A nested case-control study of non-Hodgkin lymphoma and serum organochlorine residues

Background The steady worldwide increase in the incidence of non-Hodgkin lymphoma during the past few decades remains mostly unexplained. Several studies suggest that there may be an association between the agricultural use of the organochlorine 1,1,1-trichloro-2,2′bis(p-chlorophenyl)ethane (DDT) and increased risk of non-Hodgkin lymphoma. We have investigated the association between risk of non-Hodgkin lymphoma and body burden of selected organochlorines in the general population in a nested case-control study. Methods We measured prediagnostic serum concentrations of DDT, its metabolites, and other organochlorines, including polychlorinated biphenyls (PCBs), in 74 cases of non-Hodgkin lymphoma and 147 matched controls identified from a prospective cohort of 25 802 adults, established in 1974 in Washington County, Maryland, USA. We report results for total lipid-corrected serum concentrations of DDT and total PCBs. Findings There was a strong dose-response relation between quartiles of total lipid-corrected serum PCB concentrations and risk of non-Hodgkin lymphoma overall (odds ratios by quartile: 1·0; 1·3 [95% CI 0·5–3·3]; 2·8 [1·1–7·6]); and 4·5 [1·7–12·0]; p for trend=0·0008) and separately in men and in women. There was also evidence suggesting that seropositivity for the Epstein-Barr virus early antigen potentiated the effects of serum PCBs. By contrast, total lipid-corrected serum concentrations of DDT were not associated with risk of non-Hodgkin lymphoma. Interpretation These results should be regarded as hypothesis-generating. Before causal inferences can be made about exposure to PCBs and increased risk of non-Hodgkin lymphoma, our findings require replication and the biological plausibility of the association needs further investigation.