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| |  PCB Exposure May Increase Lymphoma Risk LONDON -- July 25, 1997 -- People who have been exposed to chemicals called polychlorinated biphenyls (PCBs) may have a significantly higher risk of developing non-Hodgkin lymphoma, an often fatal cancer of the lymphatic system, American researchers report in this week’s The Lancet. In the study, the researchers, led by Dr. Nathaniel Rothman of the National Cancer Institute, analysed blood samples that had been collected in 1974 from people living in a rural county of the state of Maryland. Among those who had given blood at that time, the researchers identified 74 who later developed non-Hodgkin lymphoma. They then tested the blood samples that had been collected from these individuals for a number of chemicals including the pesticide DDT and PCBs and compared the concentrations of these compounds in their blood with those of 147 other people who also gave blood samples that year but who had not developed lymphomas. The researchers report that they did not find evidence to suggest that DDT exposure increased the risk of developing lymphoma, but did find a "strong dose-response relation" between higher PCB blood concentrations and an increased risk of developing non-Hodgkin lymphoma. The researchers also found evidence that active infection with the virus that causes mononucleosis, the Epstein-Barr Virus, seems to multiply the effect of raised PCB levels, further increasing the risk of lymphoma. However, the researchers caution that their results do not prove that PCBs cause non-Hodgkin lymphoma. They note that there have been several studies of workers who were exposed to high levels of PCBs that have not found an increased risk of developing the disease. The researchers also note that there may be some other "unrecognised risk factor" associated with raised PCB concentrations, that is responsible for the increased lymphoma risk seen in their study. "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," the researchers conclude. Contact: Dr Nathaniel Rothman, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA; tel +1 301 496 9093.
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