The purpose of this study was to evaluate the risk of exposing bathers to human pathogens in sub tropical recreational marine waters with non-point source of sewage and other pollutants. The authors also examined possible relationships between microbial densities and random symptoms in human subjects by questioning bathers at random and following up with microbial monitoring.
A group of regular adult bathers were recruited and divided into two separate groups : bathers and non bathers. Bathers were required to spend 15 minutes in knee deep water across the beach and submerge their heads every 5 minutes. Water samples were also collected by the bathers which were assayed for enterococci by membrane filtration. The non bathers group were not allowed to enter the water and were restricted to sitting on a plastic seat in a covered roped off area distant from water and sand exposure for 15 minutes at a time. This was followed up 7 days later with a phone questionnaire to determine if any of the bathers and non bathers had any illnesses.
From the water sampling it was determined that all bathers were exposed to an average of 71 enterococci/100ml of water however there was a very large range between samples. Symptoms reported after a week included gastrointestinal, skin, eye and ear infections which would normally be associated with exposure to contaminated bathing waters. Bathers reported more gastrointestinal, respiratory and skin infections compared to the non-bathers group and also reported a significantly shorter onset time of illness.
This paper confirms that people bathing are more likely to acquire infections from subtropical recreational marine waters compared to those that do not bathe even when there is no source point.
It was also found that the skin illnesses reported were dose dependant, as expected, however there was no relationship between the degree of exposure to enterococci and severity of the respiratory and gastrointestinal infections with the causative agents unknown. This could have further implications as, currently, many U.S. authorities monitor water systems using gastrointestinal illnesses as an indicator to water quality. Therefore, if there is no direct correlation between dose and outcome of gastrointestinal illness, the advice given by these authorities may not be completely accurate.
Although this was the first paper of its kind, all the participants were previously healthy adults and does not represent children or anyone with a compromised immune system.
A review of: Fleisher, J.M., et.al.; 2010; The BEACHES Study: health effects and exposures from non-point source microbial contaminants in subtropical recreastional marine waters; Int. J. Epidemiol.; 39(5): pp1291-98.
3 comments:
I LOVE the title!
This paper really highlights the need for a re-evaluation of how indicator species are investigated to determine the safety of bathing water.
I agree with Matt about the title - nice!
This is an interesting paper with interesting methods - I'm not sure I'd want to be one of their participants myself...
It's pretty scary that you the monitoring systems don't actually give you a good indicator of how dangerous bathing water can be. It really suggests that something needs to change here to maintain our safety in the water.
Great title!
This was a great paper to read, and was a real eye opener to the flaws posed by the existing monitoring systems.
I do have to agree with Jennifer about the methods, taking a new route with this one! However, I believe that as subjects were directly assessed and treated as individuals, it gives a much better figure as to the dangers faced by bathers and non bathers alike.
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