Although many factors are important determinators for the toxicity, the central role of AhR-induced upregulation of CYP1 enzymes in the bioactivation of PAHs is further illustrated by other associations found between tissue specific AhR-dependent aryl hydrocarbon hydroxylase induction/CYP1 isoforms and rates of cancer, mutagenesis, DNA adducts and toxicity of PAHs [130]. Here, AHR is linked to cancer.