Air pollution drives lung cancer surge among non-smokers
An increasing number of lung cancer cases are being diagnosed in people who have never smoked, with air pollution being a significant factor.
What you need to know:
- In Kenya, the impact of air pollution on public health is a pressing concern.
- In Nairobi and other major cities, PM2.5 levels often exceed the WHO's recommended limits, mainly due to vehicle emissions, industrial pollution and open burning of waste.
Lung cancer has traditionally been associated with smoking, but a worrying trend is emerging. An increasing number of cases are being diagnosed in people who have never smoked, with air pollution being a significant factor.
According to a recent study published in The Lancet Respiratory Medicine, lung cancer in non-smokers is now the fifth most common cause of cancer-related deaths worldwide and the leading cause of cancer morbidity. It accounts for nearly one in eight cancers diagnosed worldwide and one in five cancer deaths. The disease ranks first in both incidence and mortality in men and second in women.
The study, conducted by researchers from the International Agency for Research on Cancer (IARC) and the World Health Organization (WHO), highlights air pollution as a major contributor to this rise.
The researchers analysed data from the Global Cancer Observatory 2022 to estimate national lung cancer cases for four subtypes: adenocarcinoma, squamous cell carcinoma, small cell carcinoma and large cell carcinoma. Unlike other lung cancer subtypes, adenocarcinoma typically develops in the outer regions of the lung, making it more susceptible to damage from inhaled pollutants rather than direct exposure to tobacco smoke.
Their findings showed that adenocarcinoma, a subtype that starts in glandular tissue and is only weakly linked to smoking, has become the dominant form of lung cancer in both men and women. Among never-smokers worldwide, adenocarcinoma accounted for 53 to 70 per cent of lung cancer cases in 2022.
According to the Kenya National Cancer Control Strategy 2017-2022, lung cancer accounted for 794 cases and 729 deaths, resulting in a prevalence of 1.75 per 100,000, or a case fatality rate of 92 per cent.
"As smoking prevalence continues to decline in many countries, the proportion of lung cancer cases among people who have never smoked has increased. Changes in smoking patterns and exposure to air pollution are important factors in the changing risk profile of lung cancer by subtype that we see today," said Freddie Bray, head of the Cancer Surveillance Branch at IARC.
The study also found that air pollution is a major factor, with an estimated 80,378 adenocarcinoma cases in women in 2022 associated with particulate matter (PM) pollution. By 2029, almost the entire global population will live in areas that don't meet WHO air quality standards, underscoring the severity of this environmental health crisis.
While smoking remains the leading risk factor for lung cancer, air pollution - particularly fine particulate matter (PM2.5) - has emerged as a significant cause, especially for non-smokers. PM2.5 particles, released from vehicle emissions, industrial activities and biomass burning, are small enough to penetrate deep into the lungs. Prolonged exposure to these pollutants can lead to chronic inflammation, DNA damage and eventually cancer.
In Kenya, the impact of air pollution on public health is a pressing concern. In Nairobi and other major cities, PM2.5 levels often exceed the WHO's recommended limits, mainly due to vehicle emissions, industrial pollution and open burning of waste. In addition, indoor air pollution from biomass fuels such as charcoal and firewood poses a serious health risk, particularly to rural women who rely on these traditional cooking methods.
A report by the National Environmental Management Authority and WHO shows that respiratory diseases, including chronic lung disease, are on the rise in urban areas. The increasing burden of air pollution suggests that cases of lung cancer among non-smokers may be increasing undetected. Women, in particular, are more exposed to both outdoor pollution and indoor smoke from cooking.
"Many Kenyans assume that lung cancer is only a smoker's disease, but we are seeing more patients who have never smoked," said Dr Catherine Ndung’u, a Nairobi-based oncologist. "Air pollution, especially in congested cities, is an important factor that is often overlooked. We need to start looking at pollution control as a cancer prevention strategy, not just an environmental issue".
The link between air pollution and lung disease is well documented, but awareness remains low. "Kenya's rapid urbanisation has come at a price. We have more cars on the roads, more polluting industries and poor waste management. Unfortunately, the health effects of all this pollution are only now becoming apparent," said environmental expert David Mwaura.
"Healthcare systems need to recognise that lung cancer is no longer just a 'smoker's disease'. Improved early detection and research into lung cancer trends among non-smokers in Kenya are essential to ensure that policies reflect changing risk factors. As smoking rates decline globally, environmental hazards such as air pollution are emerging as the next major threat to lung cancer prevention," Dr Ndung’u added.
