Search

Background: The incubation period is a crucial index of epidemiology in understanding the spread of the emerging Coronavirus disease 2019 (COVID-19). In this study, we aimed to describe the incubation period of COVID-19 globally and in the mainland of China. Methods: The searched studies were published from December 1, 2019 to May 26, 2021 in CNKI, Wanfang, PubMed, and Embase databases. A random-effect model was used to pool the mean incubation period. Meta-regression was used to explore the sources of heterogeneity. Meanwhile, we collected 11 545 patients in the mainland of China outside Hubei from January 19, 2020 to September 21, 2020. The incubation period fitted with the Log-normal model by the coarseDataTools package. Results: A total of 3235 articles were searched, 53 of which were included in the meta-analysis. The pooled mean incubation period of COVID-19 was 6.0 days (95% confidence interval [CI] 5.6–6.5) globally, 6.5 days (95% CI 6.1–6.9) in the mainland of China, and 4.6 days (95% CI 4.1–5.1) outside the mainland of China (P = 0.006). The incubation period varied with age (P = 0.005). Meanwhile, in 11 545 patients, the mean incubation period was 7.1 days (95% CI 7.0–7.2), which was similar to the finding in our meta-analysis. Conclusions: For COVID-19, the mean incubation period was 6.0 days globally but near 7.0 days in the mainland of China, which will help identify the time of infection and make disease control decisions. Furthermore, attention should also be paid to the region- or age-specific incubation period. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are a long-term environmental problem faced by human society. The sources of involuntary PAHs are complex, moreover, secondary emissions of fixed PAHs in the environment occur due to global change and disturbance of human activities. Samples of three environmental media including soil, air, and atmospheric bulk deposition were collected to observe the spatial distribution and seasonal variation, to discuss the source or sink of PAHs and their association with the air mass transport along the plain (Jianghan Plain, JHP) to mountain transect, and explore the geographic scope of the atmospheric transport influence. The results obtained showed that 16 individual PAHs generally existed in all environmental multimedia being studied, and the PAHs concentration in air, soil and deposition flux of atmospheric bulk was higher in JPH than in "Western Hubei Mountains" (WHMs). Considerably high PAHs concentrations were obtained from the soil, air and atmospheric bulk deposition in winter, summer, and both summer and winter, respectively. The air-soil fugacity fraction of PAHs indicated that the soil of Dajiuhu (DJH) is likely to be a sink. Backward air trajectory simulation confirmed that most of the air mass passes over the JHP before reaching DJH, combined with the (transport and persistence level III) TaPL3 model results JHP are acting as sources. However, seasonal changes lead to a shift in the roles of soil sources and sinks. The TaPL3 model calculated that PAHs are transported through water for a wider range of effects and a longer persistence, even up to 10 years. • Variations in spatial and seasonal of PAHs in a multimedium environment were observed. • Variations in spatial concentration of PAHs in soils and air are significant. • Fugacity fraction of PAHs suggested that Dajiuhu soils are likely to be a sink. • Seasonal changes lead to a shift in the roles of soil sources and sinks. • PAHs carried by air mass and water body have a wide range of transmission. [ABSTRACT FROM AUTHOR]

Huanggang City in central China, is a regional site connect with the north air mass from Xiangyang and Suizhou in Hubei Province and the eastern air mass from Dabie-shan which located at the junction of Hubei and Anhui Province. To enrich the aerosol database in central China and provide reference for the control of air pollution in Huanggang City and surrounding cities in central China, totally 62 PM 2.5 samples were collected during the year 2018 for season variation (January 2018–January 2019, once a week) and 16 priority PAHs were analyzed. The annual average concentrations of PM 2.5 and PM 2.5 -bound PAHs were 60.4 ± 38.6 μg m−3 and 7.35 ± 6.79 ng m−3, respectively. Positive matrix factorization (PMF) model showed that the main sources of PM 2.5 -bound PAHs were vehicle emissions (56.8%), coal and biomass burning (29.5%) and petroleum sources (13.7%). PM 2.5 and PM 2.5 -bound PAHs in Huanggang were mainly came from local emissions and relatively short-range transport and the high probability areas were concentrated in Hubei and Henan Province. The total incremental lifetime cancer risks (TILCR) values were ranged from 10−4 to 10−6, indicating the potential cancer risk for adults and children in Huanggang. However, ILCR ing and ILCR dem were four orders of magnitude higher than ILCR inh , indicating that ingestion and dermal contact were the main exposure routes for cancer. Vehicle emission contributed the most to TILCR (70.9%), followed by coal and biomass combustion (21.8%) and petroleum sources (7.39%). [Display omitted] 1. The correlation between meteorological parameters, PM 2.5 and PAHs in different seasons were investigated; 2. PMF and HYSPLIT model were used to explore the pollution sources and geographic origins, respectively; 3. Ingestion and dermal contact exposure has higher cancer risk than inhalation exposure; 4. Higher contribution of vehicle emissions to PAHs carcinogenic risk by PMF-ILCR model. [ABSTRACT FROM AUTHOR]