This article is a commentary on a study published in the journal *Epidemiology* 2000;11(5):487-95. While the causal relationship between air pollution and lung cancer is now well established, the specific source of air pollution responsible for this link is not clearly known. Furthermore, few studies have assessed the effect of long-term exposure to air pollution. The proposed case-control study focuses on men aged 40 to 75 who have primarily resided in Stockholm over the past few decades. Two indicators of air pollution are considered: NO2 as an indicator of traffic-related pollution and SO2 as an indicator of heating-related pollution. To assess the association between these indicators and the risk of lung cancer, the study uses a geographic information system to track the subjects’ successive places of residence and work and estimates cumulative individual exposure by retrospectively modeling pollutant emission levels over the past decades. The objective of the presented case-control study is to analyze the relationship between long-term individual exposure to traffic- or heating-related air pollution and the development of lung cancer among men aged 40 to 75 in Stockholm. Methodologically, the study design and consideration of confounding factors are sound and well-developed. Various types of bias (selection, information, confounding) thus appear to have been avoided or controlled. The literature review on the relationship between environmental exposure and lung cancer is very thorough, and the results are consistent with the literature. The calculation of the attributable risk of lung cancer due to air pollution, estimated at 10%, constitutes an important finding of the study. In conclusion, the significance of this article lies in the retrospective reconstruction of air pollution, specifically considering NO2 and SO2 as respective indicators of air pollution linked to road traffic and heating. It constitutes an important contribution to the study of the role of air pollution in lung cancer risk and, more generally, to the prevention of cancers linked to environmental pollution. (Excerpt from the article)