Fibrotic interstitial lung diseases and air pollution: a systematic literature review

BACKGROUND: Air pollution is hypothesised to be a risk factor for interstitial lung diseases (ILD). This study systematically reviewed the literature regarding the impact of air pollution on idiopathic pulmonary fibrosis (IPF) and fibrotic interstitial lung diseases (ILD). METHODS: A computer-assisted literature search of electronic databases was performed to identify studies focused on the association between ILDs and air pollution. Other inclusion criteria required that the article had to be: 1) original; 2) a prospective or retrospective study; and 3) fully published in English. Both randomised clinical trials and observational studies were considered. RESULTS: Only seven studies met the inclusion criteria. All studies investigated the relationship between pollution and IPF, except one that dealt with the relationship between pollution and hypersensitivity pneumonitis. Outcome measures included exacerbation of IPF, mortality, disease severity, prevalence of hypersensitivity pneumonitis, progression and incidence of IPF. On the whole, air pollution levels were negatively associated with outcomes in patients with IPF and fibrotic ILD outcome. The heterogeneity in the measurement and reporting of the end-points limited the performance of a quantitative synthesis of data. CONCLUSIONS: This systematic review provides supporting evidence linking exposure to air pollution to poor outcomes in patients with IPF and fibrotic ILD.