A recent study published in The Lancet Respiratory Medicine revealed an increase in lung cancer cases among non-smokers, linking this rise to air pollution exposure. The study, released on World Cancer Day, reported the growing prevalence of adenocarcinoma, a subtype of lung cancer that is becoming increasingly common among individuals who have never smoked.
According to the study, approximately 200,000 cases of adenocarcinoma worldwide in 2022 were associated with exposure to air pollution, indicating a causal relationship between air pollution and adenocarcinoma risk. Researchers from the International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) analyzed data from the Global Cancer Observatory 2022, examining lung cancer cases across four subtypes: adenocarcinoma, squamous cell carcinoma, small-cell carcinoma, and large-cell carcinoma.
"If the global proportion of adenocarcinomas attributed to ambient air pollution increases, it depends on the relative success of future strategies to reduce tobacco consumption and air pollution globally," said Dr. Freddie Bray, head of the Cancer Surveillance Branch at IARC and principal author of the study, according to The Sun.
The study found that adenocarcinoma has become the predominant subtype of lung cancer among non-smokers, accounting for 53% to 70% of cases in this group. This type of cancer starts in the glands that produce mucus-like fluids and has become the most common form of lung cancer identified among both genders. In 2022, adenocarcinoma accounted for 45.6% of new lung cancer cases among men (717,211 cases) and 59.7% among women (541,971 cases).
East Asia records the highest rate of adenocarcinoma, with 27.12 cases per 100,000 men and 19.04 per 100,000 women, particularly in China, where urban air pollution levels are exceptionally high. Researchers noted that exposure to the burning of solid fuels in households for heating and cooking could be a factor in rising lung cancer cases among Chinese women who have never smoked, The Independent reported.
"Lung cancer in those who never smoke is also appearing almost exclusively as adenocarcinoma, which has become the most dominant of the four main subtypes of the disease in both males and females globally," stated the IARC, Adevarul reported. The World Health Organization (WHO) announced an increase in the number of lung cancer cases among people who have never smoked, with evidence suggesting that the percentage of diagnoses among this group is rising as smoking prevalence declines in many countries.
While lung cancer incidence rates in men have generally decreased over the past 40 years, rates in women are increasing, with the gap between lung cancer incidence in men and women narrowing. In 2022, approximately 1.6 million men and 900,000 women were diagnosed with lung cancer, indicating a reduction in the difference between the number of cases among men and women.
"Changes in smoking patterns and exposure to air pollution are among the main determinants of the changing risk profile of lung cancer by subtype that we see today," said Bray, as reported by Deutsche Welle. He emphasized that the results provide clues on how to better prevent the disease globally.
Despite the overall decrease in smoking rates worldwide, lung cancer remains the leading cause of cancer mortality globally, accounting for most cancer-related deaths. In 2022, approximately 2.5 million new cases of lung cancer were reported globally, making it the most common form of the disease.
Experts attribute the differences in lung cancer incidence rates between men and women to historical smoking prevalence, noting that smoking rates peaked much earlier in men than in women. The researchers found that from 2020 to 2022, adenocarcinoma was responsible for six out of ten lung cancer cases in both men and women.
As air pollution levels remain high in many regions, especially in urban areas of East Asia and Southeast Asia, a large portion of the global population continues to be exposed to pollutants that increase the risk of lung cancer. Globally, it is estimated that fine particulate pollution caused 114,486 cases of adenocarcinoma in men and 80,378 in women.
Health experts urge individuals to be aware of the symptoms of lung cancer, which often include a persistent or worsening cough, chest pain, shortness of breath, unexplained weight loss, and constant fatigue. Early detection is critical, as lung cancer is often diagnosed in advanced stages when treatment options are limited. A persistent cough that does not improve or worsens over time may be an early symptom of lung cancer.
"With the decline in the prevalence of smoking, the percentage of lung cancer diagnosed among those who have never smoked tends to increase," stated Bray. He emphasized the need for comprehensive strategies to reduce air pollution and address other environmental risk factors to prevent further increases in lung cancer cases among non-smokers.
This article was written in collaboration with generative AI company Alchemiq