Objective  To explore the impact of air pollution on the number of outpatient visits for respiratory diseases and its seasonal change among residents of different gender and age in Mudanjiang city of Heilongjiang province and to provide evidences for the prevention of air pollution-related respiratory diseases in the city.

  Methods  Medical records of 8 943 515 outpatient clinic and emergency department visits from January 2015 through December 2016 were extracted at all hospitals in Mudanjiang city and data on ambient air sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5) were also collected simultaneously. Generalized additive model (GAM) was adopted to analyze the relationship between air pollution and outpatient visits for respiratory diseases.

  Results  The predominant effects of air pollutants on respiratory disease visits were observed at lag day 1, lag day 2, and lag day 0 for PM_2.5, NO₂, and SO₂ respectively. A 10 μg/m³ increase in PM_2.5, NO₂, and SO₂ were correlated with 3.981 % (95 % confidence interval 95 % CI: 2.746 % – 5.216 %), 6.938 % (5.017 % – 8.859 %), and 9.873 % (7.454 % – 12.292 %) increment in respiratory disease visits. The females were more susceptible to adverse effects of the air pollutants than the males and the children and the elderly were more vulnerable to the impact of air pollutants than the adults. A 10 μg/m³ increase in PM_2.5 was associated with the increases of 3.308 % (2.331 % – 4.285 %), 1.667 % (0.821 % – 2.521 %), and 2.912 % (2.149 % – 3.675 %) in the visits of male respiratory disease outpatients aged ≤ 18, 18 – 65, and ≥ 65 years; while the visits of female respiratory disease outpatients at ages of ≤ 18, 18–65, and ≥ 65 years increased by 3.517 % (2.362 % – 4.672 %), 1.839 % (0.985 % – 2.639 %), and 3.233 % (2.459 % – 4.007 %), respectively. The adverse impact of NO₂ and SO₂ on respiratory illness were observed only in the children and the elderly, but not in the adults.

  Conclusion  The adverse influence of air pollution on the incidence of respiratory diseases is more severe among the females than among the males and severe among the elderly of ≥ 65 years old and the children of ≤ 18 years old in Mudanjiang city.