Long-term exposure to air pollution and lung cancer incidence in the Danish Nurse Cohort study

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Although the link between air pollution and lung cancer is well established, recent evidence from low-pollution areas is mixed. We investigated the association of long-term exposure to air pollution with lung cancer incidence in Denmark. We analyzed data from 28,731 female nurses in the Danish Nurse Cohort, followed from 1993/1999 until 2020 for lung cancer incidence. We estimated residential annual mean concentrations of particulate matter (PM 10 and PM 2.5 ), nitrogen dioxide (NO 2 ), black carbon (BC), and ozone (O 3 ) using the DEHM/UBM/AirGIS modelling system. Time-varying Cox regression models evaluated the associations between these exposures and lung cancer incidence. After excluding participants who did not meet the criteria for our study, we were left with 23,706 participants, 450 of whom developed lung cancer during the study period. The mean PM 2.5 , PM 10 , NO 2 , BC, and O 3 concentrations at the participants' baseline addresses were 14.65, 21.02, 20.25, 0.92, and 50.77 μg/m 3 , respectively. Our study found no association between the pollutants investigated and lung cancer incidence. Hazard ratios (HRs) and 95% confidence intervals for lung cancer incidence associated with 5-year moving average exposures to PM 2.5 , PM 10 , NO 2 , BC, and O 3 were 0.95 (0.75-1.20) per 2.68 μg/m 3 , 0.93 (0.78-1.12) per 2.81 μg/m 3 , 0.95 (0.83-1.08) per 7.98 μg/m 3 , 0.96 (0.86-1.08) per 0.34 μg/m 3 , and 1.05 (0.90-1.21) per 7.04 μg/ m 3 , respectively, in the fully adjusted model. These findings were robust across various statistical models and sensitivity analyses. We found no association between long-term air pollution exposure and lung cancer incidence in Danish female nurses, contrasting with established links in other contexts but aligning with recent studies in low-exposure settings. • We followed 23,706 Danish nurses over an average of 23 years for lung cancer incidence. • Nearly 40 years of air pollution data, including PM 2.5 , PM 10 , NO 2 , BC, and O 3 , were modeled according to the individual residential histories. • No association was detected between long-term exposure to ambient air pollution and lung cancer incidence, and this finding was robust through multiple sensitivity analysis. • Although contrasted to established links, our finding agreed well with recent studies in low-exposure settings.