Alberta Cancer Foundation

Understanding Lung Cancer In People Who Don’t Smoke

By: Jennifer Friesen

Illustration by Sheila Toderian

While the vast majority of lung cancers are associated with smoking, 20 per cent of lung cancers in Canada are not. According to Dr. Alain Tremblay, respiratory medicine specialist at Foothills Medical Centre, professor of medicine at the Cumming School of Medicine and medical lead of the new Alberta Lung Cancer Screening Program, if non-smoking lung cancer was its own designation, it would be one of the top five cancers in Canada. Here, he explains the risks of developing lung cancer for people who have never smoked.

Q: Do you encounter many people who believe lung cancer is solely caused by smoking?

Yes, most of us associate lung cancer with smoking. No one deserves to get lung cancer, whether they use cigarettes or not. A substantial number of the lung cancers we see are people who have smoked less than 100 cigarettes in their lives. Of all the lung cancer patients we diagnose in our clinic right now, more than 50 per cent are not currently smoking, with many having already quit in the past.

Q: What are the different kinds of lung cancer, and who is most at risk?

There are 50 different types of lung cancer now, and it’s all based on the molecular signatures of the cancers and the mutations. One of the first mutations that was actionable, meaning there was a treatment for it, was the EGFR-mutant lung cancer. It became clear very early on that there were four types of people who got these mutations much more commonly: women, people who didn’t smoke, people of Asian heritage and people with the subtype of pathological lung cancer called adenocarcinoma.

Q: What factors, outside of smoking, might contribute to the development of lung cancer?

Second-hand smoke is a big one. Approximately two to three per cent of all lung cancers are found to be second-hand smoke-related. The second most important external cause of lung cancer is radon gas. Radon gas is a naturally occurring radioactive gas that comes out of the soil. If it comes out in the environment, it gets diluted quickly, so it’s not of much consequence, but when it gets into your basement, the radon can accumulate. It also seems to be synergistic with smoking. Many factors for lung cancer are like that — it’s not always one thing; it’s a combination of things. Another big one is air pollution, especially if you live in big cities or Western Canada, considering all the forest fires that we’ve had over the last few years. There’s also a long list of occupational carcinogens people are exposed to at work, with asbestos being a major factor in Alberta.

Q: What are some genetic factors that contribute to lung cancer?

The simplest factor is family history. For a similar exposure to tobacco, if someone has a first-degree relative with lung cancer, a person would be at higher risk than someone else with the same exposure, but no family history. We also know certain populations have higher risk for lung cancer. In particular, the baseline risk of lung cancer in non-smokers is much higher in Asian populations than it is in Canadian Caucasian populations.

Q: What can people do to avoid added risk?

The good thing about radon is that you can do something about it. It’s actionable, and there’s a lot of work being done to get people to test their homes and do some mitigation. You can get a radon test kit for $50 or $60 and make sure you and your family are not exposed to high levels. For asbestos, anyone involved in construction installation, renovating a building or demolishing a building built before the late ‘70s, you have to take precautions.

For more information on radon testing kits and mitigation measures, visit