Supplementary Material for: A Time-Series Study of the Effect of Air Pollution on Outpatient Visits for Acne Vulgaris in Beijing

Background/Aims: There is increasing evidence that exposure to air pollutants, including particulate matter (PM_2.5, PM₁₀), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂), might aggravate preexisting skin diseases such as eczema and urticaria. Here we investigated if a possible link exists between air pollution and acne vulgaris. We assessed the association between ambient air pollutant concentrations and the number of visits of patients for acne vulgaris to a dermatological outpatient clinic in Beijing, China, from April 1, 2012 to April 30, 2014. Methods: In this time period, 59,325 outpatient visits were recorded because of acne vulgaris. Daily air pollution parameters for PM₁₀, PM_2.5, SO₂, and NO₂ were obtained from the Beijing Municipal Environmental Monitoring Center. Results: Increased concentrations of ambient PM_2.5, PM₁₀, and NO₂ were significantly associated with increased numbers of outpatient visits for acne vulgaris over the 2 years. These effects could be observed for NO₂ in a single-pollutant model and for PM_2.5, PM₁₀, and NO₂ in 2-pollutant models, which are closer to real-life exposure. Of note, these effects were specific because they were not observed for increased SO₂ concentrations, which even showed negative correlations in all test models. Conclusion: This study provides indirect evidence for a link between acne vulgaris and air pollution.