Association between swimming pool operator certification and reduced pool chemistry violations Nebraska, 2005-2006

Journal of Environmental Health, April, 2009 by Bryan F. Buss, Thomas J. Safranek, Julie M. Magri, Thomas J. Torok, Michael J. Beach, Brett P. Foley

To evaluate pool inspections with regard to pH, the frequency of pH violations for nonmunicipal, Class B pools was first calculated statewide and then by county. Inspections between Douglas County and Lincoln Class B pools were then compared. Water quality reports from public water systems were available in these locations to describe chemical properties of the water supplied by these sources. Prevalence of pH violations is affected by the pH and alkalinity of source water entering pools. Accordingly, to control for potential differences in pH of source water, analyses of pH violations were limited to selected cities in Sarpy County and all of Douglas County. These locations share a metropolitan utilities district and have a common surface-water source for all or the majority of pools. Inspection reports from Sarpy County cities that do not share this water source were excluded. Unlike Douglas County, Class B operator certification is not required in Sarpy County, which is the location of the disease outbreak (CDC, 2007). To evaluate pH violations (pH < 7.2 or pH > 7.8) alone and concurrent pH and free chlorine violations, Class B pool inspections in Douglas County were first compared with those in the selected Sarpy County cities. Class B inspections were then compared with Class A inspections within selected Sarpy County locations only.

Because pools were not inspected with equal frequency, multivariable analysis was performed by using logistic regression to control for frequency of inspection. Adjusted odds ratios were calculated to determine if conclusions on the basis of crude prevalence ratios (PR) alone would change substantially.

Results

This study identified 2,010 routine inspections from 894 Nebraska pools (Table 1). Of these, 214 pools had one inspection and 680 had more than one inspection per pool (median: 2; range: 1-7). In counties without Class B operator certification requirements, Class B pool inspections were more likely (30.9%, 167 of 541) than Class A (13.0%, 60 of 460) to have free chlorine violations (PR = 2.4, 95% confidence interval [CI] = 1.8-3.1). When comparing Class B pool inspections only, free chlorine violations were more likely in counties without (30.9%, 167 of 541) Class B operator certification requirements than in counties with (15.8%, 138 of 876) requirements (PR = 2.0, 95% CI = 1.6-2.4).

TABLE 1
Number of Pools and Routine Inspections by Class Designation and
Operator Certification Requirements

Class B Operator  Number of Pools   Number of Routine
Certification        by Class      Inspections by Class
Requirements
                   A    B   All     A      B    All
       Yes         59  367  426    133    876  1,009
        No        221  247  468    460    541  1,001
      Total       280  614  894    593  1,417  2,010

Of 1,417 statewide Class B pool inspections, 210 (14.8%) reported a pH violation. Of these, 153 (72.9%) occurred in two counties (Douglas and Sarpy). The majority of cities in these counties share a metropolitan utilities district. During 2005-2006, the reported ranges for more than 99% of water supplied from this source were approximately 8.8-9.0 for pH and 83-140 ppm for alkalinity (Metropolitan Utilities District, 2005 & 2006). A water quality report for comparison was also available for the city of Lincoln. In contrast to high pH surface water used by pools in Douglas County, pools in Lincoln use groundwater with pH and alkalinity approximately 7.7 and 188 ppm, respectively (Lincoln Water System [LWS], 2006). Of 876 inspection reports from all Class B pools in these two locations that require trained certified operators, 115 had pH violations. Of these, inspections from pools in Douglas County (n = 580) accounted for 93.0% (107 of 115), and only 7.0% (8 of 115) occurred in Lincoln (n = 296). The majority of pH violations were low (<7.2), indicating overcorrection by operators.