a drinking water DBP that
is formed under certain circumstances. There is currently a limited understanding of the spatial and
temporal trends of the concentrations of NDMA and other nitrosamine compounds in treatment works
and distribution networks. This study reports the early findings of an ongoing survey of NDMA and seven
other nitrosamines from six drinking water supply systems in England and Scotland that were identified as
being probable to have elevated concentrations of these compounds.

Key Words
Disinfection, disinfection by-products, drinking water treatment, NDMA, nitrosamines