A REANALYSIS OF DATA SUPPORTING UNITED-STATES FEDERAL BACTERIOLOGICAL WATER-QUALITY CRITERIA GOVERNING MARINE RECREATIONAL WATERS

Current U.S. federal bacteriological water quality criteria governing marine recreational waters are based solely on a mathematical relationship between enterococci density and gastroenteritis among swimmers reported in a large prospective epidemiological study conducted for U.S. EPA. Unfortunately, this epidemiological study contained serious methodological and analytical weaknesses. This report identifies some of these methodological weaknesses and presents a reanalysis of the data upon which the current federal marine water quality criteria are based. The reanalysis reported herein uses logistic regression modeling to estimate the probability of gastroenteritis occurring in the individual swimmer at different enterococci densities. The results of this reanalysis show the mathematical relationship between enterococci density and swimming-associated gastroenteritis derived by the EPA study to be of questionable validity so that current federal bacteriological water quality criteria governing marine recreational waters are not based on strong enough evidence to support their continued use.