Health risks of bathing waters: Links between gastrointestinal illness and marine bathing

The 2006/7/EC European Bathing Directive stipulates water quality classification standards for recreational bathing waters based on specified limits for Faecal Indicator Organisms (FIOs). Presence of FIOs above the limits is considered to be indicative of poor water quality and to present a risk to bathers’ health. The health risks most closely associated with bathing are faecal-oral diseases which cause gastrointestinal illnesses (GI) such as diarrhoea and vomiting. The European Bathing Directive is due to be reviewed in 2020. Defra commissioned this rapid evidence assessment (REA) on recreational bathing waters and GI to identify the extent of the literature published since the previous review (the 2006/7 standards were based, in part, on World Health Organization (WHO) evidence published in 2003), and to determine whether there is any new evidence which may indicate whether or not a revision to the Directive would be justified. Data was identified and extracted from 21 relevant papers (from 16 studies) published since 2003; 12 were conducted in marine waters and four were conducted in freshwater. Considerable heterogeneity existed between study protocols and the majority had significant methodological limitations, including self-selection and misclassification biases. Moreover, there was limited variation in water quality between studies. In particular, few studies were conducted in ‘poor’ water quality, and none were conducted in ‘sufficient’ water, thus providing a limited evidence base in which to assess the classification standards.