EPIBATHE - Relationships between water quality and health outcomes

EPIBATHE aimed at identifying the relationship between microbial indicators and health outcomes in different bathing water bodies. In order to elucidate the relationships between water quality and health outcomes, eight different trials were carried out in Hungarian and Spanish water bodies. A group of volunteers, split into bathers and non-bathers, was interviewed and subsequently invited to bathe in selected water bodies. Six marked zones were differentiated. During the bathing, water quality was monitored by an in situ bio sensing device, measuring enterococus, Escherichia coli, coliphage, and other viruses. Samples were taken in each of the selected zones at 20 minutes intervals. Bathers stayed in their attributed zone for 10 minutes intervals. As a consequence, a bathing place and time could be attributed to each bather, and a three hour exposure period could be covered. After the exposure period, people were interviewed to determine any relationship between water quality and health symptoms. Obtained results were compared to previous trials carried out in Germany and United Kingdom, thereby obtaining a dataset which covered 7 thousand volunteers for a time period of 18 years (from 1989 to 2007).

Risk of gastroenteritis was analysed through different ways; not only the obtained data in Hungarian and Spanish bathing waters were analysed, but also a meta-analysis of exposure trials in four European countries was carried out. Moreover, E. coli was tested as indicator of gastroenteritis. The risk of non-enteric diseases from European recreational bathing water and the effects of non-water related risks were also studied. Bathing waters were compliant with the EU bathing Water Directive (1976), so they have low pollution levels. Consequently, although an increase in health symptoms (especially gastrointestinal symptoms) has been observed after bathing, the rates were lower in the present project than in previous studies. This result can be attributed to an improvement in health status and water treatment efficiency over the last decades in Europe. In addition, enterococci and E. coli have been identified as the most suitable predictor for gastrointestinal symptoms in marine and fresh waters, respectively.

Analysis of results showed that a review of water quality standards could be needless, in opposition to World Health Organisation (WHO) and European Union suggestions. Nevertheless, some microbiological methods defined in the revised Bathing Water Directive (2006) have been shown to be limited, since sometimes false positives were detected. In addition, risk assessment assumed that enterococci concentration in marine waters and gastroenteritis rates in bathers had a linear relationship. This assumption has little sense when data from different sites and times have been considered, and therefore a meta-analysis was necessary. Linear relationships were finally replaced with statistical distributions (stochastic models). This new approach has been validated in an International Workshop that took place in the WHO Headquarters in Geneva.

Assessment of human health effects caused by bathing waters. Accessible Report.