Differences in the morbidity of asthma in multi temperature zones under short-term exposure to air pollution: a systematic review.

Different geographical locations and climatic environments lead to different impacts of specific air pollutants on the relative risk (RR) of asthma morbidity (i.e., new-onset asthma, outpatient visits, emergency department visits, and hospital admissions) in the Northern Hemisphere. Therefore, it is necessary to integrate existing data to assess the impact of short-term exposure to pollutants on the RR of asthma morbidity in the Northern Hemisphere. We conducted a systematic review and meta-analysis to evaluate the effects of short-term exposure to particulate matter (PM2.5, PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) on the RR of asthma morbidity. A comprehensive literature search was performed across three major databases: Web of Science, China National Knowledge Infrastructure (CNKI), and PubMed. Ultimately, 14 studies were included in the final analysis. Heterogeneity was evaluated using the Cochran Q test and I² statistics, and publication bias was assessed using Egger's test. The meta-analysis revealed that short-term exposure to five types of air pollutants had a significant impact on the RR of asthma morbidity. Among them, NO2 exhibited the most significant adverse health effects (RR = 1.02, 95% CI: 1.01-1.03). Stratified analysis showed that residents in the temperate regions were more affected by exposure to SO2, NO2, and O3, whereas residents in the tropical regions were more affected by PM10, and the regional differences in the impact of PM2.5 on the health of residents in the two regions were not significant. The Egger's test results suggested the presence of a potential publication bias for PM2.5 and SO2. In contrast, for PM10, NO2, and O3, no publication bias was detected. Therefore, an efficient and resilient public health system should be established.