Organic Dust Research Articles

Occupational Exposures to Organic Dust in Irish Bakeries and a Pizzeria Restaurant.

For decades, occupational exposure to flour dust has been linked to a range of respiratory diseases, including occupational asthma, thought to result from exposure to fungi present in the flour. Antifungal resistance is of increasing prevalence in clinical settings, and the role of occupational and environmental exposures, particularly for specific fungal species, is of concern. Occupational exposure to flour dust can occur in a range of occupational settings, however, few studies have focused on restaurant workers. The objective of this study was to measure occupational exposure to flour and microbial contamination, including azole resistance screening, in two small commercial bakeries and in a pizzeria. Personal full shift inhalable dust measurements were collected from workers, and were analyzed for inhalable dust and fungi, bacteria, azole resistance, and mycotoxins. Samples of settled dust were collected, and electrostatic dust cloths (EDC) were deployed and analyzed for microbial contamination, including azole resistance screening, and mycotoxins. Geometric mean exposures of 6.5 mg m−3 were calculated for inhalable dust, however, exposures of up to 18.30 mg m−3 were measured—70% of personal exposure measurements exceeded the occupational exposure limit for flour dust of 1.0 mg m−3. The air and EDC fungal counts were similar to those reported in previous studies for similar occupational environments. The fungi were dominated by Penicillium genera, however Aspergillus genera, including Fumigati and Flavi sections, were observed using culture-based methods, and the Fumigati section was also observed by molecular tools. Both Aspergillus sections were identified on the azole resistance screening. Mycotoxins were also detected in the settled dust samples, dominated by deoxynivalenol (DON). The role of environmental exposure in both the development of antimicrobial resistance and the total mycotoxin body burden is a growing concern; therefore, the presence of azole-resistant fungi and mycotoxin contamination, although low in magnitude, is of concern and warrants further investigation.

Yearly changes of the sulfate-nitrate-ammonium aerosols and the relationship with their precursors from 1999 to 2016 in Beijing

The change in particulate matter (PM)2.5 composition in relation to precursors over recent decades has not been elucidated clearly in Beijing. Using ground-based measurements from the literature, this study investigated the yearly time series of PM2.5 and its chemical composition over Beijing from 1999 to 2016 to identify the driving forces underlying these changes. The PM2.5 concentration declined slightly, due to the organic carbon, elemental carbon, and dust rather than to either sulfate-nitrate-ammonium (SNA) aerosols. Before 2013, the trend of SNA aerosols was opposite to that of PM2.5; however, subsequently, SNA aerosols have represented the major contribution to the reduction of PM2.5, coinciding with a large decline of regional precursor gases. The yearly time series of SNA aerosols can be explained better by regional precursor gases than by local ones. Generally, precursor gases emissions over the region of North China Plain can be controlled if Beijing's air quality is to be improved.

Risk of respiratory hospital admission associated with modelled concentrations of Aspergillus fumigatus from composting facilities in England

Bioaerosols have been associated with adverse respiratory-related health effects and are emitted in elevated concentrations from composting facilities. We used modelled Aspergillus fumigatus concentrations, a good indicator for bioaerosol emissions, to assess associations with respiratory-related hospital admissions. Mean daily Aspergillus fumigatus concentrations were estimated for each composting site for first full year of permit issue from 2005 onwards to 2014 for Census Output Areas (COAs) within 4 km of 76 composting facilities in England, as previously described (Williams et al., 2019). We fitted a hierarchical generalized mixed model to examine the risk of hospital admission with a primary diagnosis of (i) any respiratory condition, (ii) respiratory infections, (iii) asthma, (iv) COPD, (v) diseases due to organic dust, and (vi) Cystic Fibrosis, in relation to quartiles of Aspergillus fumigatus concentrations. Models included a random intercept for each COA to account for over-dispersion, nested within composting facility, on which a random intercept was fitted to account for clustering of the data, with adjustments for age, sex, ethnicity, deprivation, tobacco sales (smoking proxy) and traffic load (as a proxy for traffic-related air pollution). We included 249,748 respiratory-related and 3163 Cystic Fibrosis hospital admissions in 9606 COAs with a population-weighted centroid within 4 km of the 76 included composting facilities. After adjustment for confounders, no statistically significant effect was observed for any respiratory-related (Relative Risk (RR) = 0.99; 95% Confidence Interval (CI) 0.96–1.01) or for Cystic Fibrosis (RR = 1.01; 95% CI 0.56–1.83) hospital admissions for COAs in the highest quartile of exposure. Similar results were observed across all respiratory disease sub-groups. This study does not provide evidence for increased risks of respiratory-related hospitalisations for those living near composting facilities. However, given the limitations in the dispersion modelling, risks cannot be completely ruled out. Hospital admissions represent severe respiratory episodes, so further study would be needed to investigate whether bioaerosols emitted from composting facilities have impacts on less severe episodes or respiratory symptoms.

Analysis of Pulmonary Complement Protein Expression Following Organic Dust Exposure

Author(s): Ibrahim, Sarah; Sveiven, Stefanie; Nordgren, Tara | Abstract: Organic dust, as found in agricultural farm work, is ranked among the highest occupational exposure hazards by the CDC. Agricultural dust containing endotoxins, pesticides, mold, and other chemicals, contributes to increased rates of respiratory diseases among these workers. Human bronchial epithelial cells (HBEC), which line upper airways, are frequently exposed to pathogens. Understanding the role of HBEC in inflammation following dust exposure (DE) is necessary to understand the mechanisms underlying inflammatory diseases. The complement system, a nonspecific and non-adaptable defense mechanism, is composed of circulating proteins that promote inflammation by attacking the cell membranes of pathogens and recruiting immune cells that secrete mediators of inflammation. We characterized complement protein expression in DE-treated HBEC using previously generated SWATH proteomics data and Western blotting. Western blotting identified that DE treatment in HBEC mediates the release and activation of C3, while data identified via SWATH-MS proteomics indicated significant upregulation of CD59—a regulator of complement activation. These data suggest that DE-HBEC may regulate complement activation and aim to elucidate the mechanisms by which HBEC promotes the complement system, and thus induce pulmonary inflammation in the presence of organic dust.

Hypersensitivity Pneumonitis: Perspective in Diagnosis and Pathology

Hypersensitivity pneumonitis (HP) is the excessive immune response in the lung parenchyma (alveoli, terminal bronchiole, interstitium), resulting from repeated exposure to a variety of antigens. From the clinical point of view, HP can be divided into acute, subacute, or chronic forms. Only few of the exposed individuals develop HP, but workers in environments contaminated by organic dust are at a higher risk. The pathogenesis of HP is complex and still under investigation. Previous research suggests that both type III and IV hypersensitivity reactions are involved. The main treatment is the removal of antigen. Therefore, research of causative agents and pathogenesis is of outstanding importance not only for early diagnosis but also the better treatment of HP.

Cytokine gene polymorphisms in Pigeon Breeder's Disease expression.

Background:Exaggerated immunological response to repeated inhalation of organic or chemical dusts may lead to Hypersensitivity Pneumonitis among sensitized individuals. Only a few exposed individuals became ill and disease expression pattern is highly variable which suggest that genetic factors may play a role.Aim:To investigate interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-6, transforming growth factor (TGF)-ß, and IL-10 gene polymorphisms in a cohort of pigeon breeder’s disease (PBD) patients in comparison with exposed but healthy controls and the association with different patterns of disease.Methods:We evaluated 40 PBD patients and 70 exposed controls. IFN-γ, TNF-α, IL-6, TGF-ß, and IL-10 polymorphisms were determined by polymerase chain reaction–sequence specific primer amplification.Results:Polymorphism analysis of IFN-γ, TNF-α, IL-6, TGF-ß, and IL-10 genotypes and allele frequencies showed no differences between patients and controls. IFN-γ T/T genotype frequency was increased among patients with chronic presentation (RR=2.33, p=0.047) compared with those with acute/subacute presentation. Also, chronic presenting patients had an increased frequency of IFN-γ T allele (50% vs 22.5%, RR=1.76, p=0.011). No differences were found in TNF-α, IL-6, TGF-ß, and IL-10 genotypes neither allelic frequencies between both groups of patients. IL-6 C/C genotype was more frequent in patients who showed chronic evolution (RR=2.54, p=0.017), when comparing with patients with disease resolution.Conclusion:IFN-γ T/T and the IL-6 C/C genotypes seem to play a role in HP expression due to avian exposure, as their frequencies are increased in chronic presentations or in those with chronic evolution one year after the initial diagnosis, respectively. (Sarcoidosis Vasc Diffuse Lung Dis 2020; 37 (3): e2020004)

Organic dust-induced lung injury and repair: Bi-directional regulation by TNFα and IL-10

Exposure to organic dust increases chronic airway inflammatory disorders. Effective treatment strategies are lacking. It has been reported that hog barn dust extracts (HDE) induce TNFα through protein kinase C (PKC) activation and that lung inflammation is enhanced in scavenger receptor A (SRA/CD204) knockout (KO) mice following HDE. Because interleukin (IL)-10 production can limit excessive inflammation, it was hypothesized here that HDE-induced IL-10 would require CD204 to effect inflammatory responses. C57BL/6 wild-type (WT), SRA KO, and IL-10 KO mice were intranasally challenged daily for 8 days with HDE and subsequently rested for 3 days with/without recombinant IL-10 (rIL-10) treatment. Primary peritoneal macrophages (PM) and murine alveolar macrophages (MH-S cells) were treated in vitro with HDE, SRA ligand (fucoidan), rIL-10, and/or PKC isoform inhibitors. HDE induced in vivo lung IL-10 in WT, but not SRA KO mice, and similar trends were demonstrated in isolated PM from same treated mice. Lung lymphocyte aggregates and neutrophils were elevated in in vivo HDE-treated SRA and IL-10 KO mice after a 3-d recovery, and treatment during recovery with rIL-10 abrogated these responses. In vitro rIL-10 treatment reduced HDE-stimulated TNFα release in MH-S and WT PM. In SRA KO macrophages, there was reduced IL-10 and PKC zeta (ζ) activity and increased TNFα following in vitro HDE stimulation. Similarly, blocking SRA (24 hr fucoidan pre-treatment) resulted in enhanced HDE-stimulated macrophage TNFα and decreased IL-10 and PKCζ activation. PKCζ inhibitors blocked HDE-stimulated IL-10, but not TNFα. Collectively, HDE stimulates IL-10 by an SRA- and PKCζ-dependent mechanism to regulate TNFα. Enhancing resolution of dust-mediated lung inflammation through targeting IL-10 and/or SRA may represent new approaches to therapeutic interventions.

Assessment of the Level of Organic Dust and Mould Spores in the Work Environment of Baker.

Aim:This study was conducted to determine the level of fungal contamination of the air in bakeries to assess health hazards for workers.Materials and Methods:Six bakeries producing traditionally baked goods were selected for the study. After a background survey, samples of exhaled air were collected to test for fungal aerosols. The inhalable and respirable fraction in the bakery air environment was measured by the gravimetric method.Statistical Analysis Used:All data analyses were performed using Statistica software (v 8.0).Results:The mean concentration of fungi and particles in the bakeries did not exceed the recommended levels. The air in the bakeries had a low level of microbial contamination. The identified fungi included biological agents from hazard group 2.Conclusions:Proper employee training and the introduction of preventive measures (including both individual and group protection) can significantly reduce employees’ exposure and thus their occupational risk.

Effect of Industrial Dust Deposition on Photovoltaic Module Performance: Experimental Measurements in the Tropical Region

Dust particle accumulation affects outdoor photovoltaic module transmittance of solar cell glazing and thus leads to significant degradation of conversion efficiency owing to lower irradiance reaching the surface. In this study, the sensitivity of the polycrystalline silicon photovoltaic module towards industrial dust deposition was experimentally investigated under the tropical climatic condition of Arusha, Tanzania. Dust involved in the study came from fertilizer, gypsum, aggregate crusher, and coal mine industries. The experimental measurements were outdoor conducted under 720 W/m2, 800 W/m2, and 900 W/m2 solar irradiances. Results indicated that dust accumulation on the polycrystalline silicon photovoltaic module negatively affected output power as well as short-circuit current, however having no significant impact on open-circuit voltage. Maximum module efficiency loss was observed to be 64%, 42%, 30%, and 29% for coal, aggregate, gypsum, and organic fertilizer dust, respectively; hence, coal dust was the most effecting dust among the four. It was also demonstrated that PV module performance deteriorated with temperature rise owing to heat dissipation caused by dust accumulation.

Evaluating wildfire emissions projection methods in comparisons of simulated and observed air quality

Abstract. Climate warming has been implicated as a major driver of recent catastrophic wildfires worldwide but analyses of regional differences in US wildfires show that socioeconomic factors also play a large role. We previously leveraged statistical projections of annual areas burned (AAB) over the fast-growing southeastern US that include both climate and socioeconomic changes from 2011 to 2060 and developed wildfire emissions estimates over the region at 12 km × 12 km resolution to enable air quality (AQ) impact assessments for 2010 and selected future years. These estimates employed two AAB datasets, one using statistical downscaling (“statistical d-s”) and another using dynamical downscaling (“dynamical d-s”) of climate inputs from the same climate realization. This paper evaluates these wildfire emissions estimates against the U.S. National Emissions Inventory (NEI) as a benchmark in contemporary (2010) simulations with the Community Multiscale Air Quality (CMAQ) model and against network observations for ozone and particulate matter below 2.5 µm in diameter (PM2.5). We hypothesize that our emissions estimates will yield model results that meet acceptable performance criteria and are comparable to those using the NEI. The three simulations, which differ only in wildfire emissions, compare closely, with differences in ozone and PM2.5 below 1 % and 8 %, respectively, but have much larger maximum mean fractional biases (MFBs) against observations (25 % and 51 %, respectively). The largest biases for ozone are in the fire-free winter, indicating that modeling uncertainties other than wildfire emissions are mainly responsible. Statistical d-s, with the largest AAB domain-wide, is 7 % more positively biased and 4 % less negatively biased in PM2.5 on average than the other two cases, while dynamical d-s and the NEI differ only by 2 %–3 % partly because of their equally large summertime PM2.5 underpredictions. Primary species (elemental carbon and ammonium from ammonia) have good-to-acceptable results, especially for the downscaling cases, providing confidence in our emissions estimation methodology. Compensating biases in sulfate (positive) and in organic carbon and dust (negative) lead to acceptable PM2.5 performance to varying degrees (MFB between −14 % and 51 %) in all simulations. As these species are driven by secondary chemistry or non-wildfire sources, their production pathways can be fruitful avenues for CMAQ improvements. Overall, the downscaling methods match and sometimes exceed the NEI in simulating current wildfire AQ impacts, while enabling such assessments much farther into the future.

Rare occupational respiratory diseases

This paper reviews rare occupational respiratory diseases with uncommon causes. Among others, it refers to the Ardystil syndrome characterized by the occurrence of organizing pneumonia in the textile printing sprayers, as a result of inhalation of substances used in aerographic textile printing. Furthermore, secondary pulmonary alveolar proteinosis due to exposure to chemical and organic dusts was described, and so was the occurrence of the "vineyard sprayer's lung" in farm workers in Portugal. Eosinophilic bronchitis, showing a strong resemblance to bronchial asthma, was found to occur, among others, in a baker, a nurse and workers exposed to acrylates, α-amylase or welding gases. Occupational exposure to diacetyl in popcorn production workers might also create a threat to their respiratory system. A newly recognized factor that may cause bronchitis and lung diseases is the fiberglass used by workers building small boats and ships. An increased risk for respiratory ailments is observed in people employed in the textile industry, exposed to commodities or cotton dust. Even the resources used to protect different surfaces against moisture have been recognized as the causative agents of lung diseases. The rare occurrence of some occupational respiratory diseases enables a detailed analysis of the epidemiology and evaluation of the relationship between the etiologic agents and the development of the disease. This literature review highlights the fact that most respiratory diseases require a special analysis of occupational and environmental exposure. Med Pr. 2020;71(1):89-104.

Cardiovascular Risk in COPD: Deciphering the Contribution of Tobacco Smoking

The observation that COPD is an independent risk factor for cardiovascular disease (CVDs) comes from comparisons between smokers with COPD and smokers without COPD. The mechanisms that explain increased risk of CVD in patients with COPD are still unclear. The goal of this study was to assess systemic arterial stiffness (a predictor of CVD mortality) and to evaluate its determinants in a group of patients with mild to moderate COPD secondary to organic dust exposure, tobacco smoking, or both. Systemic arterial stiffness was assessed by using aortic pulse wave velocity (aPWV). Measurements were made in 142 patients with COPD and 155 healthy controlsubjects matched for age, sex, BMI, and tobacco smoking, exposed to tobacco smoking (n= 56/70 for COPD/control subjects, respectively), organic dusts (n= 44/48), or both (n= 42/37). aPWV was higher in COPD than in healthy controls in subjects exposed to tobacco smoking and to both organic dusts and tobacco smoking. By contrast, among never smokers exposed to organic dusts, patients with COPD and matched control subjects had similar aPWV. Multivariate analysis of the 142 patients with COPD (exposed to tobacco smoking and/or to organic dusts) showed that tobacco smoking was associated with high aPWV. Moreover, soluble suppression of tumorigenicity 2, a marker of major cardiovascular events, was correlated with aPWV in these patients. Analysis of an unselected group of patients with COPD with different causessuggests that: (1) COPD by itself is not sufficient to explain increased aPWV; and (2) tobacco smoking is a risk factor for elevated aPWV in COPD.

Persistent contamination of Salmonella, Campylobacter, Escherichia coli, and Staphylococcus aureus at a broiler farm in New Zealand.

Intensive poultry production due to public demand raises the risk of contamination, creating potential foodborne hazards to consumers. The prevalence and microbial load of the pathogens Campylobacter, Salmonella, Staphylococcus aureus, and Escherichia coli was determined by standard methods at the farm level. After disinfection, swab samples collected from wall crevices, drinkers, and vents were heavily contaminated, as accumulated organic matter and dust likely protected the pathogens from the disinfectants used. The annex floor also showed high microbial concentrations, suggesting the introduction of pathogens from external environments, highlighting the importance of erecting hygiene barriers at the entrance of the main shed. Therefore, pathogen control measures and proper application of disinfectants are recommended as intervention strategies. Additionally, quantitative polymerase chain reaction (qPCR) was evaluated as a quantification tool. qPCR showed limitations with samples containing low microbial counts because of the low detection limit of the method. Thus, bacterial pre-enrichment of test samples may be necessary to improve the detection of pathogens by qPCR.

Amphiregulin modulates murine lung recovery and fibroblast function following exposure to agriculture organic dust.

Exposure to agricultural bioaerosols can lead to chronic inflammatory lung diseases. Amphiregulin (AREG) can promote the lung repair process but can also lead to fibrotic remodeling. The objective of this study was to determine the role of AREG in altering recovery from environmental dust exposure in a murine in vivo model and in vitro using cultured human and murine lung fibroblasts. C57BL/6 mice were intranasally exposed to swine confinement facility dust extract (DE) or saline daily for 1 wk or allowed to recover for 3-7 days while being treated with an AREG-neutralizing antibody or recombinant AREG. Treatment with the anti-AREG antibody prevented resolution of DE exposure-induced airway influx of total cells, neutrophils, and macrophages and increased levels of TNF-α, IL-6, and CXCL1. Neutrophils and activated macrophages (CD11c+CD11bhi) persisted after recovery in lung tissues of anti-AREG-treated mice. In murine and human lung fibroblasts, DE induced the release of AREG and inflammatory cytokines. Fibroblast recellularization of primary human lung mesenchymal matrix scaffolds and wound closure was inhibited by DE and enhanced with recombinant AREG alone. AREG treatment rescued the DE-induced inhibitory fibroblast effects. AREG intranasal treatment for 3 days during recovery phase reduced repetitive DE-induced airway inflammatory cell influx and cytokine release. Collectively, these studies demonstrate that inhibition of AREG reduced, whereas AREG supplementation promoted, the airway inflammatory recovery response following environmental bioaerosol exposure, and AREG enhanced fibroblast function, suggesting that AREG could be targeted in agricultural workers repetitively exposed to organic dust environments to potentially prevent and/or reduce disease.

Occupational exposure to organic dusts and risk of developing rheumatoid arthritis: findings from a Swedish population-based case–control study

ObjectivesWe estimated the association between occupational exposures to five different organic dusts: wood, animal, paper, textile and flour dust and the risk of developing rheumatoid arthritis (RA).MethodsThis population-based case–control study...

Flame propagation and pressure characteristics of polymethyl methacrylate dust explosions in a horizontal pipe

To reveal the characteristics of flame propagation and pressure in organic dust explosions during pneumatic transportation, 30 μm polymethyl methacrylate (PMMA) dust explosions with different airflow velocities were experimentally conducted in a horizontal pipe. The results showed that dust flame transited from the luminous flame with a continuous structure to discrete flames as flame propagating. After the appearance of the discrete flames, flame propagation velocity increased sharply owing to the positive feedback coupling between combustion and expansion. With the increase of dust concentration, the average flame propagation velocity, maximum flame temperature, temperature rising rate, maximum pressure, and maximum rate of pressure rise increased and then decreased. These explosion characteristics (except for the maximum flame temperature) increased significantly with the increase of airflow velocity. When airflow velocity increased from 6.39 m/s to 13.3 m/s, the peaks of average flame propagation velocity increased from 23.9 m/s to 38.2 m/s; the peaks of maximum pressure and maximum rate of pressure rise were increased by 1.9 and 6.1 times respectively. In addition, it was found that the optimum dust concentration decreased as airflow velocity increased. Furthermore, the relationship among flame propagation, temperature, and pressure was discussed in detail.

Methanogenic Archaea: Emerging Partners in the Field of Allergic Diseases.

Archaea, which form one of four domains of life alongside Eukarya, Bacteria, and giant viruses, have long been neglected as components of the human microbiota and potential opportunistic infectious pathogens. In this review, we focus on methanogenic Archaea, which rely on hydrogen for their metabolism and growth. On one hand, methanogenic Archaea in the gut are functional associates of the fermentative digestion of dietary fibers, favoring the production of beneficial short-chain fatty acids and likely contributing to the weaning reaction during the neonatal window of opportunity. On the other hand, methanogenic Archaea trigger the activation of innate and adaptive responses and the generation of specific T and B cells in animals and humans. In mouse models, lung hypersensitivity reactions can be induced by inhaled methanogenic Archaea mimicking human professional exposure to organic dust. Changes in methanogenic Archaea of the microbiota are detected in an array of dysimmune conditions comprising inflammatory bowel disease, obesity, malnutrition, anorexia, colorectal cancer, and diverticulosis. At the subcellular level, methanogenic Archaea are activators of the TLR8-dependent NLRP3 inflammasome, modulate the release of antimicrobial peptides and drive the production of proinflammatory, Th-1, Th-2, and Th-17 cytokines. Our objective was to introduce the most recent and major pieces of evidence supporting the involvement of Archaea in the balance between health and dysimmune diseases, with a particular focus on atopic and allergic conditions.

Evaluation of Dust Concentration During Grinding Grain in Sustainable Agriculture

This work analyses the organic dust concentration during a wheat grinding process which was carried out using two types of grinders: A hammer mill and a roller mill. DustTrak II aerosol monitor was used to measure the concentration of the dust PM10 (particles with the size smaller than 10 μm), PM4.0, and PM1.0. An increase of the grain moisture to 14% resulted in the reduction in PM10 when grinding grain using the hammer mill. An inverse relationship was obtained when grain was ground using the roller mill. A smaller amount of the fraction below 0.1 mm was observed for larger diameter of the holes in the screen and smaller size of the working gap in the roller mill. For both mills, the obtained concentration of the PM10 fraction dust exceeded the acceptable level. To protect farmers health, it is necessary to use dust protection equipment or to modify the grinding technology by changing the grain moisture content and/or the grinding parameters.

Niacin, lycopodium and polyethylene powder explosibility in 20-L and 1-m3 test chambers

An experimental program has been undertaken to investigate the explosibility of selected organic dusts. The work is part of a larger research project aimed at examination of a category of combustible dusts known as marginally explosible. These are materials that appear to explode in laboratory-scale test chambers, but which may not produce appreciable overpressures and rates of pressure rise in intermediate-scale chambers. Recent work by other researchers has also demonstrated that for some materials, the reverse occurs – i.e., values of explosion parameters are higher in a 1-m3 chamber than one with a volume of 20 L. Uncertainties can therefore arise in the design of dust explosion risk reduction measures.The following materials were tested in the current work: niacin, lycopodium and polyethylene, all of which are well-known to be combustible and which cover a relatively wide range of explosion consequence severity. The concept of marginal explosibility was incorporated by testing both fine and coarse fractions of polyethylene. Experiments were conducted at Dalhousie University using the following equipment: (i) Siwek 20-L explosion chamber for determination of maximum explosion pressure (Pmax), volume-normalized maximum rate of pressure rise (KSt), and minimum explosible concentration (MEC), (ii) MIKE 3 apparatus for determination of minimum ignition energy (MIE), and (iii) BAM oven for determination of minimum ignition temperature (MIT). Testing was also conducted at Fauske & Associates, LLC using a 1-m3 explosion chamber for determination of Pmax, KSt and MEC. All equipment were calibrated against reference dusts, and relevant ASTM methodologies were followed in all tests.The explosion data followed known trends in accordance with relevant physical and chemical phenomena. For example, Pmax and KSt values for the fine sample of polyethylene were higher than those for the coarse sample because of the decrease in particle size. MEC values for all samples were comparable in both the 20-L and 1-m3 chambers. Pmax and KSt values compared favorably in the different size vessels except for the coarse polyethylene sample. In this case, KSt determined in a volume of 1 m3 was significantly higher than the value from 20-L testing. The fact that the 20-L KSt was low (23 bar m/s) does not indicate marginal explosibility of the coarse polyethylene. This sample is clearly explosible as evidenced by the measured values of MEC, MIE, MIT, and 1-m3 KSt (at both 550 and 600 ms ignition delay times).

Pollution Characteristics and Source Apportionment of Fine Particulate Matter in Autumn and Winter in Puyang, China

As one of the air pollution transmission channels around the beijing-Tianjin-Hebei region, Puyang frequently suffer from severe airpollution in autumn and winter. In order to study the characteristics and main sources of fine particulate matter during these periods, manual membrane sampling of PM2.5 was conducted at three national control sites from October 15, 2017, to January 13, 2018. Chemical composition analysis was conducted and, combined with a PMF receptor model, source analysis of the fine particles was also undertaken. The results show that the average mass concentration of PM2.5 in Puyang was 94.16 μg·m-3 in the autumn and winter of 2017, and Pushuihe station was the most polluted site. During the heating season, the three control stations all recorded the frequent occurrence of severe and serious pollution events, while the frequency of mild pollution events decreased. When heavy pollution events occurred, the concentrations of NO2 and CO increased significantly. The main components of PM2.5 were water-soluble ions (52.33%), OCEC (25.32%), and crustal elements (0.08%). The concentrations of NO3- were high while the concentrations of SO42- were low. When heavy pollution occurred, the concentrations of water-soluble ions, OC, EC, and K in PM2.5 increased significantly, while the concentrations of crustal elements decreased. During the sampling period, the conversion ratios of sulfur and nitrogen in Puyang were high and atmospheric oxidation was strong. The transformation of sulfur and nitrogen promoted the occurrence of heavy pollution. Emissions of NOx, CO, and VOCs were higher in Puyang in 2017, and the source apportionment results showed that the main sources of PM2.5 in autumn and winter were secondary inorganic salts (37%), industrial sources (16%), secondary organic aerosol (SOA, 14%), biomass combustion (12%), mobile sources (9%), coal burning (7%), and dust (4%). Secondary transformation played an important role in the development of heavy pollution events in Puyang. It is necessary to focus on the control of emissions from industrial sources, biomass combustion, moving source, and civil coal combustion.