ABSTRACT

Nitrate, as a major pollutant of drinking water, is associated with colorectal cancer (CRC) and serves as an environmental health concern, especially in the districts with unregulated agriculture. In this case study in northwestern Iran, we used two databases of nitrate concentration (1999–2013) and age-standardized incidence rate (ASR) for CRC (2002–2012) from 19 counties of East Azerbaijan province. The trend and correlation between nitrate and ASR was investigated. Inverse distance weighted technique was used to spatially interpolate the maps. Expectedly, drinking water nitrate has increased throughout the province (8–20.5 mg/L) as well as the ASR for CRC of men (from 2.07 to 18.05 mg/L) and women (from 1.57 to 10.94 mg/L). While ASR for CRC of men was positively correlated to nitrate (Pearson’s r = 0.624, p-value = 0.040), no statistically significant correlation was found between nitrate and ASR for women’s CRC (Pearson’s r = 0.289, p-value = 0.351). According to our findings, the incidence of CRC was not higher for those residing in the regions with higher nitrate, suggesting that risk factors such as genetic predisposition and diet that were not taken into account could be determinants of this pattern. However, even a small increase in CRC rate due to water nitrate could translate into a large public health concern. The incremental pattern observed in nitrate levels of different counties over the years gives the health policymakers a better perspective of the problem and how the control of water nitrate level as a CRC risk factor might contribute to the prevention of CRC.

摘要

硝酸盐作为饮用水的主要污染物，与结直肠癌 (CRC) 相关，并引起环境健康问题，尤其是在农业不受管制的地区。在伊朗西北部的这个案例研究中，我们使用了来自东阿塞拜疆省 19 个县的 CRC（2002-2012 年）硝酸盐浓度（1999-2013 年）和年龄标准化发病率（ASR）的两个数据库。研究了硝酸盐和ASR之间的趋势和相关性。使用反距离加权技术对地图进行空间插值。预计，全省饮用水硝酸盐增加（8-20.5 mg/L）以及男性（从 2.07 到 18.05 mg/L）和女性（从 1.57 到 10.94 mg/L）的 ASR。虽然男性 CRC 的 ASR 与硝酸盐呈正相关（Pearson 的r = 0.624，p值 = 0.040），在女性 CRC 的硝酸盐和 ASR 之间没有发现统计学上的显着相关性（Pearson 的r = 0.289，p-值 = 0.351）。根据我们的研究结果，居住在硝酸盐含量较高地区的人的 CRC 发病率并不高，这表明未考虑的遗传易感性和饮食等风险因素可能是这种模式的决定因素。然而，即使是由于硝酸盐而导致的 CRC 发病率的小幅增加也可能转化为重大的公共卫生问题。多年来在不同县的硝酸盐水平观察到的增量模式使卫生政策制定者更好地了解这个问题，以及控制作为 CRC 风险因素的水硝酸盐水平如何有助于预防 CRC。