Polychlorinated biphenyls and non-Hodgkin's lymphoma: a case-control study in Northern Italy.

BACKGROUND: Polychlorinated biphenyls (PCBs) have been hypothesized to increase the risk of non-Hodgkin lymphoma (NHL), although conclusive evidence is still lacking. High levels of PCBs were found in soil in some areas close to a PCB-producing factory in Brescia, North Italy. We conducted a population-based case-control study among residents of the town to investigate the possible association between PCB pollution and NHL in this area. METHODS: We included both incident and deceased NHL cases, and a random sample of the town residents as controls, frequency matched to cases as regards age and gender. Exposure to PCBs was estimated on the basis of the lifetime residential history of cases and controls in four different areas of the town-A, B and C (polluted areas) and D (control area). RESULTS: A total of 495 cases (287 incident cases) and 1467 controls were enrolled. Positive associations were found between NHL and having resided for at least 10 years in the area A, the most polluted area (odds ratio, OR=1.8; p=0.02) and for having resided in any of the polluted areas considered together (A+B+C) (OR=1.4; p=0.08). However, no associations were evident for having resided 20 years or longer in the polluted areas or when analyzing the association with each subject's main residence in his/her lifetime. CONCLUSION: This study provides some evidence for an association between PCB exposure and NHL, though results should be considered with caution in the absence of individual biological measures of exposure.