Cech I, Holguin A H, Littell A S, Henry J P, O'Connell J
Int J Epidemiol. 1987 Jun;16(2):198-207. doi: 10.1093/ije/16.2.198.
In 1954, following the construction of Lake Houston, a change from lightly chlorinated ground sources to a heavily chlorinated surface source of drinking water took place for a sizable part of the population in the city of Houston, Texas. This has provided the opportunity to compare the incidence of urinary tract cancer mortality in populations exposed to heavily chlorinated and lightly chlorinated drinking water. The spatial, diurnal, and seasonal concentrations of chlorination byproducts (trihalomethanes) in Houston water were assessed. The range of concentrations varied from below the limits of detection in treated ground water, to more than 200 mg/l (twice the level allowed by US drinking water standards) in treated lake water. The mortality experience by gender, by race, and by age cohorts for the period 1940 to 1970 from urinary tract cancers and three comparison causes was determined for 56 of Houston's census tracts classified by the duration of exposure to the surface water. By the 1970's 20 years following the switch to surface water, an increase was detected in urinary cancer mortality rates for white females without a corresponding increase observed for white males. No clear-cut trends were found for the non-white population. On balance, a detrimental urinary cancer effect associated with a switch to chlorinated surface water has not been demonstrated yet.
1954年，在休斯顿湖建成后，得克萨斯州休斯顿市相当一部分人口的饮用水源从轻度氯化的地下水转变为深度氯化的地表水。这为比较接触深度氯化和轻度氯化饮用水的人群中尿路癌死亡率提供了机会。对休斯顿市水中氯化副产物（三卤甲烷）的空间、昼夜和季节浓度进行了评估。浓度范围从处理后的地下水中低于检测限，到处理后的湖水中超过200毫克/升（是美国饮用水标准允许水平的两倍）。根据接触地表水的持续时间，对休斯顿56个人口普查区1940年至1970年期间按性别、种族和年龄组划分的尿路癌及三种对照病因的死亡情况进行了测定。到20世纪70年代，即改用地表水20年后，发现白人女性尿路癌死亡率有所上升，而白人男性则未出现相应上升。非白人人口未发现明确趋势。总体而言，尚未证明改用氯化地表水会对尿路癌产生有害影响。
