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A repeated-measures study of recreational water exposure, non-point source pollution, and risk of illness
Citation:
Lin, C., C. Heaney, Tim Wade, R. Noble, AND S. Wing. A repeated-measures study of recreational water exposure, non-point source pollution, and risk of illness. Presented at Society for Epidemiologic Research, Boston, MA, June 17 - 20, 2013.
Impact/Purpose:
Discharge of stormwater runoff onto beaches is a major cause of beach closings and advisories in the United States. This study investigated the chronic health effects among a cohort of lifeguards and surfers at beaches impacted by stormwater
Description:
Discharge of stormwater runoff onto beaches is a major cause of beach closings and advisories in the United States. Prospective studies of recreational water quality and health have often been limited to two time points (baseline and follow-up). Little is known about the risk of illness from repeated seasonal water exposure. We conducted a repeat-measures study to examine the risk of illness associated with regular water exposure that could be potentially affected by stormwater runoff in the northern Outer Banks of North Carolina. We enrolled adult surf instructors and lifeguards in the summer, 2011 and followed them for an average of 7 weeks (maximum=14). Participants (n=38) provided daily reports of water exposure (e.g., swimming, head immersion, swallowing water) and self-reported illness symptoms (gastrointestinal, upper respiratory, ear, skin, eye) on weekly follow-up surveys. To assess exposure to fecal contamination, we measured enterococci and recorded daily precipitation and time since a storm event. We used conditional fixed-effects logistic regression to compare within-person variation of illness to water activities, precipitation, and enterococci levels. Compared to having no water exposure, water exposure in the presence of any enterococci (adjusted odds ratio, aOR=1.65; 95% confidence interval, 95% CI 0.82-3.34) appeared to increase the odds of any illness on the same day more than in the absence of any enterococci (aOR=1.08; 95% CI 0.52-2.25). Any swimming in the antecedent 2 days was also associated with an increased odds of any illness (aOR=1.71; 95% CI 1.11-2.62). Ocean exposure and enterococci were associated with illness in workers with regular water exposure. Additional analyses will evaluate time lags between exposure and illness. This abstract does not necessarily reflect EPA policy.