Editor’s Note: For more on air pollution and lung cancer, learn about the biology behind the carcinogenesis of particulate matter in an interview with Dr. Charles Swanton.
After tobacco smoking, fine air pollution particulates—those smaller than a human hair—cause more deaths from lung cancer each year than any other source.1 Unfortunately, despite strong evidence that smoking is but one risk factor, screening efforts remain largely focused on smoking history.
Christine Berg, MD, who is former chief of the early detection research group at the US National Cancer Institute, hopes that changes.
“I have spent a lot of time on lung cancer risks and trying to improve the selection of patients for lung cancer screening to account for exposure to the many risk factors beyond cigarette smoking,” Dr. Berg said during a presentation on air pollution and lung cancer on March 29 at the 2023 European Lung Cancer Congress in Copenhagen.
Changing screening guidelines—and long-held beliefs—requires a better understanding of the epidemiology of lung cancer caused by air pollution from fine particulate matter (PM 2.5), which Dr. Berg has been studying. She reviewed the data from several studies, including one of her own, that illustrate the burden of air pollution and climate change on lung cancer.
“Ambient particulate air pollution is the second leading contributing factor to lung cancer deaths across the world,” she said. “The sources of this air pollution are varied, but it is primarily driven by our power sector use, our transportation, and an increase in the frequency and massiveness of wildfires related to the greenhouse gas emissions that come from sources one and two.”
Dr. Berg shared recent data2 that estimate air pollution causes about 265,000 lung cancer deaths globally each year, which is about 14% of all lung cancer deaths. In the US, 7,420 deaths or about 13% of all lung cancer deaths are attributable to air pollution annually. This includes people who smoke, those who used to smoke, and those who never smoked. This is the total attributable to air pollution, she said.
Dr. Berg then reviewed a meta-analysis3 that looked at 17 studies to estimate the relative risk for lung cancer caused by PM 2.5.
“It showed a relative risk for lung cancer of 1.16 with each 10 microgram per meter cubed increase in exposure,” she said. “Importantly, the risk appears to be linear, so even below a 10 microgram per meter cubed level there is a risk, and there is a higher associated risk from East Asia. The information suggests there may be some genetic underpinnings to this. We need to really delve into the genetic underpinnings of lung cancer to better serve our patients. Air pollution is a risk factor for everyone.”
As an example, she cited a study2 that looked at the hazard ratio of lung cancer in patients who never smoked.
“Some may think 1.2 to 1.4 hazard ratios are pretty small, but when you have air pollution levels as we have across the world, this kind of hazard ratio can translate into many thousands of individuals,” Dr. Berg said. “And again, it is a positive dose response relationship.”
The body of epidemiologic evidence recently led France’s International Agency for Research on Cancer to assess outdoor air pollution as a Class 1 carcinogen like cigarette smoke and diesel engine exhaust. Additionally, the World Health Organization has reviewed the emerging data and in 2021 released a new air quality guideline, which dropped the recommended healthy exposure level of PM 2.5 to 5 micrograms per meter cubed. The US Environmental Protection Agency has also recently reviewed the evidence and proposed lowering the recommended exposure level of PM 2.5 down to 8 micrograms per meter cubed.
“Hopefully we’ll have tighter air quality standards coming soon in the US, which would be very nice,” Dr. Berg said. “…Both smoking and air pollution are important in causing lung cancer. And both need to be eliminated to help prevent lung cancer and save lives.”
- 1. Cohen AJ, Brauer M, Burnett R, et al. Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015 [published correction appears in Lancet. 2017 Jun 17;389(10087):e15] [published correction appears in Lancet. 2018 Apr 21;391(10130):1576]. Lancet. 2017;389(10082):1907-1918. doi:10.1016/S0140-6736(17)30505-6
- 2. Turner MC, Andersen ZJ, Baccarelli A, et al. Outdoor air pollution and cancer: An overview of the current evidence and public health recommendations [published online ahead of print, 2020 Aug 25]. CA Cancer J Clin. 2020;10.3322/caac.21632. doi:10.3322/caac.21632
- 3. Ciabattini M, Rizzello E, Lucaroni F, Palombi L, Boffetta P. Systematic review and meta-analysis of recent high-quality studies on exposure to particulate matter and risk of lung cancer. Environ Res. 2021;196:110440. doi:10.1016/j.envres.2020.110440