enterococci level or a binary contaminated/ not contaminated variable) with our candi- date independent variables of precipitation (lagged up to 1 week), beach, station (if there were multiple sampling sites at a given beach), and water temperature (lagged up to 1 week). This modeling identified 2-day pre- cipitation (i.e., the sum of precipitation on the day of sampling and the day before sam- pling) as the primary predictor of enterococci levels in each town. We then performed a cut point analysis by calculating the sensitivity, specificity, and Youden Index of cut points in 0.1-in. incre- ments of 2-day precipitation. The Youden Index balances sensitivity (e.g., the abil- ity to detect a beach contamination event) and specificity (e.g., the ability to detect the absence of a beach contamination event), which is appropriate for evaluation of dichot- omous diagnostic testing such as the deci- sion to close or not close a beach for a given rainfall event. The recommended cut point for preemptive closure was then selected by comparison of the positive predictive value of cut points associated with local Youden Index maximum values. In Branford and East Haven, we recom- mended preemptive beach closure following 2.3 in. of 2-day rainfall, whereas in Guilford we recommended closure at 1.0 in. (Table 1). As the lag between sample collection and beach closure is >24 hr in these towns, these guidelines are anticipated to meaningfully decrease exposure of bathers to contaminated water. We did not recommend a preemptive closure threshold for Madison due to an insuf- ficient number of exceedance events to model. Branford and East Haven implemented pre- emptive beach closure at 2 in. Preemptive closure is not a cure-all. Beach closure is a policy balancing act between maintaining beach accessibility by keeping beaches open and protecting bather safety with proper closures. Moreover, any rainfall cut point for preemptive closure will lead to both false negative and false positive closure decisions. Preemptive closure rainfall thresh- olds do not reflect other factors influencing contamination (e.g., tides, known contami- nation events such as sewage bypasses), and in addition to using rainfall thresholds, clo- A Local Response: Preemptive Closure
TABLE 1
Summary of Recommended Preemptive Closure Thresholds for Beaches in the Towns of Branford, East Haven, Guilford, and Madison in Connecticut
Town
Preexisting Cut Point (in.)
Preemptive Closure Policy Adoption
Updated Cut Point (in.)
Branford
2.3 2.3 1.0
Yes Yes
2.0 2.0
East Haven
Guilford Madison
No
– –
–
–
Note. No recommended preemptive closure threshold was provided for Madison due to insufficient data and an insufficient number of exceedance events in the available records. Overall, two of the four towns implemented preemptive beach closure policies.
studied for decades (Kay et al., 1994; Pond, 2013), the local variability of contamination and diculty of screening for general symp- toms associated with fecal bacteria exposure complicate the development of practicable guidelines to limit health risks from recre- ational water exposures (Fewtrell & Kay, 2015; World Health Organization, 2003). Lit- erature review of epidemiological studies indi- cates that recreational water use is associated with gastrointestinal illness despite absence of reported outbreaks (Fewtrell & Kay, 2015). Children ≤10 years are at increased risk of gas- trointestional illness, potentially because chil- dren are apt to swallow water, transfer water from hand to mouth after exposure, or spend more time in recreational water than adults (Wade et al., 2008). The delay associated with water sampling, delivery of samples, and assay of the samples is a major limitation of the current protocol, but it could pose a greater threat of expo- sure to bathers in coming years. Given the expected increase in frequency of heavy pre- cipitation events and increased temperatures associated with climate change (U.S. Environ- mental Protection Agency [U.S. EPA], 2016), reliance on regular once-weekly sampling alone likely will become even more insu- cient to minimize bather contact with con- taminated waters. Preemptive beach closure—the shut- down of beaches following a rain event of predetermined rainfall intensity, duration, or amount—might be a solution to reduce bather exposure to probable high fecal bac- teria counts during the time lag period
between water sample collection and sample analysis and reporting (U.S. EPA, 2014). We note that to ensure safe water quality in shellfishing areas, in addition to conducting water sampling and testing for bacteria, it is standard practice to use preemptive closures based on 24-hr precipitation. Within Long Island Sound, all shellfish beds are closed with precipitation in excess of 3.0 in. Developing Preemptive Closure Thresholds To better understand current water sampling protocols and the use of preemptive beach closure by Connecticut towns with Long Island Sound beaches, we surveyed 15 local health departments. Overall, six departments closed their beaches when a sample was reported to be in exceedance, and beaches did not reopen until a negative resampling. Most respondents cited stormwater runo after a rain event as their greatest source of water contamination, but only three departments specifically sampled after heavy rain events. Preemptive closure thresholds were used by six health departments: Fairfield (1.75 in.), Norwalk (1.6 in.), Greenwich (2.5–3 in. except for Byram Beach), Darien (1 in.), Stratford (1 in.), and West Haven (1 in.). We then sought to develop preemptive clo- sure thresholds for four Connecticut coastal towns: Branford, East Haven, Guilford, and Madison. Using historical meteorological and water sampling data, we initially developed town-specific predictive linear and logistic models through stepwise regression, model- ing the dependent variable (i.e., continuous
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