Results of a study hint that exposure to PCBs (polychlorinated biphenyls) increases the risk of the development of non-Hodgkin’s lymphoma (NHL), a blood cancer involving the lymph nodes.

The incidence of NHL has risen over the past several decades but the reasons for this are unclear, study investigators explain in the July issue of the journal Epidemiology.

In a population-based, case-control study, they examined the association between NHL risk and exposure to organochlorine compounds using concentrations in carpet dust as an exposure indicator. They collected carpet dust samples from the homes of 603 NHL patients and 443 controls. The subjects had owned most of their carpets for at least 5 years.

Dr. Joanne S. Colt, of the National Institutes of Health, Rockville, Maryland, and colleagues found that the risk of developing NHL was 50 percent higher if any of the PCB compounds was detected.

The greatest effects were observed for one particular PCB compound (PCB 180), “for which NHL risk increased steadily as dust residues of the compound increased,” Colt said.

The study also provides some evidence that DDE, a breakdown product of DDT, another organochlorine compound, contributes to the increased risk of NHL.

“PCBs and DDT were banned in the United States in the 1970s,” Colt said. “However, exposure to these compounds was once widespread and they continue to be ubiquitous environmental pollutants,” she added. “If the association observed in our study is real, these compounds could have contributed to the risk of NHL observed over the past several decades.”

The authors do not believe that contaminated carpet dust is a major route of exposure to these compounds. “However,” she added, “because these chemicals persist in carpets for many years, their presence in carpet dust today could be indicative of exposures that occurred many years ago.”

SOURCE: Epidemiology July 2005.