Cases of lung cancer in people who've never smoked cigarettes or tobacco are increasing, along with evidence suggesting air pollution plays a role, according to new research. Lung cancer in people who've never smoked is now "estimated to be the fifth leading cause of cancer-related mortality worldwide," occurring most commonly in women and Asian populations, according to the World Health Organization's International Agency for Research on Cancer (IARC), which stresses a startling percentage of these cancers are of one subtype—adenocarcinoma, "a cancer that starts in glands that produce fluids such as mucus and digestive ones," per the Press Trust of India.
Adenocarcinoma is the dominant subtype of lung cancer among men and women. It accounted for 46% of global lung cancer cases among men and 60% among women in 2022, up from 39% and 57%, respectively, in 2020. It also accounts for up to 70% of lung cancer cases among never-smokers, according to the IARC study published in the Lancet Respiratory Medicine journal on Tuesday, which is World Cancer Day. Adenocarcinoma is weakly associated with smoking compared to the other three lung cancer subtypes (squamous cell carcinoma, small-cell carcinoma, and large-cell carcinoma).
Globally, 16% of adenocarcinoma cases diagnosed in men and 15% of cases diagnosed in women in 2022 could be traced to a specific type of air pollution known as particulate matter, a complex mixture of solid and liquid chemical particles, some of which are small enough to be inhaled. "Changes in smoking patterns and exposure to air pollution are among the main determinants of the changing risk profile of lung cancer incidence by subtype that we see today," says lead author Freddie Bray, head of the cancer surveillance branch at IARC, per the Guardian. "Whether the global proportion of adenocarcinomas attributable to ambient air pollution will increase depends on the relative success of future strategies to curtail tobacco use and air pollution worldwide." (More lung cancer stories.)
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