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Gastrointestinal symptoms among swimmers following rain events at a beach impacted by urban runoff
Citation:
Wade, Tim, R. Converse, E. Sams, A. Williams, E. Hudgens, AND A. Dufour. Gastrointestinal symptoms among swimmers following rain events at a beach impacted by urban runoff. Presented at Society for Epidemiological Research, Boston, MA, June 18 - 21, 2013.
Impact/Purpose:
Evaluation of the occurence of diarrhea following rain events at a beach impacted by stormwater runoff
Description:
Gastrointestinal symptoms among swimmers following rain events at a beach impacted by urban runoff Timothy J. Wade, Reagan R. Converse, Elizabeth A. Sams, Ann H. Williams, Edward Hudgens, Alfred P. Dufour Gastrointestinal symptoms among swimmers have been associated with fecal contamination at beach sites impacted by discharges of human sewage. Rainfall and storm water runoff can transport pollutants, including fecal contaminants, into beach water. We investigated the association between diarrhea among swimmers and rain events at a beach in South Carolina impacted by runoff. During the summer of 2009, we enrolled and interviewed 11,159 beachgoers. We obtained information about swimming exposures and we then contacted them by telephone 10-12 days later to ascertain the incidence of diarrhea (3 or more loose stools in a 24 hour period) and other symptoms. Rainfall was measured using an on-site rain gauge. There was at least some rainfall within the previous 24 hours (1-day lag) and within the 24-48 hours (2-day lag) for 12 and 14 of the 29 study days, respectively. Rainfall was classified as none; low-moderate (<=0.39 inches); or high (>0.4 inches, 90th percentile). Unadjusted incidence of diarrhea was 3.0%, 4.0%, 4.4%, and 6.5% among non-swimmers; swimmers (body-immersion) following no rainfall in the previous 24 hours; swimmers following low-moderate rainfall and swimmers following high rainfall, respectively. Adjusted Odds Ratios and 95% Confidence Intervals compared to non-swimmers were: 1.33(0.95-1.86); 1.55(1.07-2.25); and 2.14(1.32-3.48) for swimmers with no rainfall, low, and high rainfall in the prior 24 hours, respectively. There was also a significant trend across categories among swimmers (p=0.003). Rainfall the day of swimming and during the 24-48 hour lag were not as consistently associated with diarrhea. In conclusion, diarrhea in swimmers was associated with rainfall in the 24 hours prior to swimming at a beach impacted by urban runoff. This abstract does not reflect EPA policy.