Sewage contamination of coastal bathing waters in england and wales A bacteriological and epidemiological study

Abstract

1. Bacteriological surveys of more than forty popular bathing beaches around the coasts of England and Wales have been made during the past 5 years. The great majority of the beaches studied were subject to contamination with sewage.2. A rough grading of the beaches studied gave a similar ranking order whether the results of the presumptive coliform test or faecal coli counts were used as the basis of grading.3. Grading of beaches was valid only when surveys were carefully planned to ensure representative sampling from the areas on the beaches concerned where bathing actually took place.4. The coliform test as used in the bacteriological examination of drinking waters was the main test procedure used but had certain limitations. Promising results with plate counts on relatively non-inhibitory media were obtained.5. Various salmonella serotypes, notablySalm. paratyphi B, were isolated in small numbers from a high proportion of sea-water samples. The proportion of positive results for salmonella isolation increased from 13·3% in samples with less than 1000 coliform organisms per 100 ml. to 40·1% in samples with over 10,000 coliforms per 100 ml. Comparison of the numbers of salmonellae isolated with what is known of the minimum infective doses of these organisms suggested that very large volumes of sea water would require to be ingested for infection to occur.6. Poliovirus was not isolated from a small series of sea-water samples examined. Because of the very large dilution factor, special concentration procedures would probably be required to isolate this virus from sea water.7. Four cases of paratyphoid fever probably due to bathing were recorded. Surveys of the two associated beaches had given median presumptive coliform counts of more than 10,000 per 100 ml., and both showed gross macroscopic pollution with sewage.8. A statistically controlled study of the bathing histories of 150 poliomyelitis cases in children living permanently by the seaside gave no evidence that bathing had played any part in causing the disease.