Air quality improvement assessment and exposure risk of Shandong Province in China during 2014 to 2020.

As one of the most polluted provinces in China, air pollution events occur frequently in Shandong. Based on the hourly (or daily) concentrations of six air pollutants (PM2.5, PM10, O3, NO2, SO2 and CO), the situations of air quality improvement in three kinds of cities (key cities, coastal cities and general cities) are assessed comprehensively during 2014-2020. Contrary to the daily maximum 8-h average ozone (MDA8 O3), the annual average concentrations of other pollutants show the downward trends during 2014-2020. Therein, the improvement rates of annual average concentrations of air pollutants in key cities are highest. By 2020, the day proportions of O3 as the primary pollutant are up to 38% in three kinds of cities. Besides, due to the impact of COVID-19, the monthly average concentrations of PM2.5, PM10, NO2, SO2 and CO in February 2020 decrease by 32.1-49.5% year-on-year. There are still about 50% of population exposed to high-risk regions (R i > 2), which are mainly concentrated in main urban areas and industrial areas. Thus, the adjustment of industrial structure and energy composition in the context of carbon peak and carbon neutrality should be implemented in the future. Supplementary Information: The online version contains supplementary material available at 10.1007/s13762-022-04651-5.

Asymptomatic transmission in the COVID-19 pandemic: A systematic review and meta-analysis

Objective To determine the differences in the epidemiological characteristics of asymptomatic patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 2019 (COVID-19) patients. Methods The relevant data of asymptomatic SARS-CoV-2 transmission literature in PubMed, Web of Science, CNKI, VIP medicine and Wanfang medical database were extracted as of August 1, 2020. Epidemiological information was screened and extracted according to pre-established inclusion and exclusion criteria. Age, gender, virus shedding duration and virual load of asymptomatic carriers were summarized and analyzed. Results A total of 38 articles met the criteria, 17 of which were asymptomatic case reports related to the virus shedding duration. Compared with symptomatic infected persons, asymptomatic individuals were younger [Weighted Mean Difference (WMD), WMD=-5.27, 95% CI: -9.78--0.76, P < 0.001] and the viral load was lower (WMD=2.36, 95% CI: 0.65-4.07, P=0.007). The virus shedding duration of asymptomatic individuals (median=11 days) was shorter than symptomatic patients (median=16 days). Conclusion Asymptomatic individuals with SARS-CoV-2 were younger, had a lower viral load and a shorter virus shedding duration than COVID-19 patients. © 2021, Publication Centre of Anhui Medical University. All rights reserved.