Respirable Fraction Research Articles

Prevalence of Autotrophy in Non-humic African Lakes

Heterotrophic respiration of organic matter (OM) is thought to dominate over aquatic primary production (PP) in most freshwater lake ecosystems. This paradigm implies that lateral transport of OM from the terrestrial biosphere subsidize the major fraction of aquatic respiration and that many lakes are a net source of carbon dioxide (CO2) to atmosphere. Nevertheless, African lakes were absent of the datasets upon which this paradigm was built. Here, we report a comprehensive and methodologically consistent data set of pelagic PP and community respiration (CR) obtained over the last decade in contrasting non-humic African lakes including 5 of the East African Great lakes (Tanganyika, Kivu, Edward, Albert, Victoria) and smaller shallow lakes located in Eastern Africa. Also, we determined the partial pressure of CO2 in surface waters and examined the sources and dynamics of organic and inorganic carbon by means of stable isotope tools across a wide range of physical and chemical conditions and productivity status. Our observations revealed that the threshold value at which the equivalence between PP and CR is met is substantially lower in Africa (10 mmol C m−3 d−1) than at higher latitude (25 mmol C m−3 d−1), suggesting that non-humic African lakes tend to be more autotrophic than expected from empirical relationships derived from data collected in boreal and temperate regions. Integrated at the regional scale, we estimate that PP is about 20 times higher than the organic carbon burial in sediments. It implies that a large fraction (< 90%) of PP is effectively recycled in the warm water column of non-humic African lakes.

Effect of Grit Size on Airborne Particle Concentration and Size Distribution during Oak Wood Sanding

Adverse health effects caused by exposure to airborne particles have been detected in recent years, however there is little knowledge about exposure to ultrafine particles with a diameter &lt;100 nm. In this study, particle number concentration and size distribution in a range of particle diameters from 10 nm to 10 µm were determined during oak wood sanding. A hand-held orbit sander in combination with three types of grit size (P60, 120 and 240) of sandpaper were used. Measurements were obtained using a portable particle size distribution analyzer and an optical particle size spectrometer, carried out at 15-min intervals for each treatment by static sampling in the breathing zone. We also compared the optical particle size spectrometer to the aerosol monitor in order to evaluate the mass concentration of airborne particles in the range of 1 to 10 µm in diameter. Sanding paper with the finest grit, P240, showed a significantly higher number concentration of ultrafine particles, compared with P60 and P120 grits. The differences among particular grit size were statistically significant for microparticles. The size distribution of particles during sanding was not affected by grit size. For each grit size, apparent peak values of ultrafine and microparticle number concentrations were determined at approximately 15 nm, and 0.1 µm, respectively. Optical particle size spectrometer and aerosol monitor showed comparable results of mass concentration for the respirable fraction.

Consistent diurnal pattern of leaf respiration in the light among contrasting species and climates.

Summary Leaf daytime respiration (leaf respiration in the light, R L) is often assumed to constitute a fixed fraction of leaf dark respiration (R D) (i.e. a fixed light inhibition of respiration (R D)) and vary diurnally due to temperature fluctuations.These assumptions were tested by measuring R L, R D and the light inhibition of R D in the field at a constant temperature using the Kok method. Measurements were conducted diurnally on 21 different species: 13 deciduous, four evergreen and four herbaceous from humid continental and humid subtropical climates. R L and R D showed significant diurnal variations and the diurnal pattern differed in trajectory and magnitude between climates, but not between plant functional types (PFTs). The light inhibition of R D varied diurnally and differed between climates and in trajectory between PFTs.The results highlight the entrainment of leaf daytime respiration to the diurnal cycle and that time of day should be accounted for in studies seeking to examine the environmental and biological drivers of leaf daytime respiration.

Silicose

Introduction/framework/objectives Pneumoconiosis are the most frequent occupational diseases. Silicosis is caused by inhaling breathable crystalline Silica. It is a diffuse interstitial fibronodular lung disease. Initially it is asymptomatic, however, it is usually progressive and without cure. The diagnosis is partially based on a history of professional exposure. It is more prevalent in countries with considerable unemployment and/or little or no Health and Safety Surveillance at Work. Methodology This is a Bibliographic Review, initiated through a search carried out in January 2022, in the databases “CINALH plus with full text, Medline with full text, Database of Abstracts of Reviews of Effects, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register, Nursing and Allied Health Collection: comprehensive, MedicLatina and RCAAP”. Contents Silica or silicon dioxide (SiO2) is made up of oxygen and silicon. In nature it exists in amorphous and crystalline forms. The International Agency for Research on Cancer (IARC) considered inhaled crystalline Silica as a human carcinogen (group 1), probably due to cellular damage, inflammation, oxidative stress and inhibition of clearance. Amorphous silica is not considered carcinogenic to humans (group 3). Silicosis exists in all countries, but is more prevalent in the ones less developed, even realizing that the real incidence should be higher than the official one, due to the situation being underreported. In more developed countries, the incidence/prevalence has decreased, due to the improvement of working conditions. Exposure is relevant via inhalation; cutaneous and digestive tracts generally do not have important consequences in the work context. The health risk varies with concentration, particle size– diameter, surface and shape (more dangerous if smaller), exposure time, type of silica (crystalline, tridymite and cristobalite are the most harmful, although more rare), density, water and lipid solubility, chemical reactivity, hygroscopic and electrostatic character, temperature, air speed and employee physical activity. Also important are gender, body area, age, general health status, previous pathologies and smoking- that is, individual susceptibility. The particles can be inhaled, thoracic or respirable (the latter are able to settle in the lungs). The shape, size and density of dust will affect the behavior and penetration into the respiratory system. The respirable fraction consists of particles smaller than 10 micrometers, that is, they can reach the area where gas exchange takes place; larger than that, they are usually deposited in the nasal and thoracic region. Silica nanoparticles smaller than 100 nanometers can reach the bloodstream. After inhalation, Silica particles are mainly deposited in the bronchioles and alveoli; if mucociliary clearance is not sufficient, inflammation (alveolitis) develops, which can lead to fibrosis and cancer. Macrophage activation generates free radicals/reactive oxygen species, which are not always attenuated by anti-oxidant defenses. Continued exposure enhances the release of cytokines which, in turn, activate more macrophages, neutrophils and lymphocytes; the increased production of collagen will then lead to said fibrosis, decreasing lung profitability and efficiency; that is, decreasing gas exchange; being that it can also reach the pleura. Discussion and Conclusions Despite the advances provided by an increasingly effective Health and Safety system, Silicosis is still a problem in some contexts, so it is necessary that the professionals working in these teams have reasonable knowledge regarding the sectors/tasks where it can occur, auxiliary diagnostic tests and other surveillance parameters, collective and individual protection measures, as well as possible implications for the classification of aptitude to work. It would be relevant to better understand the national scenario, through the dissemination of investigations carried out in this context. KEYWORDS: silica, silicosis, safety at work, occupational health and occupational medicine.

Ericaceous dwarf shrubs contribute a significant but drought‐sensitive fraction of soil respiration in a boreal pine forest

Abstract Boreal forests often have a dense understorey of ericaceous dwarf shrubs with ecological adaptations that contrast those of the canopy‐forming trees. It is therefore important to quantify contributions by understorey shrubs to ecosystem processes and disentangle shrub‐ and tree‐driven responses to climatic factors. We quantified soil respiration driven by the pine canopy and the ericaceous shrub understorey over 3 years, using a factorial pine root exclusion and shrub removal experiment in a mature Pinus sylvestris forest. Soil temperature and moisture‐related responses of respiration attributed to autotrophs (shrubs, pine roots) and heterotrophs were compared. Additionally, we assessed effects of interactions between these functional groups on soil nitrogen availability and respiration. Understorey shrubs accounted for 22% ± 10% of total autotrophic respiration, reflecting the ericaceous proportion of fine root production in the ecosystem. Heterotrophic respiration constituted about half of total soil respiration. Shrub‐driven respiration was more susceptible to drought than heterotrophic‐ and pine‐driven respiration. While the respiration attributed to canopy and understorey remained additive, indicating no competitive release, the plant guilds competed for soil N. Synthesis. Ericaceous understorey shrubs accounted for a small, yet significant, share of total growing season soil respiration. Overlooking understorey respiration may lead to erroneous partitioning and modelling of soil respiration mediated by functional guilds with contrasting responses to soil temperature and moisture. A larger contribution by heterotrophs and pine root‐associated organisms to soil respiration under drought conditions could have important implications for soil organic matter accumulation and decomposition as the climate changes in boreal forests.

Triclosan and ⍺-bisabolol–loaded nanocapsule functionalized with ascorbic acid as a dry powder formulation against A549 lung cancer cells

Lung cancer is between the primary causes of cancer death showing a high mortality rate. Traditional therapies lead to serious side-effects pushing the development of new and more specific treatments. This study proposes an innovative inhalable powder intended for lung cancer on-site action, by developing new nanocapsules functionalized powder formulation carrying triclosan, dispersed in α-bisabolol and functionalized with ascorbic acid. Nanocapsules were obtained by interfacial deposition of the preformed polymer method. Functionalization was performed via a three-step interfacial reaction process forming a chitosan-iron-ligand complex. After spray-drying, powders were obtained using two strategies. All formulations were characterized and had their antiproliferative activities tested, along with their irritability potential. Functionalized nanocapsules were subsequently spray-dried to produce dispersible powders. Using combined data from infrared spectroscopy was observed an interaction between the components after each step of the surface functionalization. The same components interactions were verified before and after obtaining the powder, which were adequate for lung administration, suffering deposition mainly in the respirable fraction within 15 min. The powder showed an effective concentration against lung cancer cells (A549), with nontoxic effects in irritability assay. By the results, the formulation can be administered at safe triclosan concentrations. Thus, the proposed formulations are appropriate and promising candidates for further research in lung cancer treatment.

Use of a Viral Filter to Reduce Exposure to Exhaled Aerosol Does Not Affect Methacholine Dose Delivery During Bronchoprovocation Testing.

Methacholine challenge testing (MCT) is a common bronchoprovocation technique used to assess airway hyper-responsiveness. We previously demonstrated that the addition of a viral filter to the nebulizer exhalation limb substantially reduced expelled particles during MCT. Our aim was to evaluate whether this modification affects the delivered dose of methacholine. A mechanical ventilator was connected to a lung simulator with breathing frequency 15 breaths/min, tidal volume 500 mL, inspiratory-expiratory ratio 1:1, with a sinusoidal waveform. We compared methacholine dose delivery using the Hudson Micro Mist or AeroEclipse II BAN nebulizers powered by either a dry gas source or a compressor system. A filter placed in line between the nebulizer and test lung was weighed before and after 1 min of nebulized methacholine delivery. Mean inhaled mass was measured with and without a viral filter on the exhalation limb. Dose delivery was calculated by multiplying the mean inhaled mass by the respirable fraction (particles < 5 μm) and inhalation time. Unpaired t test was used to compare methacholine dose delivery with and without viral filter placement. The addition of a viral filter did not significantly affect methacholine dose delivery across all devices tested. Using a 50-psi dry gas source, dose delivered with or without a viral filter did not differ with the Hudson (422.3 μg vs 282.0 μg, P = .11) or the AeroEclipse nebulizer (563.0 μg vs 657.6 μg, P = .59). Using the compressor, dose delivered with and without a viral filter did not differ with the Hudson (974.0 μg vs 868.0 μg, P = .03) or the AeroEclipse nebulizer (818.0 μg vs 628.5 μg, P = .42). The addition of a viral filter to the nebulizer exhalation limb did not affect methacholine dose during bronchoprovocation testing. Routine use of a viral filter should be considered to improve pulmonary function technician safety and infection control measures during the ongoing COVID-19 pandemic.

Rapid Assessment of Oxidative Damage Potential: A Comparative Study of Engineered Stone Dusts Using a Deoxyguanosine Assay.

The popularity of engineered stone (ES) has been associated with a global increase in occupational lung disease in workers exposed to respirable dust during the fabrication of benchtops and other ES products. In this study, the reactivity and subsequent oxidative reduction potential of freshly generated ES dusts were evaluated by (i) comparing different engineered and natural stones, (ii) comparing settled and respirable stone dust fractions and (iii) assessing the effect of ageing on the reactivity of freshly generated stone dust. An established cell-free deoxyguanosine hydroxylation assay was used to assess the potential for oxidative DNA damage. ES dust exhibited a higher relative reactivity than two of the three natural stones tested. Respirable dust fractions were found to be significantly more reactive than their corresponding settled fraction (ANOVA, p < 0.05) across all stone types and samples. However, settled dust still displayed high relative reactivity. The lower reactivity of the settled dust was not due to decay in reactivity of the respirable dust when it settled but rather a result of the admixture of larger nonrespirable particles. No significant change in respirable dust reactivity was observed for three ES samples over a 21-day time period, whereas a significant decrease in reactivity was observed in the natural stone studied. This study has practical implications for dust control and housekeeping in industry, risk assessment and hazard management.

Characterization of deposited dust and its respirable fractions in underground coal mines: Implications for oxidative potential-driving species and source apportionment

Oxidative potential (OP) is considered to be an efficient indicator of particulate matter (PM) to induce oxidative stress in the lungs and is increasingly considered to be a relevant health metric. In this study, two complementary OP assays were deployed, including dithiothreitol (DTT) and ascorbic acid (AA) assays, to investigate the potential toxicity (as generators of oxidative stress) of respirable fractions (DD4, < 4 μm) of deposited dust (DD500, < 500 μm) in underground low-S and low-pyrite coal mines in Henan Province, Central China. The OPDTT of DD4 is higher than that reported for other types of atmospheric PM, whereas the OPAA of DD4 is similar and/or slightly higher. Cross-correlation and multilinear regression analyses are applied using datasets of major mineral and geochemical patterns in the DD4 samples and the respective OP values to identify the major drivers for OP in respirable coal dust. Thereafter, the patterns of DD4 are compared with those of DD500 and the parent coals to determine the sources of OP-relevant substances. OPDTT is mainly governed by some trace elements (Sb, As, Li, B, Sr, and Pb) and minor minerals (anatase, quartz, siderite), and their synergistic effect may be one of the reasons for the high DTT consumption. For OPAA, quartz, total clay (sum of illite, kaolinite, tobelite, and clinochlore) and Ni, Cr, Co, Si, and S, play an important role in regulating the OPAA of pyrite-free DD4 samples. These OP-relevant substances have three sources: coal dust, which has a similar composition in DD4, DD500, and the parent coal (such as siderite and its associated elements); gangue dust, which does not occur in the parent coal but is widely detected in DD4 and DD500 (such as quartz, kaolinite, and relevant elements); and cement dust (from gunite galleries), which is mainly calcite- and calcite-associated elements.

Extended Investigation of Exposure to Respirable Synthetic Amorphous Silica Dust and Its Potential Impact on Non-malignant Respiratory Morbidity.

ObjectivesThe present analysis aims to study the health impact of an occupational exposure to respirable synthetic amorphous silica (SAS) dusts, based on the available data from the German study.MethodsThe effect of cumulative exposure to respirable SAS dust on respiratory morbidity were investigated in 462 exposed male workers. Multiple exposure assessments was performed anchored by a most recent measurement series. Internal regression models in addition to Monte Carlo-Multi Model were fitted.ResultsAn averaged cumulative respirable SAS dust concentration of 6.44 mg/m3-years was estimated. Internal regression models suggested a reduction of 8.11 ml (95% confidence interval: 0.49–15.73) in forced vital capacity (FVC) per 1 mg/m3-year increase of exposure. But no effect on forced expiratory volume in 1 s (FEV1) and the ratio of the parameters FEV1/FVC was observed in association with exposure to a respirable fraction of SAS. No adverse effects on the occurrence of respiratory diseases were indicated.ConclusionThis study provides no clear evidence of adverse health effects from occupational exposure to respirable SAS.SponsorEvonik Operations GmbH/Smart Materials, Cabot Corporation, Wacker Chemie AG.

Estimating cobalt exposure in respirable dust from cobalt in inhalable dust.

Cobalt is a commonly used element in metal industry. Exposure to workers occurs mainly by inhalation of cobalt-containing dust. For the evaluation of cobalt exposure, risk assessment and investigations on occupational diseases, measurements of cobalt in respirable dust are needed. Up to now, often only data for cobalt in inhalable dust are available, which is due to the earlier classification of the limit value in this fraction. Therefore, a possibility to convert cobalt concentrations mathematically from inhalable into respirable concentrations is desirable. In this study, 639 parallel measurements of cobalt concentrations in inhalable (cI(Co)) and respirable dust fractions (cR(Co)) were extracted from the non-public exposure database MEGA (Measurement data relating to workplace exposure to hazardous substances, maintained at the Institute for Occupational Safety and Health of the German Social Accident Insurance) and investigated by regression analysis. For the whole dataset regression shows high quality measures (correlation coefficient R=0.888, adjusted coefficient of determination adj. R2=0.788 - R2 is adjusted to sample size). Further description of the data is achieved by splitting the dataset according to the type of sampling ('stationary' and 'personal') and three working activity groups, 'high temperature processing', 'filling/transport/storage', and 'machining/abrasive techniques' (0.845 ≤ R≤0.876; 0.711 ≤ adj. R2 ≤ 0.762). As subgroups of 'high temperature processing' and 'machining/abrasive techniques' two further groups could be determined. These groups are called heuristic groups, since they have to be formed non-systematically by trial and error. These heuristic groups are 'welding' and 'grinding'. They are more selective on the included working activities with adj. R2 of 0.703 and 0.748 respectively. The resulting conversion functions of all groups are power functions with exponents between 0.704 and 0.794. For the estimation of cobalt in respirable dust in other studies, it is possible to use the conversion functions of the heuristic and working activity groups. Limitations of the possibility to use the conversion functions are discussed.

Proof-of-Concept for Adjusted Surface Energies and Modified Fines as a Novel Concept in Particle Engineering for DPI Formulations.

Currently marketed dry powder inhaler (DPI) medicine lacks drug delivery performance due to insufficient powder dispersion. In carrier-based blends, incomplete drug detachment is typically attributed to excessive adhesion forces between carrier and drug particles. Adding force control agents (FCA) is known to increase drug detachment. Several researchers accounted this effect to a decrease in carrier surface energy (SE). In turn, an increase in SE should impede drug detachment. In this proof-of-concept study, we investigated the influence of the SE of the carrier material in binary blends by intentionally inverting the FCA approach. We increased SEs by dry particle coating utilising high-shear mixing, which resulted in decreased respirable fractions of the respective blends. Thus, we confirmed the SE of the carrier influences drug delivery and should be considered in formulation approaches. Complementing engineering techniques on the carrier level, we evaluated a method to modify the SE of extrinsic fines in ternary powder blends for inhalation. By the co-milling of fine lactose and an additive, we tailored the SE and hence the adhesiveness of additional fine excipients. Thus, the extent and the strength of drug–fines agglomerates may be controllable. For ternary DPI formulations, this work highlights the potential benefits of matching the SE of both fines and drugs.

Mixed-dust pneumoconiosis in a dental technician: a multidisciplinary diagnosis case report

BackgroundIn dental laboratories, exposure to crystalline silica can occur during procedures that generate suspended mineral dusts, e.g. dispersion of mixing powders, removal of castings from molds grinding, polishing of castings and porcelain, and use of silica sand for blasting. There is also a large list of toxic agents (acrylic resins, polymeric materials, etc.) used to produce removable and fixed prostheses, but also impression materials and more. Using personal protective equipment and other aids reduces the exposure to these potentially harmful agents.Case presentationWe report the case of a 42-year-old male dental technician who began to suffer from a dry cough and exertional dyspnea after approximately 15 years of work. The operations he conducted for his job resulted in the generation of crystalline silica, aluminum, chromium and titanium dust. The worker did not regularly wear personal protective equipment and some of the above operations were not carried out in closed circuit systems. The Chest X-ray showed diffused micronodules in the pulmonary interstitium of the upper-middle lobes, bilaterally, and a modest left basal pleural effusion. Simple spirometry showed small airway obstruction in its initial stage. High Resolution Computerized Tomography of the chest showed bilateral micronodulation of a miliariform type, with greater profusion to the upper lobes, also present in the visceral pleura, bilaterally. Histological examination showed aggregates of pigment-laden macrophages forming perivascular macules or arranged in a radial pattern around a core of sclerohyalinosis. Scanning Electron Microscopy and Energy Dispersive Spectrometry revealed several mineral particles, typically characterized by the presence of crystalline silica and metal aggregates. The environmental concentrations of total dust and its respirable fraction were all lower than the relative TLV-TWA—ACGIH, yet not negligible.ConclusionsThe above findings and a multidisciplinary assessment led to the diagnosis of mixed dust pneumoconiosis s/q with 2/2 profusion of occupational origin. This diagnosis in a dental technician was supported for the first time in literature by environmental exposure analysis.

A preliminary assessment of microplastics in indoor dust of a developing country in South Asia.

Microplastics (MPs) pollution is an emerging global environmental concern. Considering the high fraction of time people spend indoors, the human population can be directly exposed to this contamination through indoor dust. This preliminary study evaluates MPs' abundance and human health risk assessment in the deposited indoor dust. A total of forty dust samples (n = 20) were collected from homes in two different cities (Pakistan) in steel mesh pouches using the vacuum cleaner. The identification and quantification of MPs were conducted with a stereo microscope, whereas the qualitative assessment was performed with Fourier transform infrared spectroscopy (FTIR). The US EPA parameters to calculate the human health risk assessment were used to determine MPs' risk per-day/month/year. Overall, microfibers were the dominant category, followed by microfilms, micro-fragments, and nurdles. The chemical categorization of MPs was revealed as polyester, polyethylene, copolymers of polypropylene, and polyurethane. In Lahore, an average abundance of 241.45 (items/m2) MPs were observed compared to Sahiwal, with 162.1 (items/m2). More than 90% of the identified MPs were microfibers, with higher detection frequency and abundance inLahorethan Sahiwal. The human health risk assessment revealed high exposure risk because of indoor MPs. Moreover, toddlers were more vulnerable as compared to adults at both low and high exposure risk scenarios. There is an imminent need to conduct in-depth risk assessment focusing on the respirable fraction of MPs.

Real-Time Emission and Exposure Measurements of Multi-walled Carbon Nanotubes during Production, Power Sawing, and Testing of Epoxy-Based Nanocomposites.

ObjectivesThe use of manufactured nanomaterials is increasing globally. Although multi-walled carbon nanotubes (CNTs) are used in a wide range of applications, only limited data are available on emissions and exposures during CNT composite production. No exposure data using portable aethalometers in the personal breathing zone (PBZ) to monitor occupational exposure to CNTs have yet been published. The aim of this study was to characterize emissions of and exposures to CNTs during CNT composite production, sawing, and shear testing. We also investigated whether real-time aethalometer measurements of equivalent black carbon (eBC) could be used as a proxy filter sampling of elemental carbon (EC). The presence of CNTs as surface contamination in the production facility was monitored since this could contribute to airborne exposure.MethodsDuring CNT composite production in an industrial setting including both chemical and manufacturing laboratories, different work tasks (WTs) were studied with a combination of direct-reading instruments (aethalometer, aerodynamic particle sizer, condensation particle counter) and filter-based methods. Measurements were performed to monitor concentrations in the emission zone (EZ), PBZ, and background zone. The filter samples were analysed for EC and fibre concentration of CNTs using scanning electron microscopy (SEM). Additionally, surfaces in the facility were tape sampled for monitoring of CNT contamination, and analysed with SEM.ResultsClear eBC peaks were observed in the PBZ during several WTs, most clearly during open handling of CNT powder. Power sawing emitted the highest particle number concentration in the EZ of both nanoparticles and coarse particles, but no individual airborne CNTs, agglomerates, or aggregates were detected. Airborne CNTs were identified, for example, in a filter sample collected in the PBZ of a worker during mixing of CNT epoxy. The airborne CNT particles were large agglomerates which looked like porous balls in the SEM images. Significant EC exposures were found in the inhalable fraction while all respirable fractions of EC were below detection. The highest inhalable EC concentrations were detected during the composite production. No significant correlation was found between inhalable EC and eBC, most likely due to losses of large EC containing particles in the sampling lines and inside the eBC monitor. In total, 39 tape samples were collected. Surface contamination of CNTs was detected on eight surfaces in the chemical and manufacturing laboratories, mainly in the near-field zone. Elongated CNT-like features were detected in the sawdust after sawing of CNT composite.ConclusionsCharacterization of a workplace producing CNT composite showed that open handling of the CNT powder during weighing and mixing of CNT powder material generated the highest particle emissions and exposures. The portable direct-reading aethalometer provided time-resolved eBC exposure data with complementary information to time-integrated EC filter samples by linking peak exposures to specific WTs. Based on the results it was not possible to conclude that eBC is a good proxy of EC. Surface contamination of CNTs was detected on several surfaces in the near-field zone in the facility. This contamination could potentially be resuspended into the workplace air, and may cause secondary inhalation exposure.

Oxygen consumption and acid secretion in isolated gas gland cells of the European eel Anguilla anguilla

Swimbladder gas gland cells are known to produce lactic acid required for the acidification of swimbladder blood and decreasing the oxygen carrying capacity of swimbladder blood, i.e., the onset of the Root effect. Gas gland cells have also been shown to metabolize glucose via the pentose phosphate shunt, but the role of the pentose phosphate shunt for acid secretion has not yet been evaluated. Similarly, aerobic metabolism of gas gland cells has been largely neglected so far. In the present study, we therefore simultaneously assessed the role of glycolysis and of the pentose phosphate shunt for acid secretion and recorded oxygen consumption of isolated swimbladder gas gland cells of the European eel. Presence of glucose was essential for acid secretion, and at glucose concentrations of about 1.5 mmol l−1 acid secretion of gas gland cells reached a maximum, indicating that glucose concentrations in swimbladder blood should not be limiting acid production and secretion under physiological conditions. The data revealed that most of the acid was produced in the glycolytic pathway, but a significant fraction was also contributed by the pentose phosphate shunt. Addition of glucose to gas gland cells incubated in a glucose-free medium resulted in a reduction of oxygen uptake. Inhibition of mitochondrial respiration significantly reduced oxygen consumption, but a fraction of mitochondria-independent respiration remained in presence of rotenone and antimycin A. In the presence of glucose, application of either iodo-acetate inhibiting glycolysis or 6-AN inhibiting the pentose phosphate shunt did not significantly affect oxygen uptake, indicating an independent regulation of oxidative phosphorylation and of acid production. Inhibition of the muscarinic acetylcholine receptor caused a slight elevation in acid secretion, while forskolin caused a concentration-dependent reduction in acid secretion, indicating muscarinic and c-AMP-dependent control of acid secretion in gas gland cells.

Comprehensive characterization of firing byproducts generated from small arms firing of lead-free frangible ammunition

Following the introduction of lead-free frangible ammunition in United States Air Force small arms firing ranges, Combat Arms instructors have routinely reported experiencing adverse health symptoms during live fire training exercises, including sore throat, cough, and headache. Previous studies have found that these symptoms occur despite occupational exposure limits not being exceeded. To better characterize the potential source and mechanisms for health symptoms, a comprehensive characterization of the physicochemical properties of gases and aerosols emitted during the firing of the M9 pistol and M4 rifle using lead-free frangible ammunition was completed. Weapons were fired within a sealed chamber using a remote firing mechanism. A suite of direct-reading instruments and collection-based analytical methods were used to determine the composition of the emissions. Emissions were dominated by carbon monoxide and ultrafine particles. Other prevalent gases included carbon dioxide, ammonia, formaldehyde, hydrogen cyanide, and nitric oxide when measured using Fourier-transform infrared spectroscopy. An electrical, low-pressure impactor showed that, on average, the count median diameter immediately after firing was 36 ± 4 nm (n = 10 rounds) and 32 ± 3 nm (n = 14 rounds) for the M9 pistol and M4 rifle, respectively. Analytical methods were used to determine that emitted particles were primarily composed of soot, copper, and potassium, with trace amounts of calcium, silicon, sodium, sulfur, and zinc. Results from this research confirm prior work and expand upon the characterization of emissions generated from firing lead-free frangible ammunition. By employing multiple methods to measure and analyze data we were able to quantify both total and respirable particle fractions and determine particle morphology and composition. Characterization of the emissions provides insight into potential exposure risks that may lead to the development of adverse health symptoms allowing for the development of strategies for risk mitigation.

Bridging the gaps between particulate backscattering measurements and modeled particulate organic carbon in the ocean

Abstract. Oceanic particulate organic carbon (POC) is a small but dynamic component of the global carbon cycle. Biogeochemical models historically focused on reproducing the sinking flux of POC driven by large fast-sinking particles (LPOC). However, suspended and slow-sinking particles (SPOC, here &lt; 100 µm) dominate the total POC (TPOC) stock, support a large fraction of microbial respiration, and can make sizable contributions to vertical fluxes. Recent developments in the parameterization of POC reactivity in PISCES (Pelagic Interactions Scheme for Carbon and Ecosystem Studies model; PISCESv2_RC) have improved its ability to capture POC dynamics. Here we evaluated this model by matching a global 3D simulation and 1D simulations at 50 different locations with observations made from biogeochemical (BGC-) Argo floats and satellites. Our evaluation covers globally representative biomes between 0 and 1000 m depth and relies on (1) a refined scheme for converting particulate backscattering at 700 nm (bbp700) to POC, based on biome-dependent POC / bbp700 ratios in the surface layer that decrease to an asymptotic value at depth; (2) a novel approach for matching annual time series of BGC-Argo vertical profiles to PISCES 1D simulations forced by pre-computed vertical mixing fields; and (3) a critical evaluation of the correspondence between in situ measurements of POC fractions, PISCES model tracers, and SPOC and LPOC estimated from high vertical resolution bbp700 profiles through a separation of the baseline and spike signals. We show that PISCES captures the major features of SPOC and LPOC across a range of spatiotemporal scales, from highly resolved profile time series to biome-aggregated climatological profiles. Model–observation agreement is usually better in the epipelagic (0–200 m) than in the mesopelagic (200–1000 m), with SPOC showing overall higher spatiotemporal correlation and smaller deviation (typically within a factor of 1.5). Still, annual mean LPOC stocks estimated from PISCES and BGC-Argo are highly correlated across biomes, especially in the epipelagic (r=0.78; n=50). Estimates of the SPOC / TPOC fraction converge around a median of 85 % (range 66 %–92 %) globally. Distinct patterns of model–observations misfits are found in subpolar and subtropical gyres, pointing to the need to better resolve the interplay between sinking, remineralization, and SPOC–LPOC interconversion in PISCES. Our analysis also indicates that a widely used satellite algorithm overestimates POC severalfold at high latitudes during the winter. The approaches proposed here can help constrain the stocks, and ultimately budgets, of oceanic POC.

Study of silver aerosol source term at different specific internal energy input from HE detonation devices

Radioactive aerosols harmful to humans are often produced in nuclear accidents, and their source term characteristics (total volume and particle size distribution) and dispersion patterns have important implications for accident response and hazard assessment. However, experimental studies of radioactive aerosols cannot be directly conducted in open space due to the hazardous nature of radioactive aerosols. In this study, silver was used instead of plutonium to study the aerosol source term under different specific internal energy inputs (SIEI) to simulate a low order explosion in an accident. Results show that aerosol release fraction (ARF) and respirable release fraction (RRF) of silver increase linearly with SIEI first, then varies in a range of 8% ~ 19%, with a turning point at SIEI of 1.4 MJ/kg. Analysis suggests an increase of difference between ARF and RRF with respect to SIEI. The size distribution of silver aerosol around 10 µm is influenced by SIEI significantly, which could be possibly attributed to the interactions between silver aerosol and ambient aerosol (solid HE products or rust). Comparison between the source term of silver and plutonium suggests that silver is a good surrogate of plutonium in studying aerosol for SIEI of MJ/kg level.

Chemistry and particle size distribution of respirable coal dust in underground mines in Central Eastern Europe

Despite international efforts to limit worker exposure to coal dust, it continues to impact the health of thousands of miners across Europe. Airborne coal dust has been studied to improve risk models and its control to protect workers. Particle size distribution analyses shows that using spraying systems to suppress airborne dusts can reduce particulate matter concentrations and that coals with higher ash yields produce finer dust. There are marked chemical differences between parent coals and relatively coarse deposited dusts (up to 500 µm, DD500). Enrichments in Ca, K, Ba, Se, Pb, Cr, Mo, Ni and especially As, Sn, Cu, Zn and Sb in the finest respirable dust fractions could originate from: (i) mechanical machinery wear; (ii) variations in coal mineralogy; (iii) coal fly ash used in shotcrete, and carbonates used to reduce the risk of explosions. Unusual enrichments in Ca in mine dusts are attributed to the use of such concrete, and elevated K to raised levels of phyllosilicate mineral matter. Sulphur concentrations are higher in the parent coal than in the DD500, probably due to relatively lower levels of organic matter. Mass concentrations of all elements observed in this study remained below occupational exposure limits.