Exposure to ambient air pollution is associated with an increased risk for lung cancer, particularly adenocarcinoma, a large European cohort study indicates.
The association was driven by exposure to particulate matter with diameters of less than 10 µm (PM10) and less than 2.5 µm (PM2.5), and occurred at concentrations below current European Union limit values.
“Particulate matter air pollution is ubiquitous, and on the basis of our results, further reductions in particulate matter air pollution can be expected to reduce the number of lung cancer cases in Europe,” say Ole Raaschou-Nielsen (Danish Cancer Society Research Center, Copenhagen) and fellow investigators writing in the Lancet Oncology.
The team analyzed data obtained by the European Study of Cohorts for Air Pollution Effects (ESCAPE) – a prospective investigation into the effects of exposure to air pollution on human health in Europe.
They included 17 cohort studies located in 12 areas of nine European countries. A total of 312,944 individuals contributed 4,013,131 person–years at risk, with 2095 incident lung cancer cases occurring over an average follow-up of 12.8 years.
Each participant’s exposure to air pollution was estimated based on the proximity of their residential address to different types of land-use, such as industry, roads, and ports. A comprehensive set of pollutants was assessed along with two traffic indicators, namely, traffic intensity on the nearest street and total traffic load on all roads within 100 meters.
Meta-analysis revealed significant associations between lung cancer and three separate air pollution variables: levels of PM10, levels of PM2.5, and total local traffic load, with adjusted hazard ratios (HRs) of 1.22 per 10 µg/m³, 1.18 per 5 µg/m³, and 1.09 per 4000 vehicle–km/day, respectively.
The association was also stronger for people who had lived at the same address throughout follow-up, with HRs of 1.48 and 1.33 for levels of PM10 and PM2.5, respectively.
Analysis by histologic subtype revealed that the association was strongest for adenocarcinomas, with HRs of 1.51 and 1.55 for levels of PM10 and PM2.5, respectively, while there was a non-significant association with squamous cell carcinomas.
Lung cancer risk was not associated with ambient levels of nitric oxide or traffic intensity on the nearest street.
Noting that their study benefited from “standardised exposure assessment, a large number of participants, information about potential confounders, and a virtually complete follow-up,” the team concludes: “This very large multicentre study shows an association between exposure to particulate matter air pollution and the incidence of lung cancer, in particular adenocarcinoma, in Europe, adding substantially to the weight of the epidemiological evidence.”