Background Idiopathic pulmonary fibrosis (IPF) and idiopathic nonspecific interstitial pneumonia (INSIP) have recently been classified together as chronic fibrosing idiopathic interstitial pneumonia (IIP). Occupational and environmental factors are believed to be risk factors for the development of chronic pulmonary fibrosis. Previous case-control studies have suggested that occupational and environmental agents may contribute to the aetiology of IPF, but the association with INSIP has not been examined. Therefore, we aimed to evaluate the association of occupational and environmental agents with chronic fibrosing IIP, including INSIP.

Methods This was a retrospective case-control study performed at a university hospital in South Korea. We recruited patients with chronic fibrosing IIP diagnosed from January 2011 to December 2014 at a respiratory centre at our institute and randomly matched healthy controls who had normal chest X-ray findings by age and gender. Ninety-two chronic fibrosing IIP patients and 92 matched controls were analysed. We used a structured questionnaire to evaluate potential occupational and environmental risk factors for chronic fibrosing IIP, with adjustments for age, smoking, and clinical risk factors.

Results We used conditional logistic regression models to analyse associations with chronic fibrosing IIP adjusted for age, smoking and clinical risk factors. Exposure to stone, sand, or silica significantly increased the risk of chronic fibrosing IIP (odds ratio [OR]=5.01; 95% CI, 1.07–24.21).

Conclusions Our findings indicate that exposure to stone, sand, and silica might constitute a risk factor for developing chronic fibrosing IIP in the Korean population.