PCBs (polychlorinated biphenyls), the compounds found in plastics, insulation materials and flame retardants, may be responsible for the increase in the incidence of non Hodgkin's lymphoma.
Researchers have discovered high concentrations of PCBs in the blood of non Hodgkin's patients. PCB levels were 9 per cent higher than among people who did not have the disease.
They based their findings on 74 patients whose blood serum was matched against 147 controls in a study that began in 1974 in Washington County, Maryland.
Although PCBs have long been recognized as carcinogenic, scientists have not been able to draw a distinct link to a specific type of cancer before.
The discovery, made by researchers at the National Cancer Institute in Bethesda, Maryland, was accidental, as they were looking for a link between the cancer and the pesticide DDT, something they were unable to establish.
They warn that their conclusion is hypothetical and still needs further work, but it could cast light on a cancer that has increased manyfold in the US and the UK since the 1940s and whose cause has remained a mystery (Lancet, 1997; 350: 240-4).