Association Between High Levels of Nitrogen Dioxide and Increased Cumulative Incidence of Lung Cancer in Patients with Idiopathic Pulmonary Fibrosis.

BACKGROUND: Lung cancer is a fatal complication of idiopathic pulmonary fibrosis (IPF) with a poor prognosis. However, the association between individual exposure to air pollutants and lung cancer development in patients with IPF is unknown. This study aimed to assess the effect of individual exposure to nitrogen dioxide (NO2 ) on lung cancer development in patients with IPF.

METHODS: We enrolled 1085 patients from the IPF cohort (mean age: 65.6 years, male: 80.6%). We estimated individual-level long-term exposures to NO2 at the patient's residential addresses using a national-scale exposure prediction model based on the data from air quality regulatory monitoring stations. To evaluate the association between NO2 levels and lung cancer development in IPF, we used an individual- and area-level covariates adjusted model as our primary model.

RESULTS: The estimated average annual NO2 concentration was 23.1 parts per billion (ppb). During a follow-up of 4.3 years (median), 86 patients (7.9%) developed lung cancer. NO2 concentration was associated with lung cancer development in an unadjusted model (hazard ratio [HR], 1.219; p=0.042), while a marginal association was found in the primary model (HR 1.280; p=0.084). When NO2 concentration was divided by the median value (21.0 ppb), exposure to high NO2 levels (≥ 21.0 ppb) was associated with a 2.0-fold increase in the risk of lung cancer development (HR, 2.023; p=0.047) in the primary model.

CONCLUSION: Individual exposure to high NO2 levels may increase the risk of lung cancer development in patients with IPF.