Engel LS, et al. - In this case-control study nested within two prospective cohorts, researchers assessed links between organochlorine insecticide concentrations and cancer registry-identified primary liver cancer. Participants were 136 cases and 408 matched controls from the Kaiser Permanente Northern California Multiphasic Health Checkup (MHC) cohort and 84 cases and 252 matched controls from the population-based Norwegian Janus cohort. They used collected sera to determine concentrations of nine organochlorine insecticides/metabolites and markers of hepatitis B and C. A suggestive exposure-response trend for trans-nonachlor (second and third tertile of analyte ORs=1.63 and 1.95, respectively) and a nonsignificantly elevated risk for the highest tertile of oxychlordane were reported for MHC participants with sera from the 1960s. An apparent trend for p,p'-DDT (second and third tertile ORs=1.70 and 2.14, respectively) was noted among Janus participants with sera from the 1970s. Limited evidence demonstrated the possibility of an increased risk of primary liver cancer in association with exposure to p,p'-DDT and chlordane-related oxychlordane and trans-nonachlor.