Evaluation of water hygiene in public swimming places in Chongqing based on principal component analysis / 环境与职业医学

ABSTRACT

Background At present, the evaluation of water quality in public swimming places mostly adopts the single index evaluation method, ignoring the possible correlation between the indicators, the problem of information overlap between the indicators, and the differences between the swimming places with single or multiple unqualified water quality indicators. Objective To evaluate water quality in public swimming places in Chongqing objectively, intuitively, and comprehensively. Methods In 2020, a stratified random sampling method was used to investigate seven water quality indicators of 112 public swimming places in the central urban area, the new downtown urban area, the northeastern area, and the southeastern area of Chongqing. The selected indicators were free residual chlorine, turbidity, pH, free residual chlorine in disinfection pool of feet, urea, total plate count, and coliform bacteria. Principal component analysis was utilized to comprehensively evaluate water quality of swimming places by calculating principal component characteristic values and comprehensive evaluation values. Results The qualification rates of free residual chlorine, turbidity, pH, free residual chlorine in disinfection pool of feet, urea, total plate count, and coliform bacteria were 91.30%, 89.40%, 91.30%, 91.30%, 99.00%, 95.20%, and 86.50%, respectively, and the P50 values were 0.455 mg·L−1, 0.59 NTU, 7.352, 6.63 mg·L−1, 0.78 mg·L−1, 8 CFU·mL−1, and 0 CFU·100mL−1, respectively. The results of principal component analysis showed that KMO=0.573, P<0.001; four principal components were extracted, the eigenvalues of each principal component were 2.990, 1.624, 0.854, and 0.617, respectively, and the cumulative contribution rate was 86.928%. The comprehensive values of Banan District, Beibei District, Bishan District, Fengdu County, Fengjie County, Jiangbei District, Nan'an District, Nanchuan District, Pengshui County, Qianjiang District, Rongchang District, Shizhu County, Tongnan District, Wanzhou District, Yongchuan District, Yuzhong District, Changshou District, and Zhongxian County were −0.139, 0.228, 0.587, 0.042, −3.365, 0.587, 0.597, 0.587, 0.587, 0.189, −1.127, −0.201, −0.181, 0.587, 0.416, 0.587, 0.587, −0.098, and 0.043, respectively. The comprehensive evaluation values (P50) of the central urban area, the new downtown urban area, the southeastern area, and the northeastern area of Chongqing were 0.587, 0.587, −0.181, and 0.043, respectively. Conclusion The hygienic status of water in public swimming places in Chongqing is above average in China, but there are still potential health problems in turbidity and bacterial pollution in the southeastern area and Fengjie County of Chongqing.