UDS-test with freon 11 (R-11).

Trichlorofluoromethane, in concentrations of 80, 400, 2 000, 10 000 and 50 000 ppm, was administered to rats of both sexes (Sprague Dawley) by inhalation exposure.2 000 ppm in air (= 11 200 mg/m(3)) amount to twice the MAK value of 1 000 ppm. At exposure times of 4 hours this corresponds to the MAK value defined for an 8 hour workday.Unscheduled DNA synthesis (UDS) was measured in single-cell suspensions of hepatocytes, pulmonary epithelial cells and lymphocytes of the spleen, respectively.In the pulmonary cells concentrations of 2 000, 10 000 and 50 000 ppm of freon 11 lead to a significantly increased mean silver grain count compared to a negative control group.In spleen and liver cells increasing concentrations of R 11 tend to increase the incorporation of thymidine into the DNA of the cells. These changes of the extent of unscheduled DNA synthesis can, however, not be statistically verified.