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This study aimed to explore microbial aerosol distribution characteristics in the dental clinic during ultrasonic scaling and evaluate the effects of three different interventions on aerosol distribution and protective effects. For twenty minutes, ultrasonic scaling was carried out in a standardized operatory room. A blank control group and three intervention groups were created: high-volume evacuator (HVE), plasma purification (PP), and fenestrated ventilation (VT). The mass concentration of PM1.0, PM2.5, and PM10.0 aerosol particles was tracked in real time, and colony counts were calculated using air deposition. After ultrasonic scaling, there was a significant increase in aerosol dispersion of various particle sizes and distribution within a 1.5-m radius of the core area (P < 0.05). The number of colonies in each group varied over time at 0.5 and 1.0 m from the patient's head, but there was no significant difference at 1.5 m (P > 0.05). The PP group demonstrated the greatest decrease in aerosol mass concentration difference. The VT group initially had the lowest aerosol mass concentration difference, but with a slight decrease. The aerosol mass concentration difference between the HVE groups grew with distance. Traditional ultrasonic scaling poses a risk of aerosol contamination during and after treatment. The operatory room's air can be efficiently purified by plasma purification, which maintains lower levels of aerosol particle size than other groups. Microbial aerosols created by ultrasonic scaling can be quickly reduced by ventilation. At close range, the high-volume evacuator can lower the risk of infection while the benefit diminishes as the distance increases.Trial registration: This study was registered on the website of China Clinical Trial Registration Center (ChiCTR2400090751) (12/10/2024).

The formation of carbonyls and epoxides in e-cigarette (EC) aerosol is possible due to heating of the liquid constituents. However, high background levels of these compounds have inhibited a clear assessment of exposure during use of ECs. An EC containing an e-liquid replaced with 10% of 13C-labeled propylene glycol and glycerol was used in a controlled use clinical study with 20 EC users. In addition, five smokers smoked cigarettes spiked with the described e-liquid. Seven carbonyls (formaldehyde, acetaldehyde, acrolein, acetone, crotonaldehyde, methacrolein, propionaldehyde) were measured in the aerosol and the mainstream smoke. Corresponding biomarkers of exposure were determined in the user’s urine samples. 13C-labeled formaldehyde, acetaldehyde and acrolein were found in EC aerosol, while all seven labeled carbonyls were detected in smoke. The labeled biomarkers of exposure to formaldehyde (13C-thiazolidine carboxylic acid and 13C-N-(1,3-thiazolidine-4-carbonyl)glycine), acrolein (13C3-3-hydroxypropylmercapturic acid) and glycidol (13C3-dihydroxypropylmercapturic acid) were present in the urine of vapers indicating an EC use-specific exposure to these toxicants. However, other sources than vaping contribute to a much higher extent by several orders of magnitude to the overall exposure of these toxicants. Comparing data for the native (unlabeled) and the labeled (exposure-specific) biomarkers revealed vaping as a minor source of user’s exposure to these toxicants while other carbonyls and epoxides were not detectable in the EC aerosol.

Aim This study aims to evaluate the effectiveness of various cleaning methods in reducing airborne endotoxin and microbial aerosols during oral cleaning procedures. Method Forty patients undergoing oral cleaning procedures were randomly assigned to one of four groups ( n  = 10 per group). Group A received strong suction alone; Group B received strong suction combined with an air disinfection machine; Group C received strong suction combined with a dental electric suction machine; Group D received strong suction in conjunction with both an air disinfection machine and a dental electric suction machine. Airborne aerosol concentrations were assessed at four-time points: before treatment, 30 min into treatment, immediately after treatment, and 60 min after treatment ended. Samples were collected at distances of 20 cm, 60 cm, and 1 m from the patient’s oral cavity using the natural sedimentation method. T-test was used to evaluate the difference among tested groups. Results Airborne endotoxins and microbial aerosols levels increased significantly during treatment, with the highest levels observed at 20 cm from the patient’s mouth. During treatment, groups with additional cleaning methods (Groups B, C, and D) exhibited higher levels of airborne endotoxins and microbial aerosols compared to Group A (strong suction alone). However, post-treatment analysis revealed that Group D demonstrated the lowest level of airborne endotoxins and microbial aerosols, while Group A exhibited the highest. Conclusions Implementing effective aerosol management strategies can significantly reduce aerosol dispersion in the oral clinical environment. Continuous monitoring aerosol concentrations and the application of appropriate control measures are essential for minimizing infection risks for both patients and healthcare providers during oral cleaning procedures.

Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO₂ by NO₂ is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH₃ neutralization or under cloud conditions. Under polluted environments, this SO₂ oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH₃ and NO₂ control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

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.

Remarkable perturbations in the stratospheric abundances of chlorine species and ozone were observed over Southern Hemisphere mid-latitudes following the 2020 Australian wildfires 1 , 2 . These changes in atmospheric chemical composition suggest that wildfire aerosols affect stratospheric chlorine and ozone depletion chemistry. Here we propose that wildfire aerosol containing a mixture of oxidized organics and sulfate 3 – 7 increases hydrochloric acid solubility 8 – 11 and associated heterogeneous reaction rates, activating reactive chlorine species and enhancing ozone loss rates at relatively warm stratospheric temperatures. We test our hypothesis by comparing atmospheric observations to model simulations that include the proposed mechanism. Modelled changes in 2020 hydrochloric acid, chlorine nitrate and hypochlorous acid abundances are in good agreement with observations 1 , 2 . Our results indicate that wildfire aerosol chemistry, although not accounting for the record duration of the 2020 Antarctic ozone hole, does yield an increase in its area and a 3–5% depletion of southern mid-latitude total column ozone. These findings increase concern 2 , 12 , 13 that more frequent and intense wildfires could delay ozone recovery in a warming world. Comparison of model simulations with atmospheric observations from the Southern Hemisphere mid-latitudes following the 2020 Australian wildfires shows that the wildfire aerosol composition promotes stratospheric chlorine and ozone depletion chemistry.

The cooling of the Earth’s climate through the effects of anthropogenic aerosols on clouds offsets an unknown fraction of greenhouse gas warming. An increase in the amount of water inside liquid-phase clouds induced by aerosols, through the suppression of rain formation, has been postulated to lead to substantial cooling, which would imply that the Earth’s surface temperature is highly sensitive to anthropogenic forcing. Here we provide direct observational evidence that, instead of a strong increase, aerosols cause a relatively weak average decrease in the amount of water in liquid-phase clouds compared with unpolluted clouds. Measurements of polluted clouds downwind of various anthropogenic sources—such as oil refineries, smelters, coal-fired power plants, cities, wildfires and ships—reveal that aerosol-induced cloud-water increases, caused by suppressed rain formation, and decreases, caused by enhanced evaporation of cloud water, partially cancel each other out. We estimate that the observed decrease in cloud water offsets 29% of the global climate-cooling effect caused by aerosol-induced increases in the concentration of cloud droplets. These findings invalidate the hypothesis that increases in cloud water cause a substantial climate cooling effect and translate into reduced uncertainty in projections of future climate. Satellite data for cloud tracks downwind of major pollution sources show a relatively small global average decrease in cloud water caused by anthropogenic aerosols, invalidating claims that aerosol-induced effects contribute substantially to climate cooling.

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.

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions.

The link between biogenic volatile organic compounds in the atmosphere and their conversion to aerosol particles is unclear, but a direct reaction pathway is now described by which volatile organic compounds lead to low-volatility vapours that can then condense onto aerosol surfaces, producing secondary organic aerosol. From forest emission to aerosol Forests emit large quantities of volatile organic compounds to the atmosphere. The condensable oxidation products of volatile organic compounds emitted by forests can form secondary organic aerosols or SOAs that can affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. But our understanding of the link between biogenic volatile organic compounds and their conversion to aerosol particles remains limited. This study reveals that a direct reaction pathway can lead from volatile organic compounds to low-volatility vapours that can then condense onto aerosol surfaces producing secondary organic aerosol and can significantly enhance the formation and growth of aerosol particles over forested regions. Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol 1 , 2 , which is known to affect the Earth’s radiation balance by scattering solar radiation and by acting as cloud condensation nuclei 3 . The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours 4 , 5 , 6 , but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies 2 . We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere–aerosol–climate feedback mechanisms 6 , 7 , 8 , and the air quality and climate effects of biogenic emissions generally.