These studies have shown that coal emissions with the highest PAH levels have the strongest associations with lung cancer, a finding that is consistent with the PAH-type of mutation spectra found in the tumor protein p53 (TP53) and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) genes of lung tumors from smoky-coal–exposed women (DeMarini et al. 2001). Here, KRAS is linked to lung cancer.