Fig. 6.

Number of revertants in S. typhimurium TA100 upon exposure to a phenanthrene b 1-methylphenanthrene, c 2-methylphenanthrene, d 3-methylphenanthrene and e 9-methylphenanthrene in the absence (black bar) and presence (white bar) of 5% S9-mix. The dotted horizontal line indicates twofold increase that is considered the threshold for concluding on the positive outcome for mutagenicity. Bar represents means and vertical bars are standard deviation of the mean (n = 3). In the absence of the S9 mix, the test doses of 2-methylphenanthrene, 3-methylphenanthrene and 9-methylphenanthrene showed cytotoxicity so no data are presented. The results of at least four analyzable doses that were non-cytotoxic are presented in Table S3 in the supplementary material 1 showing negative results. PC  positive control, 5 µg/plate 2AA with S9-mix and 650 µg/plate MMS without S9-mix. SC  solvent control, DMSO with and without S9-mix