Effect of video display terminal irradiation on urethane-induced lung carcinogenesis in mice

Female Swiss-derived SHR mice were exposed intraperitoneally to 4 injections of 1% urethane at the Ist, 8th, 54th and 61st days of the experiment (a single dose was 20 mg per mouse). Groups of mice starting from the Ist day were also exposed 5 days per week to 1 hour irradiation of video display terminal (VDT) or VDT+ screen filter (SF). The distance from VDT screen and bottom of animal cage was 38 cm. The experiment was finalized in 1 year. Longterm exposure of urethane-treated mice to both VDT or VDT+SF was followed by slight decrease in survival time of lung tumor-bearing animals. The tendency to increase of the incidence of lung tumors and the number of lung tumor per mouse was observed in mice exposed to urethane + VDT as compared to those exposed to urethane alone. The incidence of lung tumors and lung tumor multiplicity were significantly decreased in mice treated with urethan and VDT+SF in comparison to mice exposed to urethane + VDT. Thus, a slight promoting effect of VDT-induced irradiation on lung tumorigenesis was observed induced by urethane in mice, and SF alleviated this effect. The dose of urethane in these experiments was rather high to show more clearly the effect of VDT irradiation on lung carcinogenesis.