The importance of the AHR to human health is demonstrated in part by epidemiological studies based on the population in Seveso, Italy, that was accidentally exposed to the prototypical AHR agonist 2,3,7,8-tetra-​chlorodibenzo-p-dioxin (TCDD), where the risk for lymphatic and hematological cancers was found to be slightly elevated in adults (Consonni et al. 2008; Pesatori et al. 2009). Here, AHR is linked to hematopoietic and lymphoid cell neoplasm.