PM Metal Research Articles

Associations between PM2.5 metal components and QT interval length

Background/Aim: Several studies have found associations between increases in QT interval length, a marker of cardiac electrical instability, and short-term fine particulate matter (PM2.5). To our knowledge, this is the first study to examine the association between specific PM metal components and QT interval length. Methods: We measured heart-rate corrected QT interval (QTc) duration among 630 participants in the Normative Aging Cohort (NAS) based in Eastern Massachusetts between 2000 to 2012. We utilized time-varying linear mixed-effects regressions with a random intercept to analyze associations between QTc interval and moving averages (0 to 7-day moving averages) of 24-hour mean concentrations of PM metal components (vanadium, nickel, copper, zinc and lead) measured at the Harvard Supersite monitoring station. Models were adjusted for daily PM2.5 mass estimated at a 1 km x 1 km grid cell from a previously validated prediction model and other covariates. Bayesian kernel machine regression (BKMR) was utilized to assess the overall effect of the PM components and the exposure-dose response curves. Results: We found consistent results with higher lead (Pb) associated with significant higher QTc intervals for both the multi-pollutant and the two pollutant (PM2.5 and a PM component) models across the moving averages. The greatest effect of lead on QTc interval was detected for the 4-day moving average lead exposure. In the multi-pollutant model, each 2.72 ng/m3 increase in daily lead levels for a 4-day moving average was associated with an 8.77 ms (95% CI: 4.25,13.29) increase in QTc interval. In the two-pollutant models with PM2.5 mass and lead, each 2.72 ng/m3 increase in daily lead levels for a 4-day moving average was associated with a 9.19 ms (95% CI: 5.09,13.30) increase in QTc interval. Conclusions: Our findings suggest that metals contained in PM2.5 are associated with acute changes (0 to 7-day moving averages) in ventricular repolarization.

A cohort study on long-term exposure to air pollution and incidence of liver cirrhosis.

We used an administrative cohort established from the 2001 census. We included all adults of 30 years of age or older who were free of cirrhosis, resulting in a study population of over 1.2 million subjects. Follow-up of the subjects ended on 31 December 2015. We ascertained incident cases of cirrhosis from regional mortality and hospital discharge registries using a validated algorithm. We assessed exposure of the subjects to PM10, PM coarse, PM2.5, PM2.5 absorbance, NO2, NOx, and PM metal components at their residential address using Land Use Regression models. We used Cox regression models, adjusted for relevant covariates, to estimate the association between air pollution exposure and cirrhosis incidence. We observed 10,111 incident cases of cirrhosis, with a crude incidence rate of 67 × 100,000 person-years. Long-term exposure to all pollutants tested was significantly associated with cirrhosis, e.g., PM10 (hazard ratios [HR], 1.05; 95% confidence interval [CI], 1.01-1.09, per 10 µg/m3 increments), PM coarse (HR, 1.11; 95% CI, 1.05-1.17, per 10 µg/m3 increments), PM2.5 (HR, 1.08; 95% CI, 1.03-1.13, per 5 µg/m3 increments), and NO2 (HR, 1.03; 95% CI, 1.02-1.05, per 10 µg/m3 increments). The associations were robust in secondary analyses. Our findings suggest a possible contribution of air pollution to the development of cirrhosis.

Desulfurization using limestone during sludge incineration in a fluidized bed furnace: Increased risk of particulate matter and heavy metal emissions

Incineration of sludge can be an effective method to minimise waste whilst producing useful heat. However, incineration can cause secondary pollution issues due to the emission of SO2, therefore a set of experiments of sludge incineration in a bubble bed furnace were conducted with limestone addition to study desulfurization of sludge incineration flue gas. As expected, over 93% emission of SO2 was reduced with limestone addition, and that of CO and NOx were increased and decreased respectively when the fuel feeding rate raised. The distribution of fly ash was also increased by raising the fuel feeding rate due to increasing fragmentation of the ash. However, distributions of PM2.5 and heavy metals in submicron particles have dramatically increased with limestone desulfurization. The mechanism was revealed by SEM and EDS statistical analysis, indicating that the reaction between aluminosilicate and calcium made particles agglomerate and eutectic mixtures form, these larger ash particles were found to divide between collection as cyclone ash and fragmentation into finer particles that bypassed the cyclone. Those fine particles provided more surface area for heavy metal condensation. Furthermore, it was found that the reaction mechanism for semi-volatile metals involved them being released from the sludge and forming PM1 particles due to the vaporization-condensation mechanism, leading to higher emission of PM1 and distribution of heavy metals in PM1. Thus, it should be considered that there may actually be higher emission risks of PM and heavy metal emissions when aiming to desulfurize a flue gas using Ca-based minerals in certain circumstances.

Mechanical Behavior of Polycrystalline Rhenium under 3-Points Bending at a Low Homological Temperature

Mechanical behaviour of polycrystalline rhenium under 3-points bending at such low homological temperature as room is discussed. Two metallurgical technologies (electron beam melting and powder metallurgy) were used for the samples preparation. Fine-grained samples (PM metal) exhibit some plasticity prior the failure, while coarse-grained ones (EBM metal) behave like a brittle solid. The intergranular fracture is the fracture mode of rhenium in both cases. Basal slip and prismatic slip of dislocations are not active in rhenium at low homological temperature, but the grain boundary sliding occurs under these conditions. Therefore, polycrystalline rhenium cannot be machined at room temperature despite the growth of grain boundary cracks are braked in the samples due to grain boundary sliding.

Characterization of metals in PM1 and PM10 and health risk evaluation at an urban site in the western Mediterranean

PM1 and PM10 samples collected in the urban center of Elche during two years were analyzed by Energy Dispersive X-Ray Fluorescence in order to determine the concentrations of the following metals: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Ba. The influence of traffic and Saharan dust intrusions on PM levels and metal content was studied in this work. The results indicate that the coarse fraction was affected more by variations in traffic intensity than the submicron fraction. The concentrations of Ca, commonly used as a tracer of road dust, showed the highest decreases during the weekends due to the reduction in traffic-induced resuspension. In contrast, Saharan events had a greater impact on the levels of other metals such as Ti and Fe, significantly affecting their seasonal variability. High concentrations of V and Ni compared with the values found at larger urban areas were observed. This could be attributed to a significant contribution from soils, Saharan dust and even ship emissions. Enrichment factors calculated using Ti as a reference element indicate that Zn and Cu are predominantly emitted by anthropogenic activities. In fact, Saharan dust intrusions had a minor influence on the average concentrations of these metals. Non-carcinogenic health hazards associated with exposure to airborne metals were lower than the safety threshold (hazard quotient < 1). Carcinogenic risks for Cr (VI) and Ni were between 10−6 and 10−4 and, therefore, within the range considered acceptable by the US EPA.

Air pollution, oxidative stress, and exacerbation of autoimmune diseases.

A number of epidemiological studies have shown a strong association between exposure to ambient airborne particulate matter (PM 2.5, PM < 1.0) and lung or cardiovascular diseases characterised by high mortality and morbidity. However, much less is known about the role of air pollution in the pathogenesis of autoimmune diseases, which constitutes a significant problem in modern society.This paper summarises the state of current research regarding the influence of PM on the development and/or progression of autoimmune diseases. A brief review of the great body of research concerning pathogenesis of autoimmune disorders is presented. Then, the scope of our review is narrowed to the research related to the impact of particulate matter on oxidative and nitrosative stress, as well as exacerbation of chronic inflammation, because they can contribute to the development of autoimmune diseases. Moreover, we discuss the impact of various components of PM (metal, organic compounds) on PM toxicity and the ability to generate oxidants.

Role of microRNA-4516 involved autophagy associated with exposure to fine particulate matter.

Metals are vital toxic components of fine particulate matter (PM2.5). Cellular responses to exposure to PM2.5 or PM metal components remain unknown. Post-transcriptional profiling and subsequent cell- and individual-based assays implied that the metal ion-binding miR-4516/RPL37/autophagy pathway could play a critical role in cellular responses to PM2.5 and PM metal stresses. miR-4516 was up-regulated in A549 cells exposed to PM2.5 and in the serum of individuals living in a city with moderate air pollution. The expression levels of the miR-4516 target genes, namely, RPL37 and UBA52, were involved in ribosome function and inhibited by exposure to PM2.5 and PM metal components. Autophagy in A549 cells was induced by PM2.5 exposure as a response to decreased RPL37 expression. Moreover, enhanced miR-4516 expression was positively correlated with the augmentation of the internal burden of aluminum and lead in individuals living in a city with moderate air pollution. Hereby, the miR-4516/RPL37/autophagy pathway may represent a novel mechanism that mediates responses to PM metal components.

Variability of levels and composition of PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; and PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; in the Barcelona metro system

Abstract. From an environmental perspective, the underground metro system is one of the cleanest forms of public transportation in urban agglomerations. Current studies report contradicting results regarding air quality in the metro systems: whereas some reveal poor air quality, others report PM levels which are lower or of the same order of magnitude than those measured in traffic sites above ground level. The present work assesses summer and winter indoor air quality and passenger exposure in the Barcelona metro, focusing on PM levels and their metal contents. In addition, the impact on indoor air quality of platform screen door systems (automated systems consisting of closed rail track and platforms) is evaluated, to determine whether these systems reduce passenger exposure to PM when compared with conventional systems (open tracks and platforms). In the Barcelona metro PM levels inside the trains in summer are amongst the lowest reported for worldwide metro systems (11–32 μg m−3 PM2.5). This is most likely due to the air conditioning system working in all carriages of the Barcelona metro during the whole year. Levels were considerably higher on the platforms, reaching mean levels of 46 and 125 μg m3 in the new (L9) and old (L3) lines, respectively. PM10 data are also reported in the present study, but comparison with other metro systems is difficult due to the scarcity of data compared with PM2.5. Results showed distinct PM daily cycles, with a drastic increase from 06:00 to 07:00 a.m., a diurnal maximum from 07:00 to 10:00 p.m., and marked decrease between 10:00 p.m. and 05:00 a.m. The elements with the highest enrichment were those associated with wheel or brake abrasion products (Ba, Fe, Cu, Mn, Cr, Sb, As, Mo, Co, Sr, among others). Laminar hematite (Fe2O3) was the dominant particle type, being mainly originated by mechanical abrasion of the rail track and wheels. Regarding passenger exposure to PM, the contribution of commuting by metro was estimated to account for around 10% of the daily exposure. However, this contribution may be one order of magnitude higher when specific matals are considered. Finally, we conclude that the implementation of platform screen door systems results in reductions of both PM levels and metal concentrations. In addition an advanced optimized ventilation system gave even a much higher efficiency in reducing exposure to PM of metro commuters. Combining these two features PM exposure levels in the platforms may be reduced down by a factor of 7 with respect the old subway lines in Barcelona.

A time-series study of the health effects of water-soluble and total-extractable metal content of airborne particulate matter

Objectives:To assess whether adverse acute cardiopulmonary health outcomes are associated with concentration of trace metals in airborne particulate matter.Methods:Daily PM10 and PM2.5 were collected for 1 year in Edinburgh, UK,...

Experimental determination of Young's modulus in PM metal matrices used in diamond impregnated tools for cutting hard materials

Experimental determination of Young's moduli of sintered metal–powder mixtures was carried out with results comparison through the use of a resonant frequency technique (dynamic excitation methodology) and an evaluation of the elastic stress–strain ratio in monotonic tensile loading regime. The materials used in this study consist of sintered bodies obtained from several metallic powders employed in the production of powder metallurgy metal composites used in diamond impregnated tools for cutting hard materials (such as stone cutting). The values of Young's modulus determined experimentally are also analysed and compared with a theoretical estimation carried out considering the chemical composition of each material and applying a simple rule of mixtures. The dynamic excitation is assumed to be the simplest experimental procedure, enabling accurate and reproducible measurements. On the other hand, the microstructure of the sintered bodies seems to influence the values of Young's modulus measured experimentally.

Polyphase sintering and properties of metal matrix composites

Examples of Fe–P, Fe–B polyphase sintered PM metal matrix composites have been considered. Microstructure and phase constitution of sinters have been tested. A special attention has been paid to Fe–Co–B cermets, which are the new PM metal matrix composites. The cermets were prepared from iron, cobalt, copper and boron powders mixture of different volume parts of these elements. Green compacts were sintered in different temperature and time. Such selection of sinters chemical constituents and sintering parameters made possible to carry out the sintering in two option in a solid phase, and with the participation of a liquid phase. The cermets produced were subjected to: metallographic tests, X-ray analysis, microanalysis, examination of hardness and of microhardness, as well as of wear tests in the process of sliding dry friction. Dilatometer analysis was used to control the basic phenomena taking place during polyphase sintering of investigated system Fe–Co–B. Cermets contain two phases: hard grains of iron–cobalt boride (FeCo) 2B, or iron–copper boride (FeCu) 2B (1800 HV) represents the reinforcement and a relatively soft and plastic eutectic mixture (FeCo) 2B–(Fe–Co) or (FeCu) 2B–(Fe–Co) (400–500 HV) been a matrix. The cermets chemical composition and sintering process parameters strongly affect the sintering mechanism and kinetics as well as cermets structure and properties. High hardness and resistance to wear of cermets were proved.

Self-energy corrections in an antiferromagnet: Interplay of classical and quantum effects on quasiparticle dispersion

Self-energy corrections due to fermion-magnon interaction are studied in the antiferromagnetic state of the $t-t'-t''$ Hubbard model within the rainbow (noncrossing) approximation in the full $U$ range from weak to strong coupling. The role of classical (mean-field) features of fermion and magnon dispersion, associated with finite $U,t',t''$, are examined on quantum corrections to quasiparticle energy, weight, one-particle density of states etc. A finite-$U$ induced classical dispersion term, absent in the $t-J$ model, is found to play an important role in suppressing the quasiparticle weight for states near ${\bf k}=(0,0)$, as seen in cuprates. For intermediate $U$, the renormalized AF band gap is found to be nearly half of the classical value, and the weak coupling limit is quite non-trivial due to strongly suppressed magnon amplitude. For finite $t'$, the renormalized AF band gap is shown to vanish at a critical interaction strength $U_c$, yielding a spin fluctuation driven first-order AF insulator - PM metal transition. Quasiparticle dispersion evaluated with the same set of Hubbard model cuprate parameters, as obtained from a recent magnon spectrum fit, provides excellent agreement with ARPES data for $\rm Sr_2 Cu O_2 Cl_2 $.

Size distribution and diurnal characteristics of particle-bound metals in source and receptor sites of the Los Angeles Basin

Measurement of daily size-fractionated ambient PM 10 mass, metals, inorganic ions (nitrate and sulfate) and elemental and organic carbon were conducted at source (Downey) and receptor (Riverside) sites within the Los Angeles Basin. In addition to 24-h concentration measurements, the diurnal patterns of the trace element and metal content of fine (0–2.5 μm) and coarse (2.5–10 μm) PM were studied by determining coarse and fine PM metal concentrations during four time intervals of the day. The main source of crustal metals (e.g., Al, Si, K, Ca, Fe and Ti) can be attributed to the re-suspension of dust at both source and receptor sites. All the crustals are predominantly present in supermicron particles. At Downey, potentially toxic metals (e.g., Pb, Sn, Ni, Cr, V, and Ba) are predominantly partitioned (70–85%, by mass) in the submicron particles. Pb, Sn and Ba have been traced to vehicular emissions from nearby freeways, whereas Ni and Cr have been attributed to emissions from powerplants and oil refineries upwind in Long Beach. Riverside, adjacent to Southern California deserts, exhibits coarser distributions for almost all particle-bound metals as compared to Downey. Fine PM metal concentrations in Riverside seem to be a combination of few local emissions and those transported from urban Los Angeles. The majority of metals associated with fine particles are in much lower concentrations at Riverside compared to Downey. Diurnal patterns of metals are different in coarse and fine PM modes in each location. Coarse PM metal concentration trends are governed by variations in the wind speeds in each location, whereas the diurnal trends in the fine PM metal concentrations are found to be a function both of the prevailing meteorological conditions and their upwind sources.

Materials and processing technology for PM metal matrix composites (MMC) : A. Feest, (AEA Industrial Technology, Harwell, England)

Materials and processing technology for PM metal matrix composites (MMC) : A. Feest, (AEA Industrial Technology, Harwell, England)

Review of PM metal matrix composites

Review of PM metal matrix composites