In 2013, the World Health Organization concluded that outdoor air pollution is carcinogen to humans.
Lets look at the research.
Lamichhane and colleagues investigated the association between long-term exposure to ambient air pollution and lung cancer incidence in Koreans. They concluded that This study provides evidence that PM10 (particle matter) and NO2 contribute to lung cancer incidence in Korea.
Lamichhane, D. K., Kim, H. C., Choi, C. M., Shin, M. H., Shim, Y. M., Leem, J. H., … Park, S. M. (2017). Lung Cancer Risk and Residential Exposure to Air Pollution: A Korean Population-Based Case-Control Study. Yonsei medical journal, 58(6), 1111–1118. doi:10.3349/ymj.2017.58.6.1111
According to a meta -analysis titled Long-Term Exposure to Air Pollutants and Cancer Mortality: A Meta-Analysis of Cohort Studies, it was concluded that “exposure to the main air pollutants is associated with increased mortality from all cancers.”
Kim, H. B., Shim, J. Y., Park, B., & Lee, Y. J. (2018). Long-Term Exposure to Air Pollutants and Cancer Mortality: A Meta-Analysis of Cohort Studies. International journal of environmental research and public health, 15(11), 2608. doi:10.3390/ijerph15112608
Grant wrote an article titled, Air Pollution in Relation to U.S. Cancer Mortality Rates: An Ecological Study; Likely Role of Carbonaceous Aerosols and Polycyclic Aromatic Hydrocarbons. He stated “important factor for cancer is air pollution, primarily from fossil fuel combustion. Particulates were identified as the pollutant most highly correlated with mortality rates from air pollution in the U.S.”
Grant WB. Air pollution in relation to U.S. cancer mortality rates: an ecological study; likely role of carbonaceous aerosols and polycyclic aromatic hydrocarbons. Anticancer Res. 2009;29(9):3537–3545. Chronic exposure to traffic-related air pollution may constitute an environmental risk factor for cancer post-myocardial infarction.
G. Cohen, I. Levy, Yuval, J.D. Kark, N. Levin, D.M. Broday, D.M. Steinberg, Y. GerberLong-term exposure to traffic-related air pollution and cancer among survivors of myocardial infarction: a 20-year follow-up study Eur. J. Prev. Cardiol., 24 (2017), pp. 92-102