The EU Bathing Water Directive. Risk assessment and standards

In an attempt to reduce the risk of infection in natural bathing waters the European Union is in the process of improving the Bathing Water Directive 76/160/EWG, which regulates the safety of such waters. The proposal contains several positive innovations which will improve the protection of the bathers: (1) health-related indicators, (2) harmonized detection methods, (3) requirements for active bathing water management, and (4) stricter standards for coastal waters. One of the most salient features of the current draft is the introduction of bacterial standards that are more stringent for coastal than for fresh waters. This decision on different standards seems unjustified: it was taken solely on the grounds that in two epidemiological studies-one carried out in coastal, the other in fresh waters-the maximum excess rate of gastroenteritis among bathers in coastal waters was higher than among bathers in fresh waters. However, it was not taken into account that the concentrations of bacterial indicators at which the gastroenteritis rate began to increase was nearly identical in both studies. The ratio between the standard concentrations of E. coli and intestinal enterococci in the draft was set at 2.5. This value does not correspond to the ratio found in German surface waters with low pollution levels, with ratios ranging from 2.7 to 4.0, and to the even higher ratios found in raw and treated sewage effluents. As a consequence in a majority of cases the non-compliance of bathing waters in Germany would be caused exclusively by a violation of E. coli standards. In assessing risks of infection it must also be taken into account that the adequacy of E. coli and intestinal enterococci for signaling the presence of viruses in water is far from optimal. The decay of viruses in water-estimated by the decay of bacteriophages-was found to be substantially slower than the die-off of indicator bacteria.