Background
Nitrosamines (NAms) are highly carcinogenic and frequently detected in drinking water systems in China, indicating potential human health risk through drinking water.
Objective
To analyze the distribution of NAms in drinking water in Shanghai and to evaluate relevant human health risk.
Methods
A total of 94 samples of source water and 120 samples of finished water were collected in February (dry period) and August (wet period) of 2021 from 30 drinking water plants in Shanghai, and eight NAms were quantitatively analyzed by gas chromatography tandem mass spectrometry after solid phase extraction. Cancer risks for different age groups caused by NAms exposure through water were evaluated using Monte Carlo probabilistic method and carcinogens risk assessment model recommended by the United States Environmental Protection Agency.
Results
The concentrations of total NAms in source and finished water were 12.56-65.86 ng·L−1 and 8.52-57.38 ng·L−1, respectively. The average concentration of total NAms was higher in source water (33.50 ng·L−1) than in finished water (22.07 ng·L−1, P<0.05) during dry season, and lower in source water (16.90 ng·L−1) than in finished water (21.02 ng·L−1, P<0.05) during wet season. The average concentration of total NAms in source water during dry season was twice of that during wet season. The positive rate of N-nitrosodimethylamine (NDMA) was the highest (100%) among the eight NAms. The cancer risk of exposure to NAms in finished water in Shanghai was mainly from the ingestion route, which was mostly caused by NDMA. The cancer risk from exposure to NAms in water for children (median=4.32×10−5) was slightly higher than that for adults (median=3.34×10−5) and adolescents (median=2.27×10−5). The cancer risks of exposure to NAms in water for people of different ages were mainly (80% - 95%) at an acceptable level (1×10−6 - 1×10−4).
Conclusion
NAms contamination is positive in Shanghai’s drinking water and NDMA is the main contaminant. The removal of NAms in water by current water treatment process is season-dependent. The cancer risk of children exposed to NAms in water was slightly higher than that of adults and adolescents, but all at acceptable levels.
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