Air pollution causing global increase in lung cancer diagnoses among never-smokers

The World Health Organisation’s cancer agency reports that more non-smokers are being diagnosed with lung cancer, citing air pollution as a significant factor.

Lung cancer in people who have never smoked cigarettes or tobacco is now estimated to be the fifth highest cause of cancer deaths worldwide, according to the International Agency for Research on Cancer (IARC). It says lung cancer in never-smokers is mostly adenocarcinoma, now the most common subtype globally for both men and women.

About 200,000 cases of adenocarcinoma were associated with exposure to air pollution in 2022, according to the IARC study, published in the Lancet Respiratory Medicine journal.

It is particularly prevalent in east Asia, and more specifically China, the study found.

The study’s lead author, head of the IARC’s cancer surveillance branch, Dr Freddie Bray, said the findings underscored the need for urgent monitoring of the changing risk of lung cancer, adding that further studies were also required to identify possible causal factors, such as air pollution, in populations where smoking was not considered the main cause of lung cancer.

“With declines in smoking prevalence – as seen in the UK and US – the proportion of lung cancers diagnosed among those who have never smoked tends to increase,” says Bray. “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.”

Lung cancer is still the leading cause of cancer incidence and mortality worldwide with around 2.5 million people diagnosed with the disease in 2022. But the patterns of incidence by subtype have changed dramatically in recent decades.

Of the four main subtypes of lung cancer (adenocarcinoma, squamous cell carcinoma, small-cell carcinoma and large-cell carcinoma), adenocarcinoma has become the dominant subtype among both men and women, the IARC found.

Adenocarcinoma accounted for 45.6% of global lung cancer cases among men and 59.7% of global lung cancer cases among women in 2022. The respective figures were 39.0% and 57.1% in 2020. It accounts for as much as 70% of lung cancer cases among never-smokers, according to the IARC.

While lung cancer incidence rates for men have generally decreased in most countries during the past 40 years, rates among women have tended to continue to rise. Current trends suggest that while men still make up most lung cancer cases (about 1.6 million in 2022), the gap between males and females is narrowing. Around 900,000 women were diagnosed with lung cancer in 2022.

Cancer experts said the figures reflected historical differences in smoking prevalence, specifically that smoking rates peaked much earlier in men than women. Women should now be as alert to potential lung cancer signs as about checking for lumps in their breasts, they said.

Changes in cigarette manufacturing and smoking patterns in recent decades have influenced the trends in lung cancer incidence by subtype, and there is accumulating evidence of a causal link between air pollution and an increased risk of adenocarcinoma, the IARC said.

How many global lung cancer cases are in never-smokers we don’t know, but evidence suggests it is rising. Scientists are racing to learn more about what else is causing lung cancer apart from smoking.

Bray believes the study provides important insights as to how both lung cancer and the underlying risk factors were evolving, which in turn can help cancer prevention specialists and policymakers develop and implement tobacco and air pollution control strategies tailored to high-risk populations.

• Exposure to toxic air was the explanation for 515 men and 590 women in the UK in 2022 getting adenocarcinoma.
• UK rates of adenocarcinoma cases linked to ambient particulate matter pollution were also higher than in the US and Canada, and four times higher than Finland, which had the lowest rates in northern Europe.
• It is the first time such figures have been compiled by the International Agency for Research on Cancer (IARC).
• Dr Helen Croker, assistant director of research and policy at World Cancer Research Fund, said the figures highlight just how important environmental causes can be when looking at cancer risk.
• Lucy Clark, cancer intelligence manager at Cancer Research UK, said: “While tobacco remains the biggest cause of lung cancer in the UK, this major study shows that air pollution causes hundreds of thousands of lung cancer cases every year across the world.”

Industry and transport are the main causes of air pollution, which means we can all make an impact through changes to our consumption and mobility habits (buy local, use alternative transport options to individual car use, fly less…). And it is to be hoped that major polluters will reduce their impact either voluntarily or through legislation.

This post summarises two separate articles published in The Guardian in February 2025.
Photo by Maxim Tolchinskiy on Unsplash