A new study has revealed that cases of lung cancer among those who never smoked is on the rise and air pollution could be contributing to the increase. The study was published in The Lancet Respiratory Medicine journal on World Cancer Day on Tuesday.
The team of researchers including those from the International Agency for Research on Cancer (IARC), World Health Organization, analysed data, including those from the Global Cancer Observatory 2022 dataset, to estimate national-level lung cancer cases for four subtypes — adenocarcinoma, squamous cell carcinoma, small- and large-cell carcinoma.
According to the study, adenocarcinoma — a cancer that starts in glands that produce fluids such as mucus and digestive ones — has become the dominant subtype among both men and women.
The study also found that the sub-type of lung cancer was also found to account for 53-70 per cent of lung cancer cases in 2022 among never-smokers around the world. Lung cancer in never-smokers is estimated to be the fifth leading cause of cancer-related mortality worldwide, occurring almost exclusively as adenocarcinoma and most commonly in women and Asian populations. Nearly 200,000 of those diagnosed with adenocarcinoma were associated with exposure to air pollution.
Lung cancer remains the leading cause of cancer-related morbidity worldwide with approximately 2.5 million people diagnosed with it in 2022. Of the estimated 1.5 lakh new cases among men, 717,211 (45.6% of the male lung cancer burden) were adenocarcinoma. Among women, there were an estimated 908,630 new cases of lung cancer worldwide of which 541,971 (59.7% of the female lung cancer burden) were adenocarcinoma, the study found.
At the global level, an estimated 111,486 adenocarcinoma cases among men and 80,378 adenocarcinoma cases among women were attributable to ambient PM pollution. According to the study, adenocarcinoma accounted for 53%–70% of lung cancer cases among never-smokers worldwide, suggesting that the risk of lung cancer linked to air pollution is on the rise, especially in eastern Asia and China.
According to the study authors, compared to the other sub-types of lung cancer, risk of adenocarcinoma is considered to be weakly related with cigarette smoking, the authors explained.
“As smoking prevalence continues to decline in many countries worldwide, the proportion of lung cancer in people who have never smoked has increased,” they wrote.
“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,” lead author Freddie Bray, head of the cancer surveillance branch at IARC, said.
Lung cancer is the leading cause of cancer-related deaths. However, “lung cancer in people who have never smoked is estimated to be the fifth leading cause of cancer-related mortality worldwide, occurring almost exclusively as adenocarcinoma and most commonly in women and Asian populations,” the authors wrote.
“In 2022, we estimated that there were 908 630 new cases of lung cancer worldwide among female individuals, of which 541 971 (59.7 per cent) were adenocarcinoma,” they wrote.
“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, almost everyone in the world is estimated to live in areas not meeting the WHO air quality criteria.
