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The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood 1 – 3 . Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus. Aerodynamic analysis of SARS-CoV-2 RNA in two hospitals in Wuhan indicates that SARS-CoV-2 may have the potential to be transmitted through aerosols, although the infectivity of the virus RNA was not established in this study.

We examined the correlation between lung cancer incidence/mortality and country-specific socioeconomic development, and evaluated its most recent global trends. We retrieved its age-standardized incidence rates from the GLOBOCAN database, and temporal patterns were assessed from global databases. We employed simple linear regression analysis to evaluate their correlations with Human Development Index (HDI) and Gross Domestic Product (GDP) per capita. The average annual percent changes (AAPC) of the trends were evaluated from join-point regression analysis. Country-specific HDI was strongly correlated with age-standardized incidence (r = 0.70) and mortality (r = 0.67), and to a lesser extent GDP (r = 0.24 to 0.55). Among men, 22 and 30 (out of 38 and 36) countries showed declining incidence and mortality trends, respectively; whilst among women, 19 and 16 countries showed increasing incidence and mortality trends, respectively. Among men, the AAPCs ranged from −2.8 to −0.6 (incidence) and −3.6 to −1.1 (mortality) in countries with declining trend, whereas among women the AAPC range was 0.4 to 8.9 (incidence) and 1 to 4.4 (mortality) in countries with increasing trend. Among women, Brazil, Spain and Cyprus had the greatest incidence increase, and all countries in Western, Southern and Eastern Europe reported increasing mortality. These findings highlighted the need for targeted preventive measures.

Investigation of the chemical nature and sources of particulate matter at urban locations in four Chinese cities during a severe haze pollution event finds that the event was driven to a large extent by secondary aerosol formation. What caused China's atmospheric haze? Air pollution is an important environmental problem in China, but the factors contributing to the high levels of particulate matter present during haze pollution events remain poorly understood. This paper investigates the chemical nature and sources of particulate matter at urban locations in four Chinese cities during the severe haze pollution event of January 2013, and finds that the event was driven to a large extent by secondary aerosol formation. This indicates that mitigation strategies focused on primary particulate emissions alone are unlikely to be fully effective. Additional measures such as controlling emissions of volatile organic compounds from fossil fuel combustion (mostly coal and traffic) and biomass burning may be required if China's particulate pollution is to be reduced. Rapid industrialization and urbanization in developing countries has led to an increase in air pollution, along a similar trajectory to that previously experienced by the developed nations 1 . In China, particulate pollution is a serious environmental problem that is influencing air quality, regional and global climates, and human health 2 , 3 . In response to the extremely severe and persistent haze pollution experienced by about 800 million people during the first quarter of 2013 (refs 4 , 5 ), the Chinese State Council announced its aim to reduce concentrations of PM 2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometres) by up to 25 per cent relative to 2012 levels by 2017 (ref. 6 ). Such efforts however require elucidation of the factors governing the abundance and composition of PM 2.5 , which remain poorly constrained in China 3 , 7 , 8 . Here we combine a comprehensive set of novel and state-of-the-art offline analytical approaches and statistical techniques to investigate the chemical nature and sources of particulate matter at urban locations in Beijing, Shanghai, Guangzhou and Xi’an during January 2013. We find that the severe haze pollution event was driven to a large extent by secondary aerosol formation, which contributed 30–77 per cent and 44–71 per cent (average for all four cities) of PM 2.5 and of organic aerosol, respectively. On average, the contribution of secondary organic aerosol (SOA) and secondary inorganic aerosol (SIA) are found to be of similar importance (SOA/SIA ratios range from 0.6 to 1.4). Our results suggest that, in addition to mitigating primary particulate emissions, reducing the emissions of secondary aerosol precursors from, for example, fossil fuel combustion and biomass burning is likely to be important for controlling China’s PM 2.5 levels and for reducing the environmental, economic and health impacts resulting from particulate pollution.

Vaccine hesitancy is among the major threats to the effectiveness of vaccination programmes. This study aimed to report the trend in response to willingness to accept the COVID-19 vaccine between two waves of the local epidemic and examine differences among occupations. Two cross-sectional surveys were conducted online during the first wave (February) and third wave (August to September) of the local epidemic in 2020. Acceptance of the COVID-19 vaccine was measured along with personal protection behaviours and occupations. A total of 2047 participants provided valid responses. The willingness to accept the COVID-19 vaccine among the participants was lower in the third wave (34.8%) than the first wave (44.2%). There were more concerns over vaccine safety in the third wave. Clerical/service/sales workers were less likely to accept the vaccine (adjusted odds ratio: 0.62, 95% confidence interval: 0.43–0.91). A high-level compliance of facemask wearing was found, and more people maintained social distancing and used alcohol hand rub in the third wave. Decreasing willingness to accept the COVID-19 vaccine may be associated with increasing concerns about vaccine safety and growing compliance of personal protection behaviours. The rush of vaccine development with higher risks of safety issues may jeopardize the public’s trust and lower uptake rates. Education and favourable policy should be provided to the general working population for the vaccination, especially for those who are not professional and are frequently exposed to crowds.

Brown carbon (BrC) contributes significantly to aerosol light absorption and thus can affect the Earth's radiation balance and atmospheric photochemical processes. In this study, we examined the light absorption properties and molecular compositions of water-soluble (WS-BrC) and water-insoluble (WI-BrC) BrC in PM2.5 collected from a rural site in the Guanzhong Basin – a highly polluted region in northwest China. Both WS-BrC and WI-BrC showed elevated light absorption coefficients (Abs) in winter (4–7 times those in summer) mainly attributed to enhanced emissions from residential biomass burning (BB) for heating of homes. While the average mass absorption coefficients (MACs) at 365 nm (MAC365) of WS-BrC were similar between daytime and nighttime in summer (0.99±0.17 and 1.01±0.18 m2 g−1, respectively), the average MAC365 of WI-BrC was more than a factor of 2 higher during daytime (2.45±1.14 m2 g−1) than at night (1.18±0.36 m2 g−1). This difference was partly attributed to enhanced photochemical formation of WI-BrC species, such as oxygenated polycyclic aromatic hydrocarbons (OPAHs). In contrast, the MACs of WS-BrC and WI-BrC were generally similar in winter and both showed few diel differences. The Abs of wintertime WS-BrC correlated strongly with relative humidity, sulfate and NO2, suggesting that aqueous-phase reaction is an important pathway for secondary BrC formation during the winter season in northwest China. Nitrophenols on average contributed 2.44±1.78 % of the Abs of WS-BrC in winter but only 0.12±0.03 % in summer due to faster photodegradation reactions. WS-BrC and WI-BrC were estimated to account for 0.83±0.23 % and 0.53±0.33 %, respectively, of the total down-welling solar radiation in the ultraviolet (UV) range in summer, and 1.67±0.72 % and 2.07±1.24 %, respectively, in winter. The total absorption by BrC in the UV region was about 55 %–79 % relative to the elemental carbon (EC) absorption.

Exposure models for some criteria of air pollutants have been intensively developed in past research; multi-air-pollutant exposure models, especially for particulate chemical species, have been however overlooked in Asia. Lack of an integrated model framework to calculate multi-air-pollutant exposure has hindered the combined exposure assessment and the corresponding health assessment. This work applied the land-use regression (LUR) approach to develop an integrated model framework to estimate 2017 annual-average exposure of multiple air pollutants in a typical high-rise and high-density Asian city (Hong Kong, China) including four criteria of gaseous air pollutants (particulate matter with an aerodynamic diameter equal to or less than 10 µm (PM10) and 2.5 µm (PM2.5), nitrogen dioxide (NO2), and ozone (O3)), as well as four major PM10 chemical species. Our integrated multi-air-pollutant exposure model framework is capable of explaining 91 %–97 % of the variability of measured gaseous air pollutant concentration, with the leave-one-out cross-validation R2 values ranging from 0.73 to 0.93. Using the model framework, the spatial distribution of the concentration of various air pollutants at a spatial resolution of 500 m was generated. The LUR model-derived spatial distribution maps revealed weak-to-moderate spatial correlations between the PM10 chemical species and the criteria of air pollutants, which may help to distinguish their independent chronic health effects. In addition, further improvements in the development of air pollution exposure models are discussed. This study proposed an integrated model framework for estimating multi-air-pollutant exposure in high-density and high-rise urban areas, serving an important tool for multi-air-pollutant exposure assessment in epidemiological studies.

PM2.5 is a major component of air pollution in China and has a serious threat to public health. It is very important to quantify spatial characteristics of the health effects caused by outdoor PM2.5 exposure. This study analyzed the spatial distribution of PM2.5 concentration (45.9 μg/m3 national average in 2016) and premature mortality attributed to PM2.5 in cities at the prefectural level and above in China in 2016. Using the Global Exposure Mortality Model (GEMM), the total premature mortality in China was estimated to be 1.55 million persons, and the per capita mortality was 11.2 per 10,000 persons in the year 2016, resulting in higher estimates compared to the integrated exposure‐response model. We assessed the premature mortality attributed to PM2.5 through common diseases, including ischemic heart disease (IHD), cerebrovascular disease (CEV), chronic obstructive pulmonary disease (COPD), lung cancer (LC), and lower respiratory infections (LRI). The premature mortality due to IHD and CEV accounted for 68.5% of the total mortality, and the per capita mortality (per 10,000 persons) for all ages due to IHD was 3.86, the highest among diseases. For the spatial distribution of disease‐specific premature mortality, the top two highest absolute numbers of premature mortality associated with IHD, CEV, LC, and LRI, respectively, were found in Chongqing and Beijing. In 338 cities of China, we have found a significant positive spatial autocorrelation of per capita premature mortality, indicating the necessity of coordinated regional governance for an efficient control of PM2.5. Plain Language Summary Fine particulate matter (PM2.5) concentrations have increased in general, in most developing countries in recent decades. In China, PM2.5 pollution has become a major component of air pollution and has serious health impacts. To obtain a comprehensive understanding of the national health impacts of PM2.5 in China, we have used the Global Exposure Mortality Model (GEMM) to estimate the premature mortality associated with PM2.5 exposure in 338 cities in China at the prefectural level and above. In addition, we analyzed the spatial distribution of premature mortality attributed to PM2.5 for five diseases, including ischemic heart disease (IHD), cerebrovascular disease (CEV), chronic obstructive pulmonary disease (COPD), lung cancer (LC), and lower respiratory infections (LRI). Our study finds that the total premature mortality associated with PM2.5 exposure in China for 2016 was 1.55 million persons. The top two highest absolute numbers of premature mortality associated with IHD, CEV, LC, and LRI, respectively were found in Chongqing and Beijing. Furthermore, cities with high per capita premature mortality tended to be spatially connected with other cities with high per capita premature mortality, indicating the coordinated regional governance should be adopted to reduce the impact of PM2.5 on human health. Key Points Based on an extended observational network in China, 1.55 million premature deaths attributed to PM2.5 is estimated in 2016 Higher premature mortality using the Global Exposure Mortality Model compared to the Integrated Exposure‐Response model A positive spatial autocorrelation of the per capita premature mortality is found at the city levels

To provide long-term air pollutant exposure estimates for epidemiological studies, it is essential to test the feasibility of developing land-use regression (LUR) models using only routine air quality measurement data and to evaluate the transferability of LUR models between nearby cities. In this study, we developed and evaluated the intercity transferability of annual-average LUR models for ambient respirable suspended particulates (PM10), fine suspended particulates (PM2.5), nitrogen dioxide (NO2) and ozone (O3) in the Taipei–Keelung metropolitan area of northern Taiwan in 2019. Ambient PM10, PM2.5, NO2 and O3 measurements at 30 fixed-site stations were used as the dependent variables, and a total of 156 potential predictor variables in six categories (i.e., population density, road network, land-use type, normalized difference vegetation index, meteorology and elevation) were extracted using buffer spatial analysis. The LUR models were developed using the supervised forward linear regression approach. The LUR models for ambient PM10, PM2.5, NO2 and O3 achieved relatively high prediction performance, with R2 values of > 0.72 and leave-one-out cross-validation (LOOCV) R2 values of> 0.53. The intercity transferability of LUR models varied among the air pollutants, with transfer-predictive R2 values of > 0.62 for NO2 and < 0.56 for the other three pollutants. The LUR-model-based 500 m × 500 m spatial-distribution maps of these air pollutants illustrated pollution hot spots and the heterogeneity of population exposure, which provide valuable information for policymakers in designing effective air pollution control strategies. The LUR-model-based air pollution exposure estimates captured the spatial variability in exposure for participants in a cohort study. This study highlights that LUR models can be reasonably established upon a routine monitoring network, but there exist uncertainties when transferring LUR models between nearby cities. To the best of our knowledge, this study is the first to evaluate the intercity transferability of LUR models in Asia.

Black carbon (BC) has important impact on climate and environment due to its light absorption ability, which greatly depends on its physicochemical properties including morphology, size and mixing state. The size distribution of the refractory BC (rBC) was investigated in urban Beijing in the late winter of 2014, during which there were frequent haze events, through analysis of measurements obtained using a single-particle soot photometer (SP2). By assuming void-free rBC with a density of 1.8 g cm−3, the mass of the rBC showed an approximately lognormal distribution as a function of the volume-equivalent diameter (VED), with a peak diameter of 213 nm. Larger VED values of the rBC were observed during polluted periods than on clean days, implying an alteration in the rBC sources, as the size distribution of the rBC from a certain source was relative stable, and VED of an individual rBC varied little once it was emitted into the atmosphere. The potential source contribution function analysis showed that air masses from the south to east of the observation site brought higher rBC loadings with more thick coatings and larger core sizes. The mean VED of the rBC presented a significant linear correlation with the number fraction of thickly coated rBC, extrapolating to be  ∼ 150 nm for the completely non-coated or thinly coated rBC. It was considered as the typical mean VED of the rBC from local traffic sources in this study. Local traffic was estimated to contribute 35 to 100 % of the hourly rBC mass concentration with a mean of 59 % during the campaign. Lower local traffic contributions were observed during polluted periods, suggesting increasing contributions from other sources (e.g., coal combustion and biomass burning) to the rBC. Thus, the heavy pollution in Beijing was greatly influenced by other sources in addition to the local traffic.

Heterogeneity between ambient and personal exposure to heavy metals has been documented. However, few studies have investigated potential health risks posed by inhalational exposure to airborne heavy metal(loid)s at the individual level. A total of 404 personal fine particles (PM2.5) samples were collected from 61 adult residents (aged 18–63 years) in Hong Kong during 2014–2015. Heavy metal(loid)s were analyzed using energy dispersive X-ray fluorescence. Among the analyzed heavy metal(loid)s, zinc (Zn) was the most abundant component in personal PM2.5, followed by lead (Pb), copper (Cu), and vanadium (V); cobalt (Co) and cadmium (Cd) were not detectable. Health risks of personal exposure to heavy metal(loid)s via inhalation were assessed for adults, including non-cancer risks that were characterized by hazard quotient (HQ) and hazard index (HI). The results indicated that non-cancer risks of heavy metal(loid)s were attributable to Cu, with a 95th HQ value > 1. Arsenic (As) and hexavalent chromium [Cr (VI)] were also significant contributors to inhalation cancer risks (> 1 × 10−6) for the adult participants. Finally, we employed a Monte Carlo simulation to evaluate the uncertainty associated with health risk assessment. The mean and median upper-bound lifetime cancer risk associated with inhalation exposure to carcinogenic heavy metal(loid)s exceeded the acceptable level (1 × 10−6) for adults. Traffic emission (including non-tailpipe exhaust), shipping emission, and regional pollution were significant sources of heavy metals. These findings suggest that emission controls targeting local vehicles and vessels should be given priority in Hong Kong.