Abstract: Localized/regional nasopharyngeal and hepatocellular carcinoma in South China are the typical cancer types by regional malignant tumor, ravaging public health in the area for hundreds of years. In this paper, taking the centuries old regional carcinoma epidemic in the Pearl River Delta as an example, applying epidemiology and ecogeochemical methodology, we determined that both environmental and drinking waters contained N-nitrosamine, a known carcinogen. We investigated the formation mechanism of N-nitrosamines compounds in natural waters under the constraints of regional geological, climate, hydrologic and ecological conditions. We developed a solid-phase extraction method (SPE) adaptable to gas chromatography-mass spectrometric (GC-MS) analysis to detect nine trace N-nitrosamine compounds in environmental and drinking waters. The detection limit ranged from 0.34 to 2.19 ng/L. In two representative cancer high-risk areas, Shunde and Sihui, we performed for the first time quantitive analysis of nine trace N-nitrosamines in different water occurrences. The results showed that the N-nitrosamine concentrations in local waters ranged from 0.34 to 307 ng/L. And the detection rate of 40% was much higher than the 15% rate set by healthy drinking water standard for N-nitrosamines at 10 ng/L. The testing results indicated NDMA and NDBA were the main pollutants, while other nitrosamines were detected at lower concentrations. In the less industrialized Sihui area, nitrosamine concentrations share the same statistical characteristics for different water occurrences such as well, tap, underground and spring waters: the average and peak values of NDMA and NDBA barely exceeded the standards at 21.77 and 15.54 ng/L, respectively, higher than other nitrosamines. This was a typical nitrosamine composition profile for the natural regional underground water. The water samples were taken from wells at 020 m depths. The underground water is ammonium-rich and contains nitrosamines formed under unique regional ecogeological and climate conditions, and it may be the original culprit of the regional carcinoma. Among the five endemic regions studied, the industrialized Shunde area has highest nitrosamine content, with nitrosamine concentration correlating positively with hepatocellular carcinoma morbidity. Our study confirmed that cumulative effect of industrial pollution can increase cancer morbidity.

Key words: regional cancer, GC/El-MS/MS analytic method for nitrosamines, detecting trace nitrosaminesin drinking water, underground water containing nitrosamines, cumulate pollution, nitrogen-rich eutrophication in soil and water, Pearl River Delta region