January 15 – 21 is National Non-Smoking Week in Canada and while quitting smoking can lower your risk of developing lung cancer, statistics around the world are showing an increase in lung cancer diagnoses in people who are non-smokers. In B.C., approximately 33 per cent of lung cancer patients presenting to BC Cancer – Vancouver have never used tobacco products. New research at BC Cancer suggests lifetime exposure to air pollution, specifically a particle called PM2.5, could be causing an increase in lung cancer diagnoses.
“There is an urgent need to create a risk prediction tool to identify the people who don’t use tobacco, yet are at increased risk of developing lung cancer,” says Dr. Renelle Myers, principal investigator at the Leung Breathomics Lab and lead for the Smoking Cessation Program at BC Cancer. “Furthering our understanding, an individual’s PM2.5 risk could help us to expand screening for lung cancer which can identify tumours at an early, curable stage for more people.”
In 2014, the World Health Organization (WHO) classified a component of air pollution called PM2.5, which is particulate matter less than 2.5 microns per cubic meter as a cancer-causing agent.
To establish exposure to PM2.5, Dr. Myers and her team took detailed residential histories of 236 lung cancer patients at BC Cancer, recording where they lived from birth to cancer diagnosis. What they found was that over 80 per cent had lived outside of Canada the majority of their life and 71 per cent of those lived in Asian countries like China or Taiwan. They then used the residential histories and compared that with satellite data going as far back as 1996 to find each individual’s actual PM2.5 exposure over 3 years and over 20 years. This research was recently presented during the International Association for the Study of Lung Cancers.
“When we looked at the 20-year exposure we saw at least 20 per cent of lung cancer patients who have never smoked had an annual average air pollution exposure of over 10 micrograms of PM2.5 per meter squared,” says Dr. Myers. WHO recommends an annual mean PM 2.5 exposure of less than 5 micrograms of PM2.5 per meter squared.
People living in B.C. may also be exposed to what WHO considers dangerously high levels of PM2.5, especially during wildfire season. To help reduce exposure, the BC Centre of Disease Control puts out information on daily PM2.5 levels. Dr. Myers says when the sky is smoky, it’s important British Columbians follow the recommendations based on PM 2.5 levels, including limiting outdoor exercise and closing windows.
“Just like we look at the UV Index for sun protection because we know UV exposure can cause skin cancer, we need to start looking at the PM2.5 levels when it’s smoky outside and protect yourself.”
As Dr. Myers and her team get closer to figuring out how – biologically – air pollution causes cancer, they are also looking ahead to how their findings can help inform climate policies and incorporate lifetime PM2.5 exposure as a risk factor for screening.
“Lung cancer used to be viewed as a tobacco users disease but it’s not. Anyone with lungs can get lung cancer and we all have to look harder at our lung health and our environmental health. As a community, a nation and globally, we have to really start paying close attention to our environmental health.”