Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan.
J Toxicol Environ Health A. 2010;73(19):1337-47. doi: 10.1080/15287394.2010.490178.
The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and increased risk of death from rectal cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of nitrate on development of rectal cancer. A matched case-control study was used to investigate the relationship between the risk of death from rectal cancer and exposure to nitrate in drinking water in Taiwan. All rectal cancer deaths of Taiwan residents from 2003 through 2007 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO(3)-N), Ca, and Mg in drinking water was collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO(3)-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO(3)-N exposure level was <0.38 ppm, the adjusted odds ratio (OR) (95% CI) for rectal cancer occurrence was 1.15 (1.01-1.32) for individuals who resided in municipalities served by drinking water with a NO(3)-N exposure > or =0.38 ppm. There was no apparent evidence of an interaction between drinking water NO(3)-N levels with low Mg intake via drinking water. However, evidence of a significant interaction was noted between drinking-water NO(3)-N concentrations and Ca intake via drinking water. Our findings showed that the correlation between NO(3)-N exposure and risk of rectal cancer development was influenced by Ca in drinking water. This is the first study to report effect modification by Ca intake from drinking water on the association between NO(3)-N exposure and risk of rectal cancer occurrence. Increased knowledge of the mechanistic interaction between Ca and NO(3)-N in reducing rectal cancer risk will aid in public policymaking and setting threshold standards.
(1) 检验公共供水中硝酸盐水平与直肠癌死亡风险增加之间的关系；(2) 确定饮用水中钙 (Ca) 和镁 (Mg) 水平是否可能改变硝酸盐对直肠癌发展的影响。采用病例对照研究方法，调查台湾地区居民饮用水中硝酸盐暴露与直肠癌死亡风险之间的关系。所有 2003 年至 2007 年台湾地区居民直肠癌死亡病例均来自台湾省卫生厅生命统计处。对照病例为其他死因，并按性别、出生年份和死亡年份与病例相匹配。从台湾自来水公司 (TWSC) 收集饮用水中硝酸盐氮 (NO3-N)、Ca 和 Mg 水平的信息。根据癌症病例和对照的居住地，假设市政供水是其通过饮用水暴露于 NO3-N、Ca 和 Mg 的来源。与 NO3-N 暴露水平<0.38ppm 的个体相比，NO3-N 暴露水平≥0.38ppm 的市政供水地区居民患直肠癌的调整比值比 (OR) (95% CI) 为 1.15(1.01-1.32)。饮用水 NO3-N 水平与低 Mg 摄入之间没有明显的交互作用。然而，在饮用水 NO3-N 浓度与饮用水 Ca 摄入之间发现了显著的交互作用。我们的研究结果表明，NO3-N 暴露与直肠癌发展风险之间的相关性受到饮用水中 Ca 的影响。这是第一项报告饮用水 Ca 摄入量对 NO3-N 暴露与直肠癌发生风险之间关联的修饰作用的研究。增加对 Ca 与 NO3-N 之间在降低直肠癌风险方面的相互作用机制的认识，将有助于公共政策制定和设定阈值标准。
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