Estimates of the severity of illnesses associated with bathing in marine recreational waters contaminated with domestic sewage

Abstract

Background. During the summers of 1989-1992 we conducted four randomized intervention trials at four separate UK bathing locations judged of acceptable quality under current USEPA and EU criteria. The results showed bathers to be at increased risk of gastroenteritis, acute febrile respiratory illness (ICD-9 461-466, 480), ear and eye infections relative to non-bathers. The public health significance of these findings has been questioned based upon the unproven assumption that these illnesses are minor in nature and thus of questionable public health significance. Methods. The severity of these illnesses or ailments in terms of duration of illness, percentage of participants seeking medical treatment, and number of days of lost normal daily activity among study participants reporting specific illnesses or ailments were assessed. In addition the attributable proportion of illness among the exposed (bathers) was calculated for each illness or ailment. Results. Average duration of illness ranged from approximately 4 days to approximately 8 days depending on the specific illness reported. The percentage of study participants seeking medical treatment ranged from 4.2% to 22.2% while the percentage reporting the loss of at least one day of normal daily activity ranged from 7.0% to 25.9% depending on the illness reported. The overall percentage of each illness that can be directly attributable to exposure to marine waters contaminated with domestic sewage ranged from a low of 34.5% for gastroenteritis to a high of 65.8% for ear infections. Conclusions. To our knowledge, this is the first study to assess and report the severity of illnesses associated with bathing in recreational waters contaminated with domestic sewage. Illness associated with bathing in marine waters contaminated with domestic sewage can no longer be viewed as minor, and indeed can have a substantial impact on the public health.