'Clean' water may infect swimmers.
A swimmer's risk of developing either respiratory disease accompanied by fever or an ear infection rose in lockstep with increasing evidence of fecal contamination in seawater-even though the measured contamination never exceeded government limits.
"This demonstrates that even 'clean' beaches produce significant health effects," concludes David Kay of the University of Leeds in England, an author of the new report.
His team recruited 1,216 adults to visit one of four coastal beaches in England. Upon arriving, half of the volunteers learned they were to enjoy themselves without entering the water, while the rest had to spend some 10 minutes frolicking in the frigid waves, submerging themselves at least three times. Kay's team then took samples of the water where each swimmer had been playing.
Globally, most water quality limits or guidelines are based on counts of fecal coliform bacteria. The Leeds team tested their samples for these bacteria along with four others. Such gastrointestinal microbes, all considered harmless, serve as markers of fecal contamination, which includes other microbes, including viruses.
In the September American Journal of Public Health, Kay and his colleagues now report finding that respiratory disease in the swimmers was associated with their exposure to fecal streptococcus, a type of noncoliform bacterium.
This is the first study to link fecal strep with an infection other than gastroenteritis, observes Alfred P. Dufour of the Environmental Protection Agency in Cincinnati. Moreover, he says, the researchers identified the threshold contamination necessary to trigger those infections. For the flulike disease, that turned out to be 60 streptococci per 10 milliliters of water.
For gastroenteritis, the threshold was even lower.
In an earlier analysis by Kay's team, fecal strep also outperformed fecal coliform bacteria as a gauge of gastroenteritis risk (SN: 10/15/94, p. 255).
It now appears that if just one bacterial species is to be monitored, fecal strep would be the most useful one, says Jay M. Fleisher, a public health researcher at the State University of New York Health Science Center at Brooklyn and a coauthor of the studies.
In fact, Dufour notes, EPA published recommendations a decade ago arguing that, for regulatory purposes, fecal strep-also known as enterococci-are the best indicator of fecal contamination. To date, however, state regulators have all but ignored the recommendation.
In the new British study, ear infections correlated with the fecal coliform measurements but not with fecal strep. Fleisher interprets the data as arguing that a single marker of fecal contamination, whether coliform or strep bacteria, offers too little water quality information to protect public health.
"I agree that more than one indicator organism is needed to establish marine standards for recreational water quality," says Joan B. Rose, a water pollution microbiologist at the University of South Florida in St. Petersburg.
Better yet, she argues, health officials should monitor for the actual pathogens that cause disease. Says Fleisher, "We're trying, and it looks more and more like they are going to be viral agents."