Fleisher J M, Jones F, Kay D, Stanwell-Smith R, Wyer M, Morano R
Centre for Research into Environment and Health, University of Wales, UK.
Int J Epidemiol. 1993 Aug;22(4):698-708. doi: 10.1093/ije/22.4.698.
All previously published epidemiological studies of the health effects of bathing in marine waters contaminated with domestic sewage contain three major methodological weaknesses in study design: (1) failure to control for the substantial amount of temporal and spatial variation in indicator organism densities shown to occur within just a few hours at marine water bathing locations; (2) failure to relate indicator organism density directly to the individual bather; and (3) failure to rigorously control for non-water-related risk factors on previously reported associations between bathing in marine waters and illness among such bathers. We report the results of two intervention follow-up studies specifically designed to address these methodological weaknesses. We restricted study outcome to bathing-associated gastroenteritis since this is the illness most consistently reported to be associated with bathing in marine waters, and upon which both current US Marine Water Quality Criteria and other standards used worldwide are based. Our results show that faecal streptococci was the only indicator organism to predict the occurrence of gastroenteritis among bathers, and this occurred at only one of the three water quality sampling depths used in our study. The consumption of three different foods known or suspected to act as vectors in the transmission of gastroenteritis, as well as one non-food, non-water-related risk factor for gastroenteritis were found to significantly increase the risk of gastroenteritis among bathers. Multiple logistic regression modelling showed that these non-water-related risk factors confounded the relationship between exposure to marine waters of varying faecal streptococci densities and the occurrence of gastroenteritis among bathers to a moderate degree. Moreover, these analyses showed that the risk of gastroenteritis to the individual bather caused by these non-water-related risk factors, approximated the risk of gastroenteritis among bathers exposed to waters containing relatively high faecal streptococci densities. The implications of these findings with regard to the validity of present marine water quality criteria and on the need for, and design of, future epidemiological studies of bathing water associated illness are discussed.
此前所有已发表的关于在受生活污水污染的海水中沐浴对健康影响的流行病学研究，在研究设计上都存在三个主要方法学缺陷：（1）未能控制海水沐浴地点指示生物密度在短短数小时内出现的大量时空变化；（2）未能将指示生物密度直接与个体沐浴者相关联；（3）未能严格控制与水无关的风险因素，以研究此前报道的在海水中沐浴与此类沐浴者患病之间的关联。我们报告了两项干预随访研究的结果，这些研究专门设计用于解决这些方法学缺陷。我们将研究结果限定为与沐浴相关的肠胃炎，因为这是最常被报道与在海水中沐浴相关的疾病，并且当前美国海水水质标准以及全球使用的其他标准均基于此。我们的结果表明，粪链球菌是唯一能预测沐浴者肠胃炎发生的指示生物，且仅在我们研究中使用的三个水质采样深度中的一个深度出现这种情况。人们发现，食用已知或疑似在肠胃炎传播中充当载体的三种不同食物，以及一种与肠胃炎相关的非食物、非水风险因素，会显著增加沐浴者患肠胃炎的风险。多元逻辑回归模型显示，这些与水无关的风险因素在一定程度上混淆了不同粪链球菌密度的海水暴露与沐浴者肠胃炎发生之间的关系。此外，这些分析表明，这些与水无关的风险因素给个体沐浴者造成的肠胃炎风险，近似于暴露于粪链球菌密度相对较高水体中的沐浴者患肠胃炎的风险。本文讨论了这些发现对于当前海水水质标准有效性的影响，以及对未来与沐浴水相关疾病流行病学研究的必要性和设计的影响。
