A new study shows that an alarming trend is emerging—incidences of lung cancer among non-smokers are on the rise, and pollution in the air could be a major reason. The study published on World Cancer Day in The Lancet Respiratory Medicine established that environmental factors may play a more important role in cases of lung cancer than has previously been assumed.

The International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) researchers analyzed data from the Global Cancer Observatory 2022 dataset. There are four subtypes of lung cancer that were under focus: adenocarcinoma, squamous cell carcinoma, small-cell carcinoma, and large-cell carcinoma.

They found that adenocarcinoma, a cancer that originates in the glands that produce mucus and digestive fluids, is now the dominant subtype of lung cancer in both men and women. In 2022, adenocarcinoma made up 53-70% of lung cancer cases among non-smokers globally. Unlike other forms of lung cancer, adenocarcinoma is only weakly associated with cigarette smoking, the authors explained.

How smoking habits and pollution are changing lung cancer trends

“As smoking prevalence continues to decline in many countries worldwide, the proportion of lung cancer in people who have never smoked has increased,” the study noted.

Freddie Bray, lead author and head of IARC's cancer surveillance branch, pointed out that changing smoking habits and rising exposure to air pollution are key factors behind this shift in lung cancer cases.

The deadliest form of cancer is lung cancer, which continues to be the leading cause of cancer-related deaths globally. In fact, this study shows that the disease also affects non-smokers. Researchers estimated that the fifth leading cause of cancer-related deaths globally has now become lung cancer in non-smokers, particularly affecting women and Asian populations.

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The impact of air pollution on lung cancer

In 2022 alone, there were an estimated 908,630 new lung cancer cases among women worldwide, with 541,971 (nearly 60%) being adenocarcinoma cases. The study further estimated that 80,378 of these cases were linked to ambient particulate matter (PM) pollution.

“The diverging trends by sex in recent generations offer insights to cancer prevention specialists and policy-makers seeking to develop and implement tobacco and air pollution control strategies tailored to high-risk populations,” Bray said.

As of 2019, more than half of the world's population was estimated to live in places that fail to meet WHO's air quality standards.

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