Cancer is a complex group of diseases, each with many possible genetic, lifestyle and environmental causes. Chemicals, substances, and occupations are collectively referred to as exposures. Exposures that are known or suspected to cause cancer (carcinogens) are reviewed regularly by the International Agency for Research in Cancer (IARC). This agency follows a systematic process of assessing the world-wide body of research that has been done around an exposure to determine whether it can be officially classified as a known, probable or possible carcinogen.
Complete information about the classification system and the exposure reviews are available on the IARC website. Because this resource is not written for a lay audience, we’ve summarized some key information:
- Currently, there are 113 exposures classified as “known carcinogens”. These are exposures that have been proven, through many studies, to cause cancer in humans. Many of these substances have been banned in Canada, but others remain all around us, such as tobacco, alcohol, viruses, and ultraviolet radiation (sunlight). Polychlorinated biphenyls (PCB) were recently added to this list, in part due to research conducted in British Columbia.
- Exposures are classified as “probable carcinogens” when they have been shown to cause cancer in animals, but the evidence is less clear for humans. A recently-added example of a probable carcinogen is long-term shift work, which chronically disrupts the body’s normal sleep-wake cycles.
- Exposures that are termed “possible carcinogens” are those where currently there is only limited or inconsistent evidence in humans and insufficient evidence in animals. Much more research needs to be done to get a definitive answer. These include radiofrequency electro-magnetic fields (such as from mobile phones).
There is still a lot we don’t know about the causes of cancer. Plus, there are new chemicals and exposures being introduced into the environment every year. Long-term cohorts like the BC Generations Project provide our best chance to clarify whether current exposures are cancer causing. They also allow us to evaluate in the fastest possible way whether new exposures may be putting our health at risk.
I have spoken to some of you when I first completed my questionnaire due to the area I live in. No one seemed at all interested, however I told you all that several people in our neighbourhood, which is small, have had cancer — in fact almost 50 percent because of what I believe is due to agriculture sprays. When I spoke with one of the leading researchers, she was a little short and said we will know all that because of your postal code. Sure hope you are working on that — it is signifcantly important.
Sharon Leveque
what studies are being done regarding sugar. I read that sugar feeds cancer. follow up because we as a society eat far more of what the food and drug business doesn’t tell us which keeps us sick. regards
This is an excellent question. The evidence is clear that sugar has been a major contributor to the rise in obesity in Canada and other Western countries. The evidence is also pointing to sugar as a major risk factor for both cancer and cardiovascular disease. The evidence is still unclear whether it is the sugar itself, or the insulin produced by the body to digest the sugar that promotes the growth of cancer, but regardless, reducing sugar intake is one of the things we can do right away to lead to better health.
The regional cohorts of the Canadian Partnership for Tomorrow are planning a harmonized questionnaire in order to be able to collect information on each participant’s diet. Measuring individual sugar intake (other than consumption of sugar sweetened beverages) is very difficult due to the ubiquitous nature of sugar in the food we eat. Dr. Paula Robson, the Scientific Director of the Alberta Tomorrow Project is taking the lead on developing the questionnaire. We want to be able to capture as much information on sugar and other risk factors as possible, and to collect the information in a valid and reliable manner.
The environmental questionnaire which will ask about each participant’s residential and occupational history will be the first questionnaire given to BC Generations participants. After that, other questionnaires to capture information on mental health, physical activity and diet will follow. Thank you again for participating in this important Project.