Influence of Residual Chlorine in Tap Water on Protein Carbonylation of Corneocytes and Epidermal Barrier Functions

Abstract

There are some concerns that hypochlorous acid, referred to as residual chlorine hereafter, in tap water causes adverse effects on the human body, especially the skin, due to its strong oxidizing power. However, this detail is still unclear. Therefore, we conducted this study to identify the adverse actions of residual chlorine present in tap water and the effectiveness of purified water focusing on protein carbonylation of corneocytes in the stratum corneum that is correlated with lowered skin moisture functions. An ex vivo examination revealed that the exposure of corneocytes collected by tape-stripping to water containing residual chlorine (residual chlorine water) showed higher protein carbonylation. Additionally, the protein carbonylation promptly progressed after exposure to residual chlorine water. In vivo examination-reproduced situations of the real usage, residual chlorine water increased protein carbonylation of corneocytes. Particularly, the repetition of hand-washing with residual chlorine water increased the value of transepidermal water loss significantly along with higher protein carbonylation of corneocytes. The results suggested that the daily usage of tap water containing residual chlorine could cause protein carbonylation of corneocytes and eventually decrease the epidermal barrier function. The results might indicate a potential action of tap water on people who do not habitually use purified water for body washing. Therefore, this study proposes the possibility that the daily use of purified water instead of tap water could maintain skin health by reducing oxidative damage to corneocytes.