Biological safety of neutral-pH hydrogen-enriched electrolyzed water upon mutagenicity, genotoxicity and subchronic oral toxicity

Hydrogen-dissolved water has been suggested to be effective for alleviating the oxidative stress. In the present study, neutral-pH hydrogen-enriched electrolyzed water (NHE-water; dissolved hydrogen: 0.90—1.14 parts per million [ppm]; oxido-reduced potential: —150 ∼ —80 mV), which was prepared with a water-electrolysis apparatus equipped with a non-diaphragm cell and a highly compressed activated-carbon block, was evaluated for the mutagenic and genotoxic potentials, at concentrations up to 100% dose/plate, and for the subchronic toxicity. NHE-water did not induce reverse mutations in Salmonella typhimurium strains TA100, TA1535, TA98 and TA1537, and Escherichia coli strain WP2uvrA, in either the absence or presence of rat liver S9 for exogenous metabolic activation. Similarly, NHE-water did not induce chromosome aberrations in Chinese hamster lung fibroblast cells (CHL/IU), in short-term (6-hour) tests, with or without rat liver S9, or in a continuous treatment (24-hour) test. To evaluate the subchronic toxicity, Crj:CD(SD) specific pathogen free (SPF)-rats were administered with NHE-water at a dose of 20 mL/kg/day for 28 days via intragastric infusion. NHE-water-related toxic changes were not seen in terms of any items such as clinical symptoms, body weight, food consumption, urinalysis, hematology, blood chemistry, necropsy, each organ weight and histopathology. Thus, the no-observable-adverse-effect level (NOAEL) for NHE-water was estimated to be greater than 20 mL/kg/day under the conditions examined, demonstrating the consistency with the expected safety for a human with a body weight of 60 kg to drink the NHE-water up to at least 1.2 L/day.