Department of Public Health, Aarhus University, Aarhus, Denmark.
Department of Groundwater and Quaternary Geology Mapping, Geological Survey of Denmark and Greenland, Aarhus, Denmark.
Int J Cancer. 2018 Jul 1;143(1):73-79. doi: 10.1002/ijc.31306. Epub 2018 Feb 23.
Nitrate in drinking water may increase risk of colorectal cancer due to endogenous transformation into carcinogenic N-nitroso compounds. Epidemiological studies are few and often challenged by their limited ability of estimating long-term exposure on a detailed individual level. We exploited population-based health register data, linked in time and space with longitudinal drinking water quality data, on an individual level to study the association between long-term drinking water nitrate exposure and colorectal cancer (CRC) risk. Individual nitrate exposure was calculated for 2.7 million adults based on drinking water quality analyses at public waterworks and private wells between 1978 and 2011. For the main analyses, 1.7 million individuals with highest exposure assessment quality were included. Follow-up started at age 35. We identified 5,944 incident CRC cases during 23 million person-years at risk. We used Cox proportional hazards models to estimate hazard ratios (HRs) of nitrate exposure on the risk of CRC, colon and rectal cancer. Persons exposed to the highest level of drinking water nitrate had an HR of 1.16 (95% CI: 1.08-1.25) for CRC compared with persons exposed to the lowest level. We found statistically significant increased risks at drinking water levels above 3.87 mg/L, well below the current drinking water standard of 50 mg/L. Our results add to the existing evidence suggesting increased CRC risk at drinking water nitrate concentrations below the current drinking water standard. A discussion on the adequacy of the drinking water standard in regards to chronic effects is warranted.
饮用水中的硝酸盐可能会因内源性转化为致癌的 N-亚硝基化合物而增加结直肠癌的风险。此类流行病学研究较少，并且由于其在详细个体水平上估计长期暴露的能力有限而经常受到挑战。我们利用基于人群的健康登记数据，在个体水平上，在时间和空间上与纵向饮用水质量数据进行了关联，以研究长期饮用水硝酸盐暴露与结直肠癌（CRC）风险之间的关系。根据 1978 年至 2011 年公共供水厂和私人水井的饮用水质量分析，为 270 万成年人计算了个体硝酸盐暴露量。在主要分析中，纳入了最高暴露评估质量的 170 万人。随访从 35 岁开始。我们在 2.3 亿人年的风险期内确定了 5944 例结直肠癌新发病例。我们使用 Cox 比例风险模型来估计硝酸盐暴露对 CRC、结肠癌和直肠癌风险的危害比（HR）。与暴露于最低水平的人相比，暴露于最高水平饮用水硝酸盐的人患 CRC 的 HR 为 1.16（95%CI：1.08-1.25）。我们发现，在饮用水水平高于 3.87mg/L 时，风险呈统计学显著增加，远低于当前 50mg/L 的饮用水标准。我们的研究结果为现有证据增添了内容，表明在低于当前饮用水标准的饮用水硝酸盐浓度下，结直肠癌风险增加。需要就慢性影响的饮用水标准是否充分进行讨论。
