Air pollution is a well-established cause of morbidity and mortality. It largely comes from manmade sources such as particulate matter that arises from burning fossil fuels, which is a major contributor of greenhouse gas emissions.
Dr. Joan Schiller
leading to respiratory and cardiovascular diseases and even death because of cardiopulmonary conditions and lung cancer.
The 2015 Global Burden of Disease study lists air pollution as the fourth highest–ranking global mortality risk factor. The World Health Organization estimated that 4.2 million deaths were caused by outdoor air pollution in 2016, and another 2.3 million from indoor air pollution.
Not all oncologists believe that air pollution is a cancer problem, but air pollution and particulate matters are carcinogens and in fact, they have been deemed level 1 carcinogens by the International Association of Research on Cancer.
The research on the link between air pollution, PM2.5 and lung cancer is robust. Numerous epidemiological studies have shown that people living in highly polluted areas are more likely to die of lung cancer than those who do not. For example, Turner and colleagues in CA: A Cancer Journal for Clinicians performed a Cox proportional hazard regression model adjusting for numerous variables – smoking, passive smoking, occupational exposures (asbestos, coal dust, diesel engine exhaust, etc.), an occupational “dirtiness” index, radon exposure, among others – and found a dose-response relationship between PM2.5 concentration and lung cancer mortality (each 10-mg/m increase in PM2.5 concentrations was associated with a 15%-27% increase in lung cancer mortality).
A similar analysis by Coleman and colleagues in Cancer Causes and Control found lung cancer mortality was adversely associated with increases in PM2.5 not only in the overall population that was studied, but also in a never-smoker cohort. A study reported in Environmental Health Perspectives also showed that exposure to air pollution increases the incidence and mortality from lung cancer, with lung cancer risk associated with PM2.5 exposure being greatest for former smokers (hazard ratio, 1.44; 95% CI, 1.04-2.01), followed by never-smokers (HR, 1.18; 95% CI, 1.00-1.39), and then current smokers (HR, 1.06; 95% CI, 0.97-1.15).
A 2020 study reported in Thorax that patients with COPD who have never smoked were more likely to get lung cancer, compared with never-smokers without COPD (HR, 2.67, 95% CI, 2.09-3.40). Other studies (The Lancet Oncology and The Lancet) confirm these findings. A meta-analysis published in Environmental Research of a large number of cohort studies over the past 25 years reported that the estimated HR, adjusted for age, sex, and smoking status, was 1.13 (95% CI, 1.07-1.20) per 10 mcg/m elevation in PM2.5.
Air pollution also affects patients who already have lung cancer. Air pollution exposures after the diagnosis of lung cancer shortens survival. For example, a 2016 study published in the journal Thorax found the median survival for patients with early-stage lung cancer at diagnosis was 2.4 years for those with high PM2.5 exposure (≥ 16 mcg/m3) and 5.7 years for those with low PM2.5 exposure (< 10 mcg/m3).