Formation of stable cyclic estrogen o-quinone DNA adducts: 4-OHEN-dC = N3,3-(N4-dC)-2,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione; 4-OHEN-dA = 1-N6,3-C2-dA-2,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione; 4-OHEN-dG = N1,3-(N2-dG)-1,3-dihydroxy-5,7,9(10)-estratriene-4,17-dione.