a ] py rene ▁( R PF ). ▁Although ▁the ▁concentr ations ▁measured ▁of ▁ben zo [ c ] flu or ene ▁are ▁quite ▁low , ▁when ▁corrected ▁for ▁mut agen icity , ▁ben zo [ c ] flu or ene ▁is ▁the ▁most ▁important ▁PA H ▁of ▁those ▁that ▁were ▁measured ▁in ▁terms ▁of ▁possible ▁health ▁ris ks . ▁ ▁Saf ety ▁ ▁Car cin ogen ity ▁In ▁one ▁study , ▁the ▁Am es ▁test ▁was ▁performed ▁on ▁ben zo [ c ] flu or ene . ▁Two ▁different ▁stra ins ▁were ▁used , ▁T A 1 0 0 ▁and ▁T A 9 8 . ▁One ▁group ▁of ▁each ▁stra in ▁had ▁a ▁rat ▁li ver ▁fraction ▁and ▁one ▁group ▁did ▁not . ▁The ▁difference ▁between ▁the ▁T A 1 0 0 ▁and ▁the ▁T A 9 8 ▁stra in ▁is ▁that ▁the ▁T A 9 8 ▁stra in ▁has ▁a ▁frames h ift ▁mut ation , ▁and ▁the ▁T A 1 0 0 ▁has ▁a ▁base ▁substitution ▁mut ation . ▁When ▁the ▁amount ▁of ▁ben zo [ c ] flu or ene ▁is ▁increased ▁in ▁T A ▁ 1 0 0 ▁ye ast ▁stra in , ▁the ▁amount ▁of ▁revert ants ▁per ▁plate ▁does ▁not ▁increase . ▁Only ▁in ▁the ▁T A 9 8 ▁stra in ▁plate , ▁which ▁contained ▁a ▁fraction ▁of ▁a ▁rat ▁li ver , ▁a ▁higher ▁do se ▁of ▁ben zo [ c ] flu or ene ▁seems ▁to ▁correspond ▁with ▁a ▁larger ▁amount ▁of ▁revert ants