An Assessment of Disinfection-Related Water Chemistry at Public Pools and Spas in Louisville, Kentucky.

Author:Gerdingi, Thomas


With more than 7.4 million swimming pools in the U.S. as of the mid-2000s (Otto, 2006) there are typically between 300 million and 350 million swimming instances occurring annually in the U.S., making swimming one of the top four recreational activities in the U.S. (Otto, 2006; U.S. Census Bureau, 2009). With a substantial proportion of the U.S. population using pools, an accompanying substantial number of recreational water illnesses (RWIs) have been documented, including 27,219 illnesses and 8 deaths attributable to 493 reported outbreaks of RWIs from treated recreational water environments from 2000-2014 (Hlavsa, Kunz, & Beach, 2017). The frequency of RWIs is underestimated by outbreak reporting alone, as many RWIs are one of the following: not reportable conditions, not severe enough in affected patients to seek clinical evaluation, not able to be associated with recreational water exposure, and/or not part of a reported recreational water-related outbreak.

Effective pool management decreases the risk of users contracting RWIs. In studies examining 22,131 and 84,187 pool inspections in the U.S. from 2002 and 2013, respectively, 8.3% and 12.3% of the inspections warranted immediate closure of the pool being inspected (Centers for Disease Control and Prevention [CDC], 2003; Hlavsa et al., 2016). The most frequent violations observed in both studies were related to disinfection inadequacies specifically pertaining to disinfectant concentrations, pH, and chemical feeders. Inadequacies pertaining to pool disinfection can present harmful chemical exposure opportunities or enhance the survivability and/or growth of pathogens including but not limited to Pseudomonas aeruginosa, Cryptosporidium, Giardia, norovirus, and toxigenic E. coli (Black, Keirn, Smith, Dykes, & Harlan, 1970; Hlavsa et al., 2015; Seyfried & Fraser, 1980; Shields, Gleim, & Beach, 2008). Therefore, inadequate adherence to sound disinfection protocols enhances risks for respiratory, ocular, and cutaneous ailments among pool visitors and workers (Fantuzzi et al., 2010; Nickmilder & Bernard, 2007). Furthermore, swimmer shedding of microbial flora (including potential pathogens) occurs in aquatic environments (Gerba, 2000; Smith & Dufour, 1993) and when coupled with insufficient disinfection, this situation presents an increased infectious disease risk to recreators. Studies on untreated recreational waters have demonstrated a positive association between densitites of fecal indicator organisms in water and the risk of experiencing a swimming-associated gastrointestinal illness (Pruss, 1998; Wade, Pai, Eisenberg, & Colford, 2003), and this risk is greater when the contamination is of human origin (Soller, Schoen, Bartrand, Ravenscroft, & Ashbolt, 2010).

An analysis of treated recreational water-associated outbreaks by Hlavsa and coauthors (2017) indicates that the leading setting associated with 32% of the outbreaks from 2000-2014 were within hotel environments. Data on the population size recreating in hotel environments could be unknown, which limits recreational water-associated illness risk comparisons with other settings. Furthermore, among outbreaks with unidentified etiologies, hotel settings were linked to 56% of these 108 outbreaks between 2000 and 2014 (Hlavsa et al., 2017). In 2016, it was noted that studies on inspection failures could hold some utility for understanding setting-specific intervention opportunities that might reduce setting-specific RWIs including outbreaks; however, these types of data analyses were not possible due to their inspection forms and subsequent data being limited to pool category and not including setting (Hlavsa et al., 2016). Upon using data with pool setting documented, as done in a Georgia statewide analysis (N = 4,441), hotels and motels (n = 1,133) led the state in noncompliance related to disinfection residual concentrations and pH levels with 287 and 205 violations, respectively. In comparison, subdivision pools were the most numerous setting type in the 2014 Georgia database (n = 1,179) and had 113 and 64 events related to noncompliance in the disinfection residual concentrations and pH levels, respectively (Shack, Redmond, & Rustin, 2016).

While there has been much evidence published on the relationship between improperly managed swimming facilities, bacterial growth, and its association to outbreaks of RWIs, little research exists demonstrating the role of pool setting and how local health departments (LHDs) can tailor educational interventions with their business sectors and various pool operators so together they can be partners in protecting and promoting public health while preventing disease. Prior to developing sector-specific interventions related to pool health, data can help inform need. In this study, based upon prior observations reported in the literature, it was hypothesized that hotel swimming pools would be at greater risk for inspection failure than other settings and thus could be an area or sector whereby future in-depth study or tailored interventions might be warranted.


During summer 2018, data were collected from approximately one third of the public pools present in the Louisville metropolitan area of Jefferson County, Kentucky. Overall, 143 locations, many with more than one body of water (venue), were visited once per week from the end of May 2018 until the middle of August 2018. Each location was visited on the same day of the week, excluding days with inclement weather. During each visit, the pH, free chlorine, and alkalinity were screened using a LaMotte Insta-Test test strip. If free chlorine levels were out of range after the screening, either...

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