The distribution, sources and health risk of N-nitrosamines in karst dominated water of Liujiang River, Southwest China

Abstract

N-nitrosamines are a new class of disinfection byproducts with significant toxicity and carcinogenicity that have attracted extensive attention worldwide in recent years. N-nitrosamines in natural and drinking water would have adverse effects on people. The occurrence of N-nitrosamines in surface water, groundwater, and tap water of the Liujiang River Basin was investigated to disclose the source, fate, and cancer risk of N-nitrosamines in a typical karstic river. The origins of N-nitrosamines contamination were investigated using principal component analysis and multiple linear regression (PCA-MLRA). The results indicated that the concentrations of nine N-nitrosamines species were NDMA (1.7–342 ng/L), NMEA (ND, ND represents not detected), NPYR (2.5–53 ng/L), NDBA (ND-87 ng/L), NDEA (0.2–5.7 ng/L), NDPA (ND-34 ng/L), NPIP (ND-32 ng/L), NMOR (0.1–5.2 ng/L), and NDPhA (ND-0.3 ng/L). 71% of N-nitrosamines in the surface water samples of the Liujiang River's mainstream could be attributed to industrial and aquaculture effluents. Furthermore, 29% of N-nitrosamines could originate from domestic sewage and agricultural operations. In addition, we estimated the cancer risks associated with N-nitrosamines in groundwater and drinking water. For lifetime exposure (from birth to age 70), the average estimated carcinogenic risks of groundwater and tap water from oral intake were 7.4 × 10⁻⁵ (7.4 extra cancer cases per 100,000 persons exposed) and 9.7 × 10⁻⁵, respectively, which were greater than the US EPA standard (1 × 10⁻⁵). N-nitrosamines posed the highest cancer risk to children aged one to six. The experimental results would serve as a data foundation for environmental governance in typical karst regions.