In addition, exposure of human mammary epithelial cells (HMECs) and breast cancer cell lines to an activated PAH: racemic anti-3,4-dihydroxy-1,2-epoxy-1,2,3,4 tetrahydrobenzo phenanthrene (BPDE), found in active and passive cigarette smoke, exhibited altered cell cycle progression, decreased BRCA-1 expression, an increased a spectrum of p53 mutations [23-26] and neoplastic transformation [5]. Here, BRCA1 is linked to breast cancer.