Iowa Beach Study
Eric O'Brien, Janice Boekhoff: Iowa Department of Natural Resources
Peter Weyer, David Riley: UI Center for Health Effects of Environmental Contamination
Michael Wichman, Nancy Hall: University Hygienic Laboratory
Gregory Gray, Troy McCarthy, R. William Field, Tara Smith: UI College of Public Health
A prospective pilot study of beach users from three Iowa beaches was conducted in June-August 2005 to determine the number of self-reported gastrointestinal (GI) illness symptoms and skin irritation/rash symptoms in swimmers and non-swimmers, and to correlate those numbers with bacterial levels in beach water. Aims of the study were to determine GI illness and skin irritation/rash symptom numbers at freshwater beaches with nonpoint pollution sources and to evaluate the effectiveness of indicator bacteria as predictors of risk under unique lake conditions found in Iowa. Study staff visited beaches on a daily basis over six weeks to distribute study flyers, recruit participants and take water samples. One-thousand and thirty-nine people were recruited for the study. Of that number, 261 people participated on-line in a web-based system to collect baseline information, and completed follow-up surveys over four weeks which included questions about water activities, time spent at the beach, occurrence of GI illness or skin irritation, etc. Composite water samples were collected daily and analyzed at the University Hygienic Laboratory for E.coli, enterococci, and total microcystin toxin. Spearman correlation coefficients were calculated to compare beach indicator variables to GI illness and skin irritation/rash symptoms. Reported GI illness and skin irritation/rash episodes were correlated with indicator variables at each beach. Multiple regression analyses ranked beach indicator variables, bacterial levels in the water, and various interactions as risk factors for GI illness and skin irritation/rash episodes. Statistically significant associations between bacteria levels and reported illness included enterococci level and diarrhea at Beach 1, enterococci level and skin irritation/rash symptoms at Beach 2, and microcystin toxin level (<1 μg/L) and skin irritation/rash at Beach 1. The results of this pilot study indicate that more research is needed to determine if these associations exist on a larger scale at other inland beaches and to further explore the positive correlation between low levels of microcystin toxin and skin irritation/rash.
A poster titled Microcystin Toxin and Enterococci Indicator Levels Associated with Freshwater Recreational Waterborne Illness was presented at the 2007 American Society for Microbiology conference by Nancy Hall. Her powerpoint poster is available here: