Estimation of the Total Daily Oral Intake of N-Nitrosodimethylamine (NDMA) Attributable to the Consumption of Drinking Water

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TAB4-PD-03 Disinfection with chlorine and chloramine leads to the formation of many disinfection by-products (DBPs) including nitrogenous DBPs, such as N-nitrosodimethylamine (NDMA). Because NDMA is a probable human carcinogen, public health officials are concerned with its occurrence in drinking water. The goal of this study was to estimate NDMA concentrations in drinking water and foods, calculate the average daily dose (ADD) for ingestion route exposures, and estimate the relative contribution of NDMA in drinking water to that of the exogenous NDMA present in foods and from endogenous synthesis in the human body. The proportional oral intake (POI) attributable to the consumption of drinking water is predicted to be 0.1% and 1.5% for exogenous and endogenous sources combined and only exogenous sources, respectively. Although NDMA concentrations in foods are typically low, human exposure to NDMA through the consumption foods is predicted to be high relative to that of drinking water. To put the ADD estimates further into perspective, the exposure model suggests that the mean NDMA concentration in drinking water would need to increase from 2.3 ×10−3 μg/L to 0.12 μg/L, a 50-fold increase, for the POI to reach 1%.