EPIDEMIOLOGIC-STUDY OF SWIMMING-ASSOCIATED ILLNESSES RELATING TO BATHING-BEACH WATER-QUALITY

The water quality objective or indicator of bathing beaches is establi shed on the basis of epidemiological data of swimming-related illnesse s in the local population. It needs to be updated and refined in light of changes in the composition, health status and recreational activit ies of the community. A major epidemiological study was conducted in H ong Kong in 1992 involving interviewing 25000 beach-goers on the healt h effects of exposure to bathing water. The results indicated that the total incidence of swimming-related illness symptoms was 41 per 1000, higher than the 30 per 1000 found in 1987. Eye, skin and respiratory symptoms were 2-20 times more prevalent in swimmers than in non-swimme rs. Only gastrointestinal (GI) symptoms were directly related to the p ollution level and bacterial content of beach water. Turbidity of beac h water was closely linked with GI and highly credible GI symptoms and might be used as a monitoring tool and a parameter in the beach water quality objective. There was also a direct correlation between GI sym ptoms and the number of Clostridium perfringens, Aeromonas spp., Vibri o cholerae (non-Ol) in beach water. No direct relationship between GI symptoms and E. coli or faecal coliforms could be identified in this s tudy.