A study recently published in Respiratory Research showed that acute exposure to higher levels of air pollutants, including both particles and gases, was highly associated with hospitalizations due to idiopathic pulmonary fibrosis (IPF) in Beijing between 2013 and 2017. 

Liang and colleagues conducted an ecological study by compiling air pollution and hospitalization data from 2013 to 2017 and running time-series analyses to investigate the acute effects of such pollutants on IPF hospitalization risk in Beijing while also comparing them to archives from 2008 to 2012. The study recorded daily city-wide average concentrations of particulate matter with a diameter 10 μm (PM10) or 2.5 μm (PM2.5), nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2) from 35 municipal monitoring stations during the same period.

Additionally, the authors investigated whether the results differed by patients’ characteristics, including age, sex, seasonality, and respiratory comorbidities such as chronic obstructive pulmonary disease (COPD) and asthma.


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The most significant difference in air pollutants was in PM2.5. Compared to 2013 to 2017, the concentrations of PM2.5 observed from 2008 to 2012 were relatively higher and the lag time to hospitalization was longer (2 vs 5 days, respectively), conveying the importance of improved air quality in IPF morbidity and mortality.

“Our study has suggested that more acute exposure (ie, past three days) to PM2.5, as compared to more recent exposure (ie, past 30 days), was relatively more important in leading to IPF hospitalization,” the authors wrote.

Moreover, the acute exposure to O3 in the preceding 5 days correlated with IPF hospitalization. When stratifying the data by season, statistically significant associations arose only during the cold season. This specific result was unexpected since previous studies in Beijing and the northern part of China found that short-term effects of O3 on disease exacerbations and daily mortality were more pronounced during warm seasons.

Previous studies have shown that sources of PM10 in Beijing mainly come from dust. Traffic is the largest source of PM2.5, with coal combustion and biomass burning contributing primarily in the winter months. 

“To our best knowledge, this is by far the first and the largest time-series study that was conducted in a city with high levels of ambient air pollution, using a relatively large number of IPF hospitalizations over a 5-year period from a representative database,” the authors concluded.

IPF is the most common type of interstitial lung disease, characterized by inflammation and fibrosis of the pulmonary parenchyma. Its exact causes are still largely unknown, with some studies suggesting that inhaled exposures such as cigarette smoke or wood dust may be among the triggers. Patients with IPF experience progressive deterioration of lung function and impaired quality of life and have an estimated median survival of 3 to 5 years after diagnosis.

Reference

Liang L, Cai Y, Lyu B, et al. Air pollution and hospitalization of patients with idiopathic pulmonary fibrosis in Beijing: a time-series study. Respir Res. 2022;23(1):81. doi:10.1186/s12931-022-01998-8