Dietary exposure to polychlorinated biphenyls (PCB) and risk of Non-Hodgkin's lymphoma: Evidence from the French E3N prospective cohort

Introduction: Polychlorinated biphenyls (PCB) are persistent and bioaccumulative lipophilic substances, mostly used in the past by industry. Known to be cancerogenic, PCB are suspected to increase Non-Hodgkin's Lymphoma (NHL) risk in the general population mainly due to evidence from cases-controls studies. Since their interdiction in 1987, diet represents the main route of exposure for the general population, nevertheless no study has assessed the relationship between PCB dietary exposure and NHL risk. The aim of this study was to analyze the association between dietary exposures to dioxin like PCB (DL PCB) and non-dioxin like PCB (NDL PCB) and NHL risk in the E3N prospective cohort of French women. Materials and methods: Among 67,879 women included in this study, 457 cases of NHL were confirmed during 21 years of follow-up. Dietary exposure to PCB was estimated combining food consumption data collected in E3N and food contamination data provided by French Agency for Food, Environmental and Occupational Health & Safety (ANSES) in the second French total diet study. Cox regression models, adjusted for potential confounders, were used to estimate hazard ratio (HR) and 95% confidence intervals (CI). Results: Average age at diagnosis was 67 years. The median dietary exposure to DL PCB and NDL PCB was, 18.5 pg TEQ/d and 138,843.2 pg/d, respectively. While no association was found between dietary exposure to DL PCB or NDL PCB and overall NHL risk, analyses by NHL histological subgroups showed a positive association between dietary exposures to DL PCB and Diffuse Large B Cell Lymphoma (OR3vs1 1.90, 95%CI [1.03-3.51], ptrend 0.02). Nevertheless these findings were no longer statistically significant when the models were adjusted for fish and dairy products consumption. In addition, an inverse association was found between dietary exposure to NDL PCB and the risk of follicular lymphoma (OR3vs1 0.46, 95%CI [0.24-0.87], ptrend 0.01). Conclusion: This is the first study to evaluate the association between dietary exposure to DL and NDL PCB and the risk of NHL in a prospective cohort study. Overall, the findings suggest a lack of association between dietary exposure to DL or NDL PCB and NHL risk. Additional studies are needed to reproduce these findings.