Ambient air pollution and hospital admission for interstitial lung diseases: A multicenter hospital-based case-crossover study

Interstitial lung diseases (ILDs) lead to increased morbidity and premature deaths, imposing a significant burden on public health worldwide. Recently, several studies have linked ambient air pollution with the acute exacerbation of certain ILDs, but the evidence remains limited and inconclusive. With a multicenter hospital-based case-crossover design, we investigated 9128 patients who resided in Jiangsu province, China, and were admitted for ILDs between 2019 and 2022. Residential exposure to particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM_2.5), PM₁₀, sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃) was assessed using our validated grid datasets. We fitted conditional logistic regression models to examine associations of exposure to air pollutants with ILD admission. A 10 µg/m³ increment of exposure to SO₂ and NO₂ was positively associated with a 16.18 % (95 % confidence interval [CI]: 3.79 %, 30.03 %) and 4.06 % (0.75 %, 7.49 %) increase in odds of ILD admission, respectively. All these associations appeared to be linear and the association of SO₂ exposure was significantly stronger among older adults. We estimated that over 10 % of ILD admissions could be attributable to exposure to SO₂ and NO₂. This study provides compelling evidence on the association of exposure to ambient air pollutants (including SO₂ and NO₂) with an increased odds of ILD hospitalizations. Our findings indicate that SO₂ and NO₂ exposures can lead to the exacerbation of ILDs, especially in elderly, and that the disease burden is considerable.