Abstract and Introduction
Objectives: Chlorination destroys pathogens in swimming pool water, but by-products of chlorination can cause human illness. We investigated outbreaks of ocular and respiratory symptoms associated with chlorinated indoor swimming pools at two hotels.
Measurements: We interviewed registered guests and companions who stayed at hotels X and Y within 2 days of outbreak onset. We performed bivariate and stratified analyses, calculated relative risks (RR) , and conducted environmental investigations of indoor pool areas.
Results: Of 77 guests at hotel X, 47 (61%) completed questionnaires. Among persons exposed to the indoor pool area, 22 (71%) of 31 developed ocular symptoms [RR = 24 ; 95% confidence interval (CI) , 1.5-370], and 14 (45%) developed respiratory symptoms (RR = 6.8 ; 95% CI, 1.0-47) with a median duration of 10 hr (0.25-24 hr) . We interviewed 30 (39%) of 77 registered persons and 59 unregistered companions at hotel Y. Among persons exposed to the indoor pool area, 41 (59%) of 69 developed ocular symptoms (RR = 24 ; 95% CI, 1.5-370) , and 28 (41%) developed respiratory symptoms (RR = 17 ; 95% CI, 1.1-260) with a median duration of 2.5 hr (2 min-14 days) . Four persons sought medical care. During the outbreak, the hotel X's ventilation system malfunctioned. Appropriate water and air samples were not available for laboratory analysis.
Conclusions and relevance to professional practice: Indoor pool areas were associated with illness in these outbreaks. A large proportion of bathers were affected ; symptoms were consistent with chloramine exposure and were sometimes severe. Improved staff training, pool maintenance, and pool area ventilation could prevent future outbreaks.
Swimming is a popular activity and sport among people of all ages. Outbreaks of illness caused by infectious organisms associated with swimming pool use are reported with regularity (Yoder et al. 2004). Proper pool maintenance, especially appropriate water disinfection procedures, and monitoring of pool water quality are key factors in the prevention of infectious diseases associated with use of swimming pools (Nemery et al. 2002). However, although chlorine kills many potential pathogens, it can also react with human wastes such as perspiration, urine, skin particles, and lotion in pool water to form chloramines and trihalomethanes. Chloramines may remain in the pool water or volatilize into the air, where they create the pungent smell and acutely irritating properties of air above swimming pools (Aggazzotti et al. 1990; Goyder 2000; Hery et al. 1995).
Chloramines have been suspected as a cause of occupational asthma and pneumonitis among lifeguards (Massin et al. 1998; Nemery et al. 2002; Thickett et al. 2002). Also, an outbreak associated with a swimming pool and attributed to chloramine exposure led to cough or ocular symptoms in > 70% of pool patrons interviewed (Goyder 2000). Chloramine levels in pool water depend on chlorine and nitrogen concentrations, pool pH, temperature, and water circulation patterns (Hery et al. 1995; Massin et al. 1998; Nemery et al. 2002). However, chloramine levels in the air above swimming pools are also influenced by ventilation and the pool water chemistry (Hery et al. 1995; Massin et al. 1998). Indoor pools are likely to be less well ventilated than outdoor pools, so the risks associated with chloramine exposure are likely to differ between indoor and outdoor swimming pools.
We investigated two outbreaks of acute ocular and respiratory symptoms associated with exposure to indoor swimming pools. In January 2004, the Illinois Department of Public Health was notified of two outbreaks of acute ocular and respiratory symptoms associated with indoor swimming pool exposure among patrons of two hotels located in noncontiguous central Illinois counties. We investigated these outbreaks during January 2004 to describe illness syndromes, determine risk factors for illness, and develop recommendations to prevent future incidents.