The Health Risks of Bathing in Recreational Waters: A Rapid Evidence Assessment of Water Quality and Gastrointestinal Illness

Abstract

The European Bathing Directive (2006/7/EC) stipulates water quality standards for recreational bathing waters based on specified limits of 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 European Bathing Directive (2006) is to be reviewed in 2020. We conducted a rapid evidence assessment on recreational bathing waters and gastrointestinal illness (GI) to identify the extent of the literature published since the previous review period in 2003 and to determine whether there is any new evidence which may indicate that a revision to the Directive would be justified. Overall, 21 papers (from 16 studies), including two RCTs, met the inclusion criteria; 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 among studies, providing a limited evidence base on which to assess the classification standards. Overall, there appears to be a consistent significant relationship between faecal indicator organisms and GI in freshwater, but not marine water studies. Given the apparent lack of relationship between GI and water quality, it is unclear whether the boundaries of the Bathing Waters Directive are supported by studies published in the post-2003 period. We suggest that more epidemiological evidence is needed to disprove or confirm the original work that was used to derive these boundaries for marine waters.