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

<p><b><i>Background/Aims:</i></b> There is increasing evidence that exposure to air pollutants, including particulate matter (PM<sub>2.5</sub>, PM<sub>10</sub>), nitrogen dioxide (NO<sub>2</sub>), and sulfur dioxide (SO<sub>2</sub>), 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. <b><i>Methods:</i></b> In this time period, 59,325 outpatient visits were recorded because of acne vulgaris. Daily air pollution parameters for PM<sub>10</sub>, PM<sub>2.5</sub>, SO<sub>2</sub>, and NO<sub>2</sub> were obtained from the Beijing Municipal Environmental Monitoring Center. <b><i>Results:</i></b> Increased concentrations of ambient PM<sub>2.5</sub>, PM<sub>10</sub>, and NO<sub>2</sub> were significantly associated with increased numbers of outpatient visits for acne vulgaris over the 2 years. These effects could be observed for NO<sub>2</sub> in a single-pollutant model and for PM<sub>2.5</sub>, PM<sub>10</sub>, and NO<sub>2</sub> in 2-pollutant models, which are closer to real-life exposure. Of note, these effects were specific because they were not observed for increased SO<sub>2</sub> concentrations, which even showed negative correlations in all test models. <b><i>Conclusion:</i></b> This study provides indirect evidence for a link between acne vulgaris and air pollution.</p>