BC Cancer Agency study largest of its kind to date

A study by BC Cancer Agency scientists provides new evidence that environmental contaminants – organochlorine pesticides and polychlorinated biphenyls (PCBs) – increase the risk of non-Hodgkin lymphoma (NHL). The study, the largest of its kind to date, will be published later this week in the International Journal of Cancer.

“We know that the incidence of non-Hodgkin lymphoma has been steadily rising for the past 30 years worldwide, but there hasn’t been clear evidence to explain the increase,” says Dr. John Spinelli, lead author and a senior scientist at the BC Cancer Agency, an agency of the Provincial Health Services Authority. “Our study helps to provide answers to this puzzle by showing a strong link between these specific environmental contaminants and this particular type of cancer.”

“We are also seeing incidence rates for NHL leveling off in recent years, and this provides further evidence that these contaminants are important because many of these chemicals are no longer in use or are being used at reduced and highly controlled levels,” adds Dr. Spinelli.

Dr. Spinelli and his team collected blood samples from close to 900 British Columbians – half with NHL and the other half without – and tested the samples for exposure to organochlorine pesticides and PCBs. Study participants also answered a questionnaire about demographic characteristics, sunlight exposure, medical history, and other potential risk factors.

Participants with NHL showed much higher levels of environmental contaminants than the control group. Individuals who had the highest total exposure to PCB showed twice the risk of NHL compared to those with the lowest exposure. The strongest association was observed for oxychlordane (a by-product of the pesticide chlordane). Individuals with the highest levels of oxychlordane had 2.7 times the risk of NHL compared to those with the lowest exposure.

“Looking strictly at environmental factors won’t provide the full picture,” said Dr. Spinelli. “Our next step is to identify genetic factors that make individuals more susceptible to these environmental contaminants. In this way, we may be able to determine the mechanism by which contaminants increase the risk for lymphoma, and this knowledge may help to identify environmental risk factors earlier.”

Exposure to organochlorine residuals can occur through the diet. Today in Canada, PCBs are only allowed to be used as insulating fluid in existing electrical equipment. In the past they have been used as flame retardants, hydraulic fluid, lubricating and cutting oil, and additives in pesticides, paints, and carbonless paper. Most organochlorine pesticides have been banned in Canada, but many are still in use in other parts of the world.

Environmental data contained in Ministry of Environment State of the Environment reports shows that more stringent regulation reduced the quantity of PCBs in use in Canada by 54% between 1992 and 2003. In British Columbia, PCB and organochlorine pesticide (i.e. chlordane) content in Great Blue Heron eggs has shown a similar reduction of up to 80% in eggs collected between 1977 and 1999.

“This study is very important because it adds to our understanding of how exposure to chemicals that have become very common in our environment increases our risk of developing lymphoma,” says Dr. Joseph Connors, Chair of the Lymphoma Tumour Group at the BC Cancer Agency and co-investigator on the study.

The study is funded by the Canadian Cancer Society through the National Cancer Institute of Canada, and the Canadian Institutes of Health Research. One of the authors, Carmen Ng, was supported by the Michael Smith Foundation for Health Research. The BC Cancer Foundation provides core funding for research at the BC Cancer Agency.

In 2007, an estimated 966 British Columbians will be diagnosed with non-Hodgkin lymphoma and 383 will die of it. One in 54 females and one in 44 males is expected to develop non-Hodgkin lymphoma during their lifetime. One in 119 females and one in 92 males is expected to die of Non-Hodgkin lymphoma.

For more information or to schedule an interview, please contact:

Jinny Wu
Communications Specialist
BC Cancer Agency
Tel: 604.877.6272
Toll-free: 1.800.663.3333, ex 6272
jwu2@bccancer.bc.ca