Analysis of the impact of atmospheric O_{3-8 h} concentration on resident emergency admissions in Lanzhou City, China, 2014—2022

Objective  To investigate the trend of O_{3-8 h} concentration in Lanzhou City over the past decade and its relationships with the total emergency admissions as well as the admissions by sex and age, and to provide a reference for effectively preventing and controlling atmospheric O_{3-8 h} pollution in Lanzhou City, China.

Methods  The daily average concentrations of five atmospheric pollutants (O_{3-8 h}, PM₁₀, PM_2.5, NO₂, and SO₂), meteorological data, and emergency case data from 2014 to 2022 in Lanzhou City were collected. A distributed lag nonlinear model was used to analyze the relationships of atmospheric O_{3-8 h} concentration with the non-accidental emergency admissions as well as the emergency admissions by sex and age of residents.

Results  The average O_{3-8 h} concentration from 2014 to 2022 was 97.11 μg/m³ (4.00-350.00 μg/m³). The daily total emergency admissions, emergency admissions of male and female patients, emergency admissions of patients aged 0-14, 15-64, and 65 and above were 112, 64, 47, 4, 64, and 43, respectively. Compared with the 25th percentile (P₂₅) as a reference concentration, when the O_{3-8 h} concentration reached the 95th percentile (P₉₅), the strongest single-day lag effect on the daily emergency admissions, male patient emergency admissions, female patient emergency admissions, middle and high age groups emergency admissions were on lag0 d relative risk (RR)=1.023, 95% confidence interval (CI): 1.007-1.039, RR=1.016, 95% CI: 0.997-1.035, RR=1.034, 95% CI: 1.012-1.057, RR=1.019, 95% CI: 1.000-1.039, RR=1.033, 95% CI: 1.009-1.058, and the strongest cumulative lag effects were on lag0-3 d, lag0-7 d, lag0-2 d, lag0-5 d(relative risk RR=1.050, 95% CI: 1.017-1.085, RR=1.037, 95% CI: 0.997-1.078, RR=1.087, 95% CI: 1.019-1.160, RR=1.034, 95% CI: 0.998-1.072, RR=1.086, 95% CI: 1.023-1.153).The O_{3-8 h} exposure-response relationship between pollution and emergency admissions was approximately linear, while the O_{3-8 h} exposure-response relationship between pollution and emergency admissions of patients aged 15-64 was U-shaped. For the elderly group, as the lagging days increased, the reaction curve increased at a faster rate with the increase in concentration. The emergency admission rate of the elderly group was more sensitive to short-term O_{3-8 h} exposure compared with those of the young and middle-aged groups. Moreover, females were more sensitive to O_{3-8 h} pollution than males.

Conclusion  The atmospheric O_{3-8 h} pollution in Lanzhou City may increase the risk of non-accidental emergency admissions for residents, targeted prevention and control measures should be formulated for groups with different sensitivities.