Is direct-drinking water safe for children? An analysis of direct-drinking water quality and its risk factors in Shanghai elementary and middle schools.

Abstract

Drinking water quality for children should be higher than adults due to both behavioral and physiological factors. Thus, to provide enough, safe, and easily accessible drinking water for children at schools, the Shanghai Municipal Government initiated a direct-drinking water project in 2013. However, there has been no study so far to assess the quality of direct-drinking water or to investigate its risk factors in Shanghai elementary and middle schools. In the present study, we selected direct-drinking water equipment from 183 elementary and middle schools (17% of total) in Shanghai to detect the colony-forming units (CFU), residual chlorine, chemical oxygen demand (COD), and turbidity of water samples, and analyzed the risk factors of its quality using both simple and multiple linear regression analysis. Results showed that the CFU, residual chlorine, COD, and turbidity of direct-drinking water in Shanghai elementary and middle schools ranged from <LOD->300cfu/mL, <LOD-0.670mg/L, 0.090-2.710mg/L, and 0.100-2.050 NTU, respectively. The results of simple linear regression analysis indicated that the CFU of direct-drinking water significantly increased when water temperature was between 25 and 60°C (β=19.862, p = 0.030), but it was decreased at 60-100°C (β=- 16.387, p = 0.046). Additionally, the CFU was higher in elementary schools than middle schools, which was also affected by faucet type and water treatment technology (p=0.006, 0.012 and 0.042, respectively). The residual chlorine in direct-drinking water significantly increased when there was no toilet within 10m (β=0.012, p = 0.045). The COD of direct-drinking water was significantly higher in rural areas and in warm water, compared to urban areas (p = 0.033) and room temperature water (p = 0.000), respectively. The turbidity of direct-drinking water was significantly higher in urban areas and water using UF/MF technology, compared to rural areas (p = 0.030) and RO technology (p = 0.009), respectively. The results of multiple linear regressions analysis drew the same conclusions. In order to improve the quality of direct-drinking water, the equipment should be as far away from toilet as possible and direct-drinking water should be kept at room temperature or heated at high temperature (over 60°C). Furthermore, sanitary standards of direct-drinking water quality and relevant laws and regulations should be established and implemented as soon as possible. Our study demonstrates that it is critical to improve direct-drinking water quality and ensure the safety of drinking water in elementary and middle schools in Shanghai.