New information on health risks linked to bathing and consequences on regulation and prevention
Many recent prospective epidemiological studies (CABELLI, 1980 - EPA - of different marine waters, DUFOUR, 1984 - EPA - of lake waters, and CAREPS, 1987 - FRANCE - of a river water), give the same concordant results : the main health risks linked with bathing in waters contamined by municipal wastewater discharges are gastro-intestinal illnesses. In all studies, a consistent correlation was established between this kind of disease and fecal streptococci concentration but there are few or no correlations with the two parameters (fecal and total coliforms), used at present, to establish the required quality of recreational waters. Consequently, fecal streptococci, usually considered as fecal contamination indicators are also health risk indicators and they should be used as parameters for the assessment of pollution of natural waters, for the efficiency of treatment processes and for the quality of recreational waters. Obviously, regulations in European countries are at present based on the control of the level of fecal contamination and this is correct if occasional risks due to eventual diseases among populations are to be avoided; in fact, the systematic health risk must be taken into account and hence fecal streptococci should be used as a controlling parameter. Guide and imperative values of the European directive are not justified by epidemiological studies : rates of objective gastro-intestinal complaints in populations of bathers, are at the same level (around 15 p 1000), for the quide value in fecal streptococci (100 FS/100 ml) and the imperative value in fecal coliforms (2000 FC/100 ml). Corresponding rates in populations of "non bathers" are around 4.5 p 1000 (a French study). Moreover for the same levels of differents parameters these rates are not the same in marine waters and in freshwaters. The same values for the two types of waters are questionable. Skin diseases constitute another health risk, but the different studies have brought no definite answers to the problems of the sources of the diseases : these sources could be wastewaters of domestic origin, interhuman contamination during bathing or the natural characteristics of the water, such as the presence of particular germs. A relevant controlling parameter for this kind of health risk has net yet been found.