Automotive braking is a source of highly charged aerosol particles.

Although the last several decades have seen a dramatic reduction in emissions from vehicular exhaust, nonexhaust emissions (e.g., brake and tire wear) represent an increasingly significant class of traffic-related particulate pollution. Aerosol particles emitted from the wear of automotive brake pads contribute roughly half of the particle mass attributed to nonexhaust sources, while their relative contribution to urban air pollution overall will almost certainly grow coinciding with vehicle fleet electrification and the transition to alternative fuels. To better understand the implications of this growing prominence, a more thorough understanding of the physicochemical properties of brake wear particles (BWPs) is needed. Here, we investigate the electrical properties of BWPs as emitted from ceramic and semi-metallic brake pads. We show that up to 80% of BWPs emitted are electrically charged and that this fraction is strongly dependent on the specific brake pad material used. A dependence of the number of charges per particle on charge polarity and particle size is also demonstrated. We find that brake wear produces both positive and negative charged particles that can hold in excess of 30 elementary charges and show evidence that more negative charges are produced than positive. Our results will provide insights into the currently limited understanding of BWPs and their charging mechanisms, which potentially have significant implications on their atmospheric lifetimes and thus their relevance to climate and air quality. In addition, our study will inform future efforts to remove BWP emissions before entering the atmosphere by taking advantage of their electric charge.

The Significant Role of New Particle Composition and Morphology on the HNO3-Driven Growth of Particles down to Sub-10 nm.

New particle formation and growth greatly influence air quality and the global climate. Recent CERN Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments proposed that in cold urban atmospheres with highly supersaturated HNO3 and NH3, newly formed sub-10 nm nanoparticles can grow rapidly (up to 1000 nm h-1). Here, we present direct observational evidence that in winter Beijing with persistent highly supersaturated HNO3 and NH3, nitrate contributed less than ∼14% of the 8-40 nm nanoparticle composition, and overall growth rates were only ∼0.8-5 nm h-1. To explain the observed growth rates and particulate nitrate fraction, the effective mass accommodation coefficient of HNO3 (αHNO3) on the nanoparticles in urban Beijing needs to be 2-4 orders of magnitude lower than those in the CLOUD chamber. We propose that the inefficient uptake of HNO3 on nanoparticles is mainly due to the much higher particulate organic fraction and lower relative humidity in urban Beijing. To quantitatively reproduce the observed growth, we show that an inhomogeneous "inorganic core-organic shell" nanoparticle morphology might exist for nanoparticles in Beijing. This study emphasized that growth for nanoparticles down to sub-10 nm was largely influenced by their composition, which was previously ignored and should be considered in future studies on nanoparticle growth.

Implications for new particle formation in air of the use of monoethanolamine in carbon capture and storage.

Alkanolamines are currently being deployed in carbon capture and storage (CCS) technology worldwide, and atmospheric emissions have been found to coincide with locations exhibiting elevated concentrations of methanesulfonic acid (MSA). It is thus critical to understand the fate and potential atmospheric reactions of these chemicals. This study reports the characterization of sub-10 nm nanoparticles produced through the acid-base reaction between gas phase monoethanolamine (MEA) and MSA, a product of organosulfur compound oxidation in air, using a flow reactor under dry and humid (up to ∼60% RH) conditions. Number size distribution measurements show that MEA is even more efficient than methylamine in forming nanoparticles on reaction with MSA. This is attributed to the fact that the MEA structure contains both an -NH2 and an -OH group that facilitate hydrogen bonding within the clusters, in addition to the electrostatic interactions. Due to this already strong H-bond network, water has a relatively small influence on new particle formation (NPF) and growth in this system, in contrast to MSA reactions with alkylamines. Acid/base molar ratios of unity for 4-12 nm particles were measured using thermal desorption chemical ionization mass spectrometry. The data indicate that reaction of MEA with MSA may dominate NPF under some atmospheric conditions. Thus, the unique characteristics of alkanolamines in NPF must be taken into account for accurate predictions of impacts of CCS on visibility, health and climate.

Design and testing of a sew-free origami mask for improvised respiratory protection.

Respiratory aerosols with diameters smaller than 100µm have been confirmed as important vectors for the spread of diseases such as SARS-CoV-2. While disposable and cloth masks afford some protection, they are typically inefficient at filtering these aerosols and require specialized fabrication devices to produce. We describe a fabrication technique that makes use of a folding procedure (origami) to transform any filtration material into a mask. These origami masks can be fabricated by non-experts at minimal cost and effort, provide adequate filtration efficiencies, and are easily scaled to different facial sizes. Using a mannequin fit test simulator, we demonstrate that these masks can provide filtration efficiencies of over 90% while simultaneously providing greater comfort as demonstrated by pressure drops of <20 Pa. We also quantify mask leakage by measuring the variations in filtration efficiency and pressure drop when masks are sealed to the mannequin face compared to when the mask is unsealed but positioned to achieve the best fit. While leakage generally trended with pressure drop, some of the best performing mask media achieved <10% reduction in filtration efficiency due to leakage. Because this mask can provide high filtration efficiencies at low pressure drop compared to commercial alternatives, it is likely to promote greater mask wearing tolerance and acceptance.

Formation of Highly Oxidized Organic Compounds and Secondary Organic Aerosol from α-Thujene Ozonolysis.

We conducted laboratory chamber experiments to probe the gas- and particle-phase composition of oxidized organics and secondary organic aerosol (SOA) formed from α-thujene ozonolysis under different chemical regimes. The formation of low-volatility compounds was observed using chemical ionization mass spectrometry with nitrate (NO3-) and iodide (I-) reagent ions. The contribution of measured low-volatility compounds to particle growth was predicted using a simple condensational growth model and found to underpredict the measured growth rates in our chamber (on the order of several nm min-1). The yields of low-volatility compounds and SOA mass were similar to those of other monoterpene ozonolysis systems. While semivolatile compounds C10H14-16O3-7 were measured most abundantly with I- reagent ion, a large fraction of products measured with NO3- were C5-7 fragments with predicted intermediate volatility. Additionally, particle composition was measured with ultrahigh-performance liquid chromatography with high-resolution mass spectrometry and compared to particle composition from α-pinene ozonolysis. Structural isomers were identified from tandem mass spectrometry analysis of two abundant product ions (C8H13O5-, C19H27O7-). Our results indicate that although this system efficiently generates low-volatility organics and SOA under the conditions studied, fragmentation pathways that produce more highly volatile products effectively compete with these processes.

Local variation in low carbon footprint inhalers in pre-COVID pandemic primary care prescribing guidelines for adult asthma in England and its potential impact.

AIMS: Pressurised metered-dose inhalers (MDIs) have a much higher carbon footprint than dry powder inhalers (DPIs). We aimed to describe variations of inhaler options in local adult asthma prescribing guidance. METHODS: We reviewed local clinical commissioning group (CCG) adult asthma prescribing guidance for primary care in England in 2019 and recorded DPI and MDI inclusion. The relationship to prescribing data from OpenPrescribing.net was examined. RESULTS: In total, 58 unique guidance documents were analysed covering 144 out of 191 CCGs in England. Only 3% of CCG guidelines expressed an overall preference for DPIs, while 12% explicitly preferred MDIs. The inclusion of DPIs first-line was 77% for short-acting ß-agonists, 78% for low-dose inhaled corticosteroid (ICS) inhalers and 90-96% for combination long-acting ß-agonist/ICS inhalers. MDIs were included first-line in 98-100% of these classes. In 26% of CCGs, there was no first-line DPI option for at least 1 asthma management step. Ten percent of CCGs had no DPI included first-line for any of the 5 classes examined. Many CCGs recommended higher carbon footprint options; Ventolin MDI (25.6%), inhalers containing HFA227ea (57.9%) and ICS regimes recommending 2 puffs of a lower dose over 1 puff of higher dose (94.2%). MDIs were prescribed more in CCGs that recommended them. CONCLUSION: Before the COVID pandemic, there was substantial variation between CCGs in adult asthma prescribing guidance regarding higher and lower carbon footprint options. There may still be scope to amend local guidance to improve clinical and environmental outcomes. This study provides a method and baseline for further investigation of this.

Insufficient Condensable Organic Vapors Lead to Slow Growth of New Particles in an Urban Environment.

Atmospheric new particle formation significantly affects global climate and air quality after newly formed particles grow above ∼50 nm. In polluted urban atmospheres with 1-3 orders of magnitude higher new particle formation rates than those in clean atmospheres, particle growth rates are comparable or even lower for reasons that were previously unclear. Here, we address the slow growth in urban Beijing with advanced measurements of the size-resolved molecular composition of nanoparticles using the thermal desorption chemical ionization mass spectrometer and the gas precursors using the nitrate CI-APi-ToF. A particle growth model combining condensational growth and particle-phase acid-base chemistry was developed to explore the growth mechanisms. The composition of 8-40 nm particles during new particle formation events in urban Beijing is dominated by organics (∼80%) and sulfate (∼13%), and the remainder is from base compounds, nitrate, and chloride. With the increase in particle sizes, the fraction of sulfate decreases, while that of the slow-desorbed organics, organic acids, and nitrate increases. The simulated size-resolved composition and growth rates are consistent with the measured results in most cases, and they both indicate that the condensational growth of organic vapors and H2SO4 is the major growth pathway and the particle-phase acid-base reactions play a minor role. In comparison to the high concentrations of gaseous sulfuric acid and amines that cause high formation rates, the concentration of condensable organic vapors is comparably lower under the high NOx levels, while those of the relatively high-volatility nitrogen-containing oxidation products are higher. The insufficient condensable organic vapors lead to slow growth, which further causes low survival of the newly formed particles in urban environments. Thus, the low growth rates, to some extent, counteract the impact of the high formation rates on air quality and global climate in urban environments.

Rapid cycling of reactive nitrogen in the marine boundary layer.

Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A 'renoxification' process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth's surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall.

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

Composition of Ultrafine Particles in Urban Beijing: Measurement Using a Thermal Desorption Chemical Ionization Mass Spectrometer.

Ultrafine particles (UFPs) dominate the particle number population in the urban atmosphere and revealing their chemical composition is important. The thermal desorption chemical ionization mass spectrometer (TDCIMS) can semicontinuously measure UFP composition at the molecular level. We modified a TDCIMS and deployed it in urban Beijing. Radioactive materials in the TDCIMS for aerosol charging and chemical ionization were replaced by soft X-ray ionizers so that it can be operated in countries with tight regulations on radioactive materials. Protonated N-methyl-2-pyrrolidone ions were used as the positive reagent ion, which selectively detects ammonia and low-molecular weight-aliphatic amines and amides vaporized from the particle phase. With superoxide as the negative reagent ion, a wide range of inorganic and organic compounds were observed, including nitrate, sulfate, aliphatic acids with carbon numbers up to 18, and highly oxygenated CHO, CHON, and CHOS compounds. The latter two can be attributed to parent ions or the decomposition products of organonitrates and organosulfates/organosulfonates, respectively. Components from both primary emissions and secondary formation of UFPs were identified. Compared to the UFPs measured at forest and marine sites, those in urban Beijing contain more nitrogen-containing and sulfur-containing compounds. These observations illustrate unique features of the UFPs in the urban environment and provide insights into their origins.

Molecular properties affecting the hydration of acid-base clusters.

In the atmosphere, water in all phases is ubiquitous and plays important roles in catalyzing atmospheric chemical reactions, participating in cluster formation and affecting the composition of aerosol particles. Direct measurements of water-containing clusters are limited because water is likely to evaporate before detection, and therefore, theoretical tools are needed to study hydration in the atmosphere. We have studied thermodynamics and population dynamics of the hydration of different atmospherically relevant base monomers as well as sulfuric acid-base pairs. The hydration ability of a base seems to follow in the order of gas-phase base strength whereas hydration ability of acid-base pairs, and thus clusters, is related to the number of hydrogen binding sites. Proton transfer reactions at water-air interfaces are important in many environmental and biological systems, but a deeper understanding of their mechanisms remain elusive. By studying thermodynamics of proton transfer reactions in clusters containing up to 20 water molecules and a base molecule, we found that that the ability of a base to accept a proton in a water cluster is related to the aqueous-phase basicity. We also studied the second deprotonation reaction of a sulfuric acid in hydrated acid-base clusters and found that sulfate formation is most favorable in the presence of dimethylamine. Molecular properties related to the proton transfer ability in water clusters are discussed.

Novel ionization reagent for the measurement of gas-phase ammonia and amines using a stand-alone atmospheric pressure gas chromatography (APGC) source.

RATIONALE: Contaminants present in ambient air or in sampling lines can interfere with the target analysis through overlapping peaks or causing a high background. This study presents a positive outcome from the unexpected presence of N-methyl-2-pyrrolidone, released from a PALL HEPA filter, in the analysis of atmospherically relevant gas-phase amines using chemical ionization mass spectrometry. METHODS: Gas-phase measurements were performed using a triple quadrupole mass spectrometer equipped with a modified atmospheric pressure gas chromatography (APGC) source which allows sampling of the headspace above pure amine standards. Gas-phase N-methyl-2-pyrrolidone (NMP) emitted from a PALL HEPA filter located in the inlet stream served as the ionizing agent. RESULTS: This study demonstrates that some alkylamines efficiently form a [NMP + amine+H]+ cluster with NMP upon chemical ionization at atmospheric pressure. The extent of cluster formation depends largely on the proton affinity of the amine compared with that of NMP. Aromatic amines (aniline, pyridine) and diamines (putrescine) were shown not to form cluster ions with NMP. CONCLUSIONS: The use of NMP as an ionizing agent with stand-alone APGC provided high sensitivity for ammonia and the smaller amines. The main advantages, in addition to sensitivity, are direct sampling into the APGC source and avoiding uptake on sampling lines which can be a significant problem with ammonia and amines.

Ab initio metadynamics calculations of dimethylamine for probing pKb variations in bulk vs. surface environments.

The basicity constant, or pKb, is an intrinsic physical property of bases that gives a measure of its proton affinity in macroscopic environments. While the pKb is typically defined in reference to the bulk aqueous phase, several studies have suggested that this value can differ significantly at the air-water interface (which can have significant ramifications for particle surface chemistry and aerosol growth modeling). To provide mechanistic insight into surface proton affinity, we carried out ab initio metadynamics calculations to (1) explore the free-energy profile of dimethylamine and (2) provide reasonable estimates of the pKb value in different solvent environments. We find that the free-energy profiles obtained with our metadynamics calculations show a dramatic variation, with interfacial aqueous dimethylamine pKb values being significantly lower than in the bulk aqueous environment. Furthermore, our metadynamics calculations indicate that these variations are due to reduced hydrogen bonding at the air-water surface. Taken together, our quantum mechanical metadynamics calculations show that the reactivity of dimethylamine is surprisingly complex, leading to pKb variations that critically depend on the different atomic interactions occurring at the microscopic molecular level.

An Experimental and Modeling Study of Nanoparticle Formation and Growth from Dimethylamine and Nitric Acid.

The size-resolved composition of nanoparticles formed and grown through acid-base reactive uptake has been studied in the laboratory by reacting gas-phase nitric acid (HNO3) and dimethylamine (DMA) in a flow tube under dry (<5% RH) and humid (∼55% RH) conditions. Size-resolved nanoparticle composition was measured by a thermal desorption chemical ionization mass spectrometer over the diameter range of 9-30 nm. The nanoparticle geometric mean diameter grew in the presence of water compared to dry conditions. Acid/base ratios of HNO3-DMA particles at all measured sizes did not strongly deviate from neutral (1:1) in either RH condition, which contrasts with prior laboratory studies of nanoparticles made from sulfuric acid (H2SO4) and base. Theoretical methods were used to investigate the underlying chemical processes that explain observed differences in the compositions of HNO3-DMA and H2SO4-DMA particles. Calculations of HNO3-DMA cluster stability indicated that a 1:1 acid/base ratio has >107 smaller evaporation rates than any other acid/base ratio in this system, and measured nanoparticle composition confirm this to be the most stable pathway for growth up to 30 nm particles. This study demonstrates that nanoparticle formation and growth via acid-base reactive uptake of HNO3 and DMA follow the thermodynamic theory, likely because of both components' volatility.

High-resolution analysis of gene activity during the Xenopus mid-blastula transition.

The Xenopus mid-blastula transition (MBT) marks the onset of large-scale zygotic transcription, as well as an increase in cell cycle length and a loss of synchronous cell divisions. Little is known about what triggers the activation of transcription or how newly expressed genes interact with each other. Here, we use high-resolution expression profiling to identify three waves of gene activity: a post-fertilisation wave involving polyadenylation of maternal transcripts; a broad wave of zygotic transcription detectable as early as the seventh cleavage and extending beyond the MBT at the twelfth cleavage; and a shorter post-MBT wave of transcription that becomes apparent as development proceeds. Our studies have also allowed us to define a set of maternal mRNAs that are deadenylated shortly after fertilisation, and are likely to be degraded thereafter. Experimental analysis indicates that the polyadenylation of maternal transcripts is necessary for the establishment of proper levels of zygotic transcription at the MBT, and that genes activated in the second wave of expression, including Brachyury and Mixer, contribute to the regulation of genes expressed in the third. Together, our high-resolution time series and experimental studies have yielded a deeper understanding of the temporal organisation of gene regulatory networks in the early Xenopus embryo.

Could the Transition movement help solve the NHS's problems?

Background: The NHS Five Year Forward View identifies a range of approaches for addressing the NHS's challenges. The Transition movement helps communities to reframe and rebuild their world by working on issues such as climate change, food, community relationships and localizing the economy. Methods: This paper describes Transition using five short example projects and, informed by these, identifies mechanisms by which Transition could potentially help reduce pressure on the NHS. Results: Transition is characterized by people self-organizing to address local challenges with benefits arising from both the outcomes and the process of the projects. Transition may be able to help the NHS reframe change, prevent disease, improve staff well-being and increase local economic resilience. Discussion: The evidence base for the relationship between Transition and health is growing but is not yet well developed. This reflects the complexity of establishing an evidence base for wider determinants of health. There is substantial potential learning for those in the NHS about change outside formal institutional structures. Conclusions: Transition provides new ways of thinking and acting to develop greater 'community intelligence', which could help the NHS in the face of increasing pressures.

Worldwide data sets constrain the water vapor uptake coefficient in cloud formation.

Cloud droplet formation depends on the condensation of water vapor on ambient aerosols, the rate of which is strongly affected by the kinetics of water uptake as expressed by the condensation (or mass accommodation) coefficient, αc. Estimates of αc for droplet growth from activation of ambient particles vary considerably and represent a critical source of uncertainty in estimates of global cloud droplet distributions and the aerosol indirect forcing of climate. We present an analysis of 10 globally relevant data sets of cloud condensation nuclei to constrain the value of αc for ambient aerosol. We find that rapid activation kinetics (αc > 0.1) is uniformly prevalent. This finding resolves a long-standing issue in cloud physics, as the uncertainty in water vapor accommodation on droplets is considerably less than previously thought.

Secondary organic aerosol formation and organic nitrate yield from NO3 oxidation of biogenic hydrocarbons.

The secondary organic aerosol (SOA) mass yields from NO3 oxidation of a series of biogenic volatile organic compounds (BVOCs), consisting of five monoterpenes and one sesquiterpene (α-pinene, ß-pinene, Δ-3-carene, limonene, sabinene, and ß-caryophyllene), were investigated in a series of continuous flow experiments in a 10 m(3) indoor Teflon chamber. By making in situ measurements of the nitrate radical and employing a kinetics box model, we generate time-dependent yield curves as a function of reacted BVOC. SOA yields varied dramatically among the different BVOCs, from zero for α-pinene to 38-65% for Δ-3-carene and 86% for ß-caryophyllene at mass loading of 10 µg m(-3), suggesting that model mechanisms that treat all NO3 + monoterpene reactions equally will lead to errors in predicted SOA depending on each location's mix of BVOC emissions. In most cases, organonitrate is a dominant component of the aerosol produced, but in the case of α-pinene, little organonitrate and no aerosol is formed.

Country of Origin of Medical Products and Risk of Labour Rights Abuse: A Cross-Sectional Analysis Using Four Procurement Datasets.

Background Case studies have highlighted labour rights abuse in the manufacture of several healthcare products, but little is known about the scale of the problem or the specific products involved. We aimed to quantify and compare the overall and product-specific risks of labour rights abuse in the manufacture of healthcare products supplied to high-income settings using multiple datasets on the product country of origin (COO). Methods Public procurement data from South-Eastern Norway (n=23,972 products) were compared to datasets from three other high-income settings: procurement data from Cambridge University Hospitals, trade data from UN Comtrade, and registry data from the US Food and Drug Administration (FDA). In each dataset, the product COO was matched to the International Trade Union Confederation risk rating for labour abuse and deemed high-risk when rated 4, 5, or 5+. Results In the Norway data, 55.4% of products by value had a COO declared, 49.1% of which mapped as high-risk of labour rights abuses. COO was identified for 70/100 products in the Cambridge data, with COO matching high-risk at 59.9% by value. The level of risk for specific medical product categories varied between the Norway, US FDA, and UN Comtrade datasets, but those with higher proportional risk included medical/surgical gloves and electrosurgical products. Conclusion Evidence of high-risk of labour rights abuse in the manufacture of healthcare products present in these data indicates a likely high level of risk across the sector. There is an urgent need for global legislative and political reform, with a particular focus on supply chain transparency as a key mechanism for tackling this issue.