Tap Water Shortens the Lifespan of Mice with Prolonged Exposure to Fractionated γ-Radiation

Assessing the role of social factors in the formation of radioresistance in chronic exposure and finding ways to increase it are important for understanding the mechanisms of the damaging effects of radiation and developing practical methods for reducing radiation risk in professionals exposed to ionizing radiation and patients undergoing radiation therapy. In this work, we investigated the ability to influence the lifespan of animals exposed to γ-radiation fractionally for a long time by replacing drinking water from tap water to distilled water. Female ICR mice (CD-1) were exposed to total 60Co γ-radiation weekly in fractions for 33 weeks starting at nine weeks of age. The dose of a single irradiation was 50 mGy, and the average dose rate was 2 mGy/s. The total radiation dose was 1.65 Gy. The control nonirradiated mice and irradiated animals were divided into two groups. The first received tap water, and the second received distilled water throughout the experiment. Nonirradiated animals kept on tap water showed a statistically insignificant (log-rank test, p = 0.483) reduction in average life expectancy compared to mice kept on distilled water. In animals after exposure to 60Co γ-radiation, a statistically significant (p = 0.0013) decrease in life expectancy was noted when kept on tap water and statistically insignificant (p = 0.1511) when kept on distilled water. Tap water and irradiation showed a clear synergy with a combined effect on the body of mice, expressed in a more than threefold decrease in the period of post-radiation shortening of the life expectancy. Distilled water reduced the rate of death of irradiated animals and modified the rate of death of nonirradiated animals. Our data demonstrate that the reduction in the life expectancy of mice kept on tap water caused by long-term fractionated irradiation can be reduced when animals are kept on distilled water.