Toxic and transforming effects of benzo(a)pyrene on mammalian cells. Difficulties arising during research for an equivalence with the effects of radiation

As a first step towards a quantitative comparison of the effects of benzo(a)pyrene and of X-irradiation, study dealt with the toxic effect of chemical and physical agents on mammalian cells. On hamster embryo cells in culture, the quantities of chemicals or pollutants and the doses of X-irradiation which will kill the same percentage of cells, were compared. Secondary hamster embryo cells have been exposed for 24 hours to different amounts of benzo(a)pyrene or to X rays (250 kV; Al filtre 2). The results of this first experiments, show for, example, that for a survival of 20% of the cells, measured six days after the treatment, to a dose of 585 rads corresponds 1 μg of benzo(a)pyrene. The quantification of carcinogenic effects in this in vitro system should take into account: the quantity of the compound to which the cells have been exposed and the duration of this treatment; the latency of appearance of malignant transformation; the minimal number of cells required to induce tumors through grafting. To compare the transforming effect of chemicals and the one of radiation, information on the transforming effect of radiation, must be obtained