国际公共卫生与安全杂志

Variation of Inorganic Compounds in Home Bath Water

Abstract

Jun Kobayashi, Keiichi Ikeda and Hideo Sugiyama

Bath water is heated to warm the body, and in Japan it is used to remove cleaning agents from the skin before entering the bathtub. Usually this water does not enter the body, but there have been cases where people have caught infectious diseasesthrough inhalation of aerosols. In this study, we examined the change in hygiene and chemical composition of the bathtub water in various conditions as a model of circulating bath. To investigate the potential for bacterial growth in home bath water in Japan, changes in the concentrations of metal and non-metal inorganic compounds were studied as the number of days the water was re-used. With re-use of bath water within 1 week, the concentrations of most of the compounds increased, but the phosphorus decreased. Increasing concentrations could be attributed to sweat secreted from skin of the bather, compounds eluted from the water heater, as the bath water was re-heated, and addition of bath salts. Consumption of inorganic compounds by bacteria and precipitation of metal hydroxides could be thought to the decreasing concentrations. Common bacteria and coliform bacteria were also measured simultaneously, and only the coliform bacteria increased in the water on the second day the water was used for bathing. It seems bacteria probably grew in the pipes between the water heater and the bathtub.