Objective To explore the association between short-term exposure to atmospheric fine particulate matter （PM_2.5） and ozone （O₃） and systemic inflammatory indicators in patients with pneumonia， and to identify the susceptible populations.

Methods From September 2018 to April 2020， data of 1 480 patients admitted for pneumonia was collected from a tertiary hospital in Taiyuan City. Generalized additive models （GAMs） were used to explore the associations between PM_2.5 and O₃ exposure and inflammatory indicators of patients with pneumonia； and to explore the susceptibility factors and susceptible populations to PM_2.5 and O₃ exposures through stratified analyses.

Results The short-term exposure to PM_2.5 was associated with changes in peripheral blood C-reation protein （CRP）， erythrocyte sedimentation （ESR）， easinophil （EOS）， neutrophil （NEU） and neutrophil-lymphocyte ratio （NLR） in patients with pneumonia， and there were different degrees of hysteresis effects， with the effect values reaching a maximum at lag03， lag03， lag0， lag03， lag03， respectively， which were 4.13% （95%CI： 0.43%‒7.84%）， 3.10% （95%CI： 0.24%‒5.97%）， 5.27% （95%CI： 3.12%‒7.42%）， 1.85% （95%CI： 0.36%‒3.34%）， and 2.53% （95%CI： 0.53%‒4.74%） for every 10 μg·m^-3 of PM_2.5. The changes in O₃ concentration were associated with the elevation of peripheral blood PCT and ESR in patients with pneumonia， and their effect values all reached the maximum at lag01 d， every 1 μg·m^-3 of O₃ elevation increased by 0.38% （95%CI： 0.04%‒0.73%） and 0.47% （95%CI： 0.19%‒0.76%）， respectively. Stratified analyses showed that the associations of PM_2.5 with peripheral blood CRP， ESR， NEU， and NLR in pneumonia patients were more significant in males， the elderly， and those with onset in the cold season； the associations of O₃ with peripheral blood PCT and ESR in pneumonia patients were more significant in the elderly and those with onset in the warm season， and the peripheral blood CRP and PCT in female patients with pneumonia were more susceptible to the changes of O₃.

Conclusion Short-term exposure to atmospheric PM_2.5 and O₃ are positively associated with changes in inflammatory indicators in patients with pneumonia， and the effects of PM_2.5 on patients with pneumonia are more extensive than those of O₃， with a longer lag effect. In addition， elderly patients with pneumonia are more sensitive to air pollution， male patients with pneumonia are more sensitive to PM_2.5， and female patients with pneumonia are more sensitive to O₃. Cold and warm seasons can exacerbate the effects of PM_2.5 and O₃ on inflammatory indicators in patients with pneumonia， respectively， and the patients must be protected well.