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Health hazards vary greatly with different waters and their uses as well as with geography, climate, populations and their living standards. Only by defining practicable water quality objectives and priorities in the light of current knowledge and likely cost benefit can the risks of actual and potential disease be reduced to acceptable levels. These, however, will still vary in different parts of the world. Universal standards, in contrast to objectives, are still a long way ahead. In this paper, the British approach to the choice and use of bacterial indicator organisms in relation to potential health hazards and water quality criteria is reviewed briefly. Although no mandatory standards have ever been imposed, drinking water supplies in Britain are among the best in the world in quality and safety, even though about two thirds of them are derived directly from sewage polluted surface waters. However polluted these may be, in principle, they can be adequately treated, and British philosophy has always relied on this rather than on the more elusive targets of disinfecting sewage effluents and purifying water sources. For almost 50 years, coliform organisms and Escherichia coli have been used as the main indicators of fecal pollution, and, in this way, the efficiency of treatment and thus the safety of drinking water supplies have been effectively monitored. Despite increased water usage and recycling, there is no valid reason to change this view. Although viruses can be isolated readily from sewage effluents, there is no epidemiological evidence of transmission to man by the water route, and the current position is one of surveillance and research. Similarly, despite intensive investigation, there is no authenticated evidence of significant disease attributed to sewage polluted bathing beaches or efficiently maintained swimming pools. Aesthetic values, however, are now playing a greater role in environmental pollution control. In addition, compliance with microbiological and other standards for water for abstraction as well as for bathing recently accepted by the European Economic Community will be necessary in the future.
bacteria, water, coliform bacteria, pollution, disease
Consultant bacteriologist and directorchairman, Public Health Laboratory, Royal Cornwall HospitalStanding Subcommittee on the Bacteriological Examination of Water Supplies, Public Health Laboratory Service, Truro, Cornwall