Contact with Beach Sand and Risk of Illness

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  • March 22, 2019
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  • Heaney, Christopher D.
    • Affiliation: Gillings School of Global Public Health, Department of Epidemiology
Abstract
  • Background: Recently, numerous studies of fecal contamination of beach sand have shown that beach sand can harbor higher concentrations of fecal indicator organisms than nearby recreational waters. Although fecal pathogens have also been isolated from beach sand, the risk of illness associated with beach sand contact and fecal indicator organism concentrations in sand is unclear. Methods: During 2003-2005 and 2007, beach visitors at 7 U.S. beaches were enrolled in the study and asked about sand contact the day of their beach visit. Ten to 12 days later participants were telephoned to answer questions about health symptoms experienced since the visit. At 2 study beaches in 2007, beach sand was analyzed for concentrations of the fecal indicators Enterococcus, Bacteroides, B. thetaiotaomicron, and F+-specific coliphage. Results: We completed a total of 27,365 interviews at 4 freshwater and 3 marine water beaches. Sand contact was strongly associated with age, water contact, and beach. After controlling for age, sex, water contact, race/ethnicity, and beach, digging in the sand was positively associated with gastrointestinal (GI) illness (aIPR=1.14; 95% CI 1.02-1.26) and diarrhea (aIPR=1.20; 95% CI 1.05-1.36). The point estimate was slightly stronger between being buried in the sand and GI illness (aIPR=1.22; 95% CI 1.04-1.42) and diarrhea (aIPR=1.23; 95% CI 1.01-1.51), respectively. Similar effects were observed among nonswimmers digging in sand for GI illness (aIPR = 1.26; 95% CI = 1.03-1.55) and diarrhea (aIPR = 1.26; 95% CI = 0.98-1.62). Stronger associations were observed among those getting sand in their mouth for GI illness (aIPR=1.82; 95% CI 1.19-2.78) and diarrhea (aIPR=1.65; 95% CI = 0.96-2.84). Non-enteric illnesses were not consistently associated with sand contact. Variation was observed in beach specific results suggesting site-specific factors may be important in the risk of illness following sand exposure. At 2 marine beaches 144 sand samples were analyzed for fecal indicators and 4,999 interviews were completed. A molecular measure of Enterococcus in sand (qPCR CCE/g) was positively associated with GI illness among those digging in sand (aOR per log increase in qPCR CCE/g=1.45; 95% CI 1.05-2.01) and buried in the sand (aOR = 3.12; 95% CI 1.08-9.05). The relationship between other sand fecal indicator measures with GI illness was not consistent. Conclusions: Contact with beach sand was positively associated with enteric illness at beach sites but there was variability in the effect by beach. This study demonstrated a positive relationship between sand contact activities and GI illness as a function of microbial sand quality.
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  • ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Epidemiology, School of Public Health.
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  • Wing, Steve
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