Brown K G, Chen C J
Institute of Public Health, National Taiwan University, Taipei, Republic of China.
Risk Anal. 1995 Aug;15(4):475-84. doi: 10.1111/j.1539-6924.1995.tb00340.x.
The primary source of evidence that inorganic arsenic in drinking water is associated with increased mortality from cancer at internal sites (bladder, liver, lung, and other organs) is a large ecologic study conducted in regions of Southwest Taiwan endemic to Blackfoot disease. The dose-response patterns for lung, liver, and bladder cancers display a nonlinear dose-response relationship with arsenic exposure. The data do not appear suitable, however, for the more refined task of dose-response assessment, particularly for inference of risk at the low arsenic concentrations found in some U.S. water supplies. The problem lies in variable arsenic concentrations between the wells within a village, largely due to a mix of shallow wells and deep artesian wells, and in having only one well test for 24 (40%) of the 60 villages. The current analysis identifies 14 villages where the exposure appears most questionable, based on criteria described in the text. The exposure values were then changed for seven of the villages, from the median well test being used as a default to some other point in the village's range of well tests that would contribute to smoothing the appearance of a dose-response curve. The remaining seven villages, six of which had only one well test, were deleted as outliers. The resultant dose-response patterns showed no evidence of excess risk below arsenic concentrations of 0.1 mg/l. Of course, that outcome is dependent on manipulation of the data, as described. Inclusion of the seven deleted villages would make estimates of risk much higher at low doses. In those seven villages, the cancer mortality rates are significantly high for their exposure levels, suggesting that their exposure values may be too low or that other etiological factors need to be taken into account.
饮用水中的无机砷与体内部位（膀胱、肝脏、肺和其他器官）癌症死亡率增加相关的主要证据来源是在台湾西南部黑脚病流行地区进行的一项大型生态学研究。肺癌、肝癌和膀胱癌的剂量反应模式显示出与砷暴露呈非线性剂量反应关系。然而，这些数据似乎不适用于更精细的剂量反应评估任务，特别是对于推断美国一些供水系统中发现的低砷浓度下的风险。问题在于村庄内各水井之间的砷浓度存在差异，这主要是由于浅井和深自流井混合造成的，而且60个村庄中有24个（40%）村庄仅进行了一次水井检测。根据文中所述标准，当前分析确定了14个暴露情况最值得怀疑的村庄。然后，对其中7个村庄的暴露值进行了更改，从将水井检测中位数用作默认值改为村庄水井检测范围内有助于使剂量反应曲线外观更平滑的其他某个点。其余7个村庄（其中6个村庄仅进行了一次水井检测）作为异常值被删除。最终的剂量反应模式显示，在砷浓度低于0.1毫克/升时没有超量风险的证据。当然，如所述，该结果依赖于对数据的处理。纳入这7个被删除的村庄会使低剂量风险估计值高得多。在这7个村庄中，按其暴露水平来看癌症死亡率显著较高，这表明它们的暴露值可能过低，或者需要考虑其他病因因素。
