The Toronto lung cancer case-control study and SYNERGY project

Status: completed


The goal of this project is to examine associations between multiple occupational exposures and smoking within a Toronto-based lung cancer case-control study.

As well, data from this case-control study was contributed to the SYNERGY project. The SYNERGY project is an international study that has pooled data from lung cancer case-control studies performed across Europe and North America. These studies collected information on both occupational risk factors and smoking history. By pooling the data from these studies, a massive database was formed which allows complex interactions between exposures to be analyzed.


Workers are often exposed to multiple carcinogens in their workplace, or over the course of their working life. The effect of these carcinogens in combination is mostly unknown. Studying the interaction between multiple occupational carcinogens is difficult, as the low numbers of people exposed to two or more specific carcinogens results makes statistical analysis challenging. However, understanding the joint effects of occupational carcinogens is important for improving prevention efforts and ensuring appropriate compensation for workers who develop occupational cancer.


For the Toronto study, a questionnaire was given to lung cancer patients and controls to detail their job history, including main tasks and length of employment for all jobs held for at least 12 months. Information on smoking habits was also collected. Therefore, analyses can be done to investigate the risks of occupational exposures while controlling for smoking.

The SYNERGY pooled analyses are being coordinated by the International Agency for Research on Cancer, the Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, and the Institute for Risk Assessment Sciences at Utrecht University. For more information about the SYNERGY project, click here.


It is often difficult to show the effect of exposure to occupational carcinogens due to the huge effect of smoking on the risk of lung cancer, and the small numbers of people exposed to specific combinations of occupational exposures. Pooling data from a number of studies will allow these interactions to be analyzed. Better understanding of the risks of occupational exposures and combinations of exposure could lead to targeted prevention initiatives and better compensation policies for workers with lung cancer.


Analyses of the Toronto database are underway:

  • Initial investigations include wood dust, welding fumes, and pesticide exposure.
  • An analysis of the accuracy of exposure assessment methods was completed, comparing use of a job-exposure matrix to determine asbestos exposure, versus self-reported exposure. Read a summary of the study, or click here to link to the article.

Data from the Toronto study has been contributed to the SYNERGY project. A number of studies from the SYNERGY pooled project have been published:


Paul Demers (Occupational Cancer Research Centre and Cancer Care Ontario) (Co-PI)
John McLaughlin (Samuel Lunenfeld Research Institute) (Co-PI)
Jill MacLeod (Occupational Cancer Research Centre)
Jack Siemiatycki (University of Montreal)
Kurt Straif (IARC)
Hans Kromhout (Utrecht University)
Roel Vermeullen (Utrecht University)
Susan Peters (Utrecht University)
Kate Jardine (Occupational Cancer Research Centre)