Particle Burden Research Articles

Detection of occult lung impairment in welders by induced sputum particles and breath oxidation

We evaluated particulate matter in combined induced sputum (IS) and oxidation in exhaled breath condensate (EBC) to test whether underlying inflammatory changes are present in asymptomatic welders. Thirty welders from the Israel Defense Forces exposed to aluminum/iron (Group 1) or to cadmium/chromium/iron/lead/nickel (Group 2, N = 16) and 27 non-exposed administrators were studied. IS was recovered, particle size distribution, hydrogen peroxide and pH were measured, and exhaled breath condensate was collected. Group 2 had a higher % neutrophils than all other participants (P = 0.0001) and a higher % particles >2 microm in diameter (P = 0.0017). Percent particles and years of exposure highly correlated (P = 0.051). All welders EBC samples had higher concentrations of hydrogen peroxide than controls (P = 0.0001). pH was lower only for Group 2 (P = 0.0001). Combined IS and EBC measurements detect underlying inflammation in airways of asymptomatic welders. It emerged that airway inflammation is present in asymptomatic welders, and that the particle burden, inflammatory cells, and level of oxidative stress are a function of the type and the duration of welding. Am. J. Ind. Med. 51:503-511, 2008.

Trace gas and aerosol interactions in the fully coupled model of aerosol‐chemistry‐climate ECHAM5‐HAMMOZ: 2. Impact of heterogeneous chemistry on the global aerosol distributions

We use the ECHAM5‐HAMMOZ aerosol‐chemistry‐climate model to quantify the influence of trace gas–aerosol interactions on the regional and global distributions and optical properties of aerosols for present‐day conditions. The model includes fully interactive simulations of gas phase and aerosol chemistry including a comprehensive set of heterogeneous reactions. We find that as a whole, the heterogeneous reactions have only a small effect on the SO2 and sulfate burden because of competing effects. The uptake of SO2 on dust and sea salt decreases the SO2 concentrations while the decrease in OH (that results from the uptake of HO2, N2O5, and O3) tends to increase SO2 (because of reduced oxidation). The sulfate formed in sea salt aerosols from SO2 uptake accounts for 3.7 Tg(S) a−1 (5%) of the total sulfate production. Uptake and subsequent reaction of SO2 on mineral dust contributes to a small formation of sulfate (0.55 Tg(S) a−1, <1%), but is responsible for the coating of mineral dust particles, resulting in an extra 300 Tg a−1 of dust being transferred from the insoluble to the soluble mixed modes. The burden of dust in the insoluble modes is reduced by 44%, while the total burden is reduced by 5% as a result of enhanced wet deposition efficiency. Changes in the sulfur cycle affect the H2SO4 concentrations and the condensation of H2SO4 on black carbon. Accounting for heterogeneous reactions enhances the global mean burden of hydrophobic black carbon particles by 4%. The changes in aerosol mixing state result only in a small change in the global and annual aerosol optical depth (AOD) and absorption optical depth (ABS), but have significant implications on regional and seasonal scale. For example, in the main polluted regions of the Northern Hemisphere, AOD and ABS increase by 10–30% and up to 15%, respectively, in winter.

Modes of Wear After Semiconstrained Total Elbow Arthroplasty

Background: Osteolysis and aseptic loosening are increasingly recognized complications of total elbow arthroplasty. However, unlike the literature on total hip and knee arthroplasty, studies describing the mechanisms of these processes after total elbow arthroplasty are sparse. Methods: Semiconstrained total elbow arthroplasty components were retrieved from sixteen elbows (fourteen patients) at either revision surgery (at a mean of five years after implantation) for mechanical failure (fifteen elbows) or postmortem examination (one elbow). In all cases, the retrieved implant was the primary implant. The patterns of damage on these components were investigated with stereomicroscopy in correlation with clinical findings, serial radiographs, and histopathological observations. Results: All of the retrieved devices exhibited multiple modes of wear. Damage to the humeral and ulnar polyethylene bushings was nearly universal; twenty-seven of twenty-eight humeral bushings demonstrated asymmetrical thinning, while fifteen of sixteen ulnar bushings demonstrated elliptical plastic deformation. In addition, unintended metal-on-metal wear between bearing and nonbearing surfaces or between two nonbearing surfaces was commonly observed, typically in association with wear and deformation of the polyethylene bushings. Wear between the stem and the cement mantle was observed in most of the ulnar components. The histopathology of the periprosthetic tissues was similar in character to that observed in association with osteolysis and loosening of total hip and knee replacements, while analysis of the particulate debris revealed a preponderance of titanium alloy and polyethylene debris. Barium sulfate particles were also observed to a lesser extent. Conclusions: Multimodal wear in total elbow replacements can lead to osteolysis, aseptic loosening, and prosthetic and periprosthetic fracture necessitating revision surgery. Polyethylene wear and damage, as well as unintended metal-on-metal wear, contribute to the periprosthetic particulate burden, which is likely pathogenic in these processes.

Comparative study of pulmonary responses to nano- and submicron-sized ferric oxide in rats

Ferric oxide (Fe 2O 3) nanoparticles are of considerable interest for application in nanotechnology related fields. However, as iron being a highly redox-active transition metal, the safety of iron nanomaterials need to be further studied. In this study, the size, dose and time dependent of Fe 2O 3 nanoparticle on pulmonary and coagulation system have been studied after intratracheal instillation. The Fe 2O 3 nanoparticles with mean diameters of 22 and 280 nm, respectively, were intratracheally instilled to male Sprague Dawley rats at low (0.8 mg/kg bw) and high (20 mg/kg bw) doses. The toxic effects were monitored in the post-instilled 1, 7 and 30 days. Our results showed that the Fe 2O 3 nanoparticle exposure could induce oxidative stress in lung. Alveolar macrophage (AM) over-loading of phagocytosed nanoparticle by high dose treatment had occurred, while the non-phagocytosed particles were found entering into alveolar epithelial in day 1 after exposure. Several inflammatory reactions including inflammatory and immune cells increase, clinical pathological changes: follicular hyperplasia, protein effusion, pulmonary capillary vessel hyperaemia and alveolar lipoproteinosis in lung were observed. The sustain burden of particles in AM and epithelium cells has caused lung emphysema and pro-sign of lung fibrosis. At the post-instilled day 30, the typical coagulation parameters, prothrombin time (PT) and activated partial thromboplastin time (APTT) in blood of low dose 22 nm-Fe 2O 3 treated rats were significantly longer than the controls. We concluded that both of the two-sized Fe 2O 3 particle intratracheal exposure could induce lung injury. Comparing with the submicron-sized Fe 2O 3 particle, the nano-sized Fe 2O 3 particle may increase microvascular permeability and cell lysis in lung epitheliums and disturb blood coagulation parameters significantly.

Inhalation Toxicity and Lung Toxicokinetics of C60 Fullerene Nanoparticles and Microparticles

While several recent reports have described the toxicity of water-soluble C60 fullerene nanoparticles, none have reported the toxicity resulting from the inhalation exposures to C60 fullerene nanoparticles or microparticles. To address this knowledge gap, we exposed male rats to C60 fullerene nanoparticles (2.22 mg/m3, 55 nm diameter) and microparticles (2.35 mg/m3, 0.93 microm diameter) for 3 h a day, for 10 consecutive days using a nose-only exposure system. Nanoparticles were created utilizing an aerosol vaporization and condensation process. Nanoparticles and microparticles were subjected to high-pressure liquid chromatography (HPLC), XRD, and scanning laser Raman spectroscopy, which cumulatively indicated no chemical modification of the C60 fullerenes occurred during the aerosol generation. At necropsy, no gross or microscopic lesions were observed in either group of C60 fullerene exposures rats. Hematology and serum chemistry results found statistically significant differences, although small in magnitude, in both exposure groups. Comparisons of bronchoalveolar (BAL) lavage fluid parameters identified a significant increase in protein concentration in rats exposed to C60 fullerene nanoparticles. BAL fluid macrophages from both exposure groups contained brown pigments, consistent with C60 fullerenes. C60 lung particle burdens were greater in nanoparticle-exposed rats than in microparticle-exposed rats. The calculated lung deposition rate and deposition fraction were 41 and 50% greater, respectively, in C60 fullerene nanoparticle-exposed group than the C60 fullerene microparticle-exposed group. Lung half-lives for C60 fullerene nanoparticles and microparticles were 26 and 29 days, respectively. In summary, this first in vivo assessment of the toxicity resulting from inhalation exposures to C60 fullerene nanoparticles and microparticles found minimal changes in the toxicological endpoints examined. Additional toxicological assessments involving longer duration inhalation exposures are needed to develop a better and more conclusive understanding of the potential toxicity of inhaled C60 fullerenes whether in nanoparticle or microparticle form.

Radiographic readings for asbestosis: Misuse of science—validation of the ILO classification

Radiographic readings for pneumoconiosis (both asbestosis and silicosis), even those using the International Labour Office (ILO) Classification, have received widespread negative coverage in the media and strong judicial rebuke. The medical literature over the past 90 years was reviewed for the relationships between radiographic severity (standardized as the ILO profusion score) and indices of exposure to silica or asbestos, tissue burden of silica particles or asbestos fibers, histologic fibrosis, various measurements of pulmonary function and mortality. Evidence from many different disciplines has demonstrated that the ILO profusion score correlates with occupational exposure, dust burden in the lung, histologic fibrosis and, more recently, with physiologic impairment and mortality. The ILO Classification has therefore been validated as a scientific tool. Its fraudulent misuse by "hired-gun" physicians, attorneys and elements of the compensation system to falsify claims of asbestosis and/or silicosis (often in the same claimant) must be condemned.

Indoor and outdoor submicrometer particles: Exposure and epidemiologic relevance (“the 3 indoor Ls”)

Airborne particles represent a very important pollutant with respect to healthy housing conditions. The snag is that in lack of indoor data epidemiological studies focusing on submicron and ultrafine (<100 nm in diameter) particles are usually forced to use outdoor particle concentrations only. On the other hand it is known that people spend most of their time indoors. The aim of this paper is therefore to give a short comprehensive overview of the indoor/outdoor problem with regard to submicron and ultrafine particles, investigating how indoor particle size distributions correlate with outdoor concentrations in the absence of significant indoor sources. In the absence of a major indoor source, total indoor particle number concentrations were always lower than outdoor concentrations. The highest ratios between indoor and outdoor concentrations tend to correlate with lower rather than higher total outdoor particle number concentrations. Concentration ratios depend on particle size. Time lags of the correlation coefficients between the concentrations of indoor and outdoor particles of different diameters have been determined to assess the time the particles need to enter the indoor site through closed modern-type windows. Typical lag times of 0.5-3 h between somewhat smaller indoor particles and somewhat larger outdoor particles have been observed. To assess the resulting particle burden for humans, a suitably weighted average emphasizing indoor aerosol particles must be used. To classify the health effects of particles of different diameters, different decreases of particle number concentrations depending on the particle sizes must be taken into account if indoor concentrations cannot be measured and outdoor concentrations are used in place of indoor measurements. In urban areas, ultrafine particles originate primarily from rapidly increasing traffic, which is the dominating source at many urban sites. The influence of traffic on outdoor and indoor concentrations is therefore of special interest.

Tracking Regional Anthropogenic Air Pollution: A Case Study in Israel

Typical mid-winter anthropogenic air pollution episodes are caused when pollutants are trapped in the lower atmospheric boundary layer due to the generation of surface inversion favored by synoptic conditions. We analyzed the optical properties of atmospheric aerosol particles obtained during one such episode using a sun/sky radiometer at two measurement sites: one located in the densely populated and industrialized central part of Israel, and the other in a reference site, about 150 km away. Aerosol optical thickness and volume size distributions showed an increased burden of fine aerosol particles in the central part of Israel. In order to verify the local origin and anthropogenic nature of the effect, the analysis was accompanied by examinations of the synoptic conditions, air mass backward trajectories, and conventional in situ air pollution measurements made by a ground-based sampling station. This case study shows the ability of optical measurements to track urban and industrial atmospheric air pollution expressed by high concentration of fine aerosol particles. In addition, it emphasizes the role of local Israeli air pollution sources and may explain the difference in the properties of long-term aerosol optical observations between the two sites. The advantages of the optical method presented are speed (almost instantaneous), automated measurement, and sensitivity to aerosol particle concentration as well as aerosol size fraction. The drawback is that the optical measurements discussed deal only with aerosol particles and cannot distinguish between different types of pollutant gases.

Corrosion of Modular Titanium Alloy Stems in Cementless Hip Replacement

Abstract Severe, localized corrosion of titanium-alloy femoral stems has been reported for specific designs of hip prostheses intended for fixation using acrylic cement. The purpose of the present study was to examine the possibility that corrosion might also occur when titanium-alloy stems are inserted without cement, but the body of the stem is modular in design. Fourteen (7 primary and 7 revision) cementless, modular-body, titanium-6% aluminum-4% vanadium alloy femoral stems of similar design were removed at revision surgery after 2 to 108 months in situ. The reason for removal was unexplained pain (4), femoral or acetabular loosening (4), infection (3), recurrent dislocation (2), or component malposition (1). The devices and, in selected cases, tissue from the joint psuedocapsule were studied with the use of light and scanning electron microscopy. Fretting corrosion products were characterized using energy dispersive x-ray analysis, selected area diffraction, and micro-Raman spectroscopy. Damage at the modular body connections was absent in 3 stems, mild in 6, moderate in 4, and severe in 1. The surface damage was characterized predominately by fretting scars and by pitting and etching. Thick deposits of mixed titanium oxides were found adherent to the stem at the sites of corrosion and as 0.01 to 200 micrometer particles within histiocytes and multinucleated giant cells in the joint pseudocapsule. Fretting corrosion at the modular-body junctions of titanium-alloy femoral stems can generate solid degradation products, adding to the particulate burden of the periprosthetic tissues and potentially accelerating bearing-surface wear by a third-body mechanism. Both of these features can potentiate the development and progression of osteolysis. In addition, fretting corrosion can increase the potential for structural failure of the device. These findings stress the importance of the design of modular junctions to minimize corrosion and the generation of corrosion products.

Morphometric Analysis of Particulate Debris Extracted by Four Different Embolic Protection Devices from Coronary Arteries, Aortocoronary Saphenous Vein Conduits, and Carotid Arteries

Different embolic protection devices have been introduced for endovascular interventions: filters or balloon occlusion and aspiration systems. Despite widening use in a variety of vascular beds and clinical syndromes, little is known about the particulate burden liberated from different vascular beds and caught by different protection devices. We performed histologic and morphometric analyses of particulate debris captured during stenting of degenerated saphenous vein bypass grafts and native coronary arteries during acute myocardial infarction or during elective intervention and carotid arteries to assess the relative performance of different protection devices. We analyzed 232 interventions (90 saphenous vein bypass grafts, 77 native coronary arteries, and 65 carotid arteries) with 4 different devices (65 FilterWires, 99 Interceptors, 41 GuardWires, and 27 Proxis catheters) using the RapidVue particle analyzer. No difference in embolic volume retrieved was demonstrated between devices in saphenous vein bypass grafts and carotid interventions. A smaller volume of particulate debris was retrieved by the GuardWire compared with the FilterWire and the Proxis catheter in native coronary artery interventions. The Interceptor and the GuardWire captured more smaller particles than did the FilterWire or Proxis catheter. During saphenous vein bypass graft or carotid intervention, different embolic protection strategies were performed similarly. In native coronary artery stenting, however, proximal embolic protection retrieved larger amounts of debris than did distal filters or occlusion devices. These data may allow greater tailoring of embolic protection device development and application in specific anatomic locales.

Abrasive Blasting Agents: Designing Studies to Evaluate Relative Risk

Workers exposed to respirable crystalline silica used in abrasive blasting are at increased risk of developing a debilitating and often fatal fibrotic lung disease called silicosis. The National Institute for Occupational Safety and Health (NIOSH) recommends that silica sand be prohibited as abrasive blasting material and that less hazardous materials be used in blasting operations. However, data are needed on the relative risks associated with exposure to abrasive blasting materials other than silica. NIOSH has completed acute studies in rats (Hubbs et al., 2001; Porter et al., 2002). To provide dose-response data applicable to making recommendation for occupational exposure limits, NIOSH has collaborated with the National Toxicology Program (NTP) to design longer term studies with silica substitutes. For risk assessment purposes, selected doses will include concentrations that are relevant to human exposures. Rat lung burdens achieved should be comparable to those estimated in humans with working lifetime exposures, even if this results in “overloading” doses in rats. To quantify both dose and response, retained particle burdens in the lungs and lung-associated lymph nodes will be measured, as well as biochemical and pathological indices of pulmonary response. This design will facilitate assessment of the pulmonary fibrogenic potential of inhaled abrasive blasting agents at occupationally relevant concentrations.

Titanium Dioxide: Inhalation Toxicology and Epidemiology

Titanium dioxide (TiO(2)) is manufactured worldwide in large quantities for use in a wide range of applications and is normally considered to be toxicologically inert. Findings of tumours in the lungs of rats exposed chronically to high concentrations of TiO(2), but not in similarly exposed mice or hamsters, suggest that the tumorigenic response may be a rat-specific phenomenon but nonetheless raises concerns for potential human health effects. With the limited toxicological understanding of species differences in response to inhaled TiO(2) and a similarly limited amount of epidemiological information with respect to TiO(2) exposure in the workplace, a consortium of TiO(2) manufacturers in Europe (under the European Chemistry Industry Council; CEFIC) and in North America (under the American Chemistry Council; ACC) initiated a programme of research to investigate inter-species differences as a result of exposure to TiO(2) and to conduct detailed epidemiological surveys of the major manufacturing sites. The toxicology studies exposed rats, mice and hamsters to pigment-grade TiO(2) (PG-TiO(2), 0, 10, 50 and 250 mg m(-3)) or ultrafine TiO(2) (UF-TiO(2), 0, 0.5, 2 and 10 mg m(-3)) for 90 days and the lung burdens and tissue responses were evaluated at the end of the exposure period and for up to 1 year after exposure. Results demonstrated clear species differences. Rats and mice had similar lung burdens and clearance rates while hamsters showed high clearance rates. At high lung particle burdens, rats showed a marked progression of histopathological lesions throughout the post-exposure period while mice and hamsters showed minimal initial lesions with recovery apparent during the post-exposure period. Lung neutrophil responses, a sensitive marker of inflammatory changes, reflected the development or recovery of the histopathological lesions. The use of surface area rather than gravimetric lung burden provided closer correlates of the burden to the biological effect across both TiO(2) types. The epidemiological investigations evaluated the mortality statistics at 11 European and 4 US TiO(2) manufacturing plants. They concluded that there was no suggestion of any carcinogenic effect associated with workplace exposure to TiO(2).

Organic Aerosol Growth Mechanisms and Their Climate-Forcing Implications

Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.8 watt per square meter cooling and +0.3 watt per square meter warming.

Accumulation in liver and spleen of metal particles generated at nonbearing surfaces in hip arthroplasty

Systemic migration of metal particles generated at nonbearing surfaces rather than the intended primary bearing was studied in postmortem specimens from 30 patients with total hip arthroplasty. Using light and electron microscopy with x-ray microanalysis, submicrometer metal particles were identified within macrophages in the liver and/or the spleen in 11 of 15 patients with a revised arthroplasty and in 2 of 15 patients with primary hip arthroplasty. The macrophages formed focal aggregates in the organs without apparent toxicity. Fretting at ancillary fixation devices, loose components, and modular connections can generate a substantial volume of debris. These particles are in addition to those generated at the bearing surfaces, further increasing both the local and systemic particulate burdens. While all components can be associated with the distant spread of particles and metal ions, it is the environment of revision arthroplasty that provides the greatest potential for the generation and systemic dissemination of wear debris. The long-term effects of accumulated wear particles in the liver and spleen are unknown.

Spatial and temporal variability of high resolution reduced nitrogen concentrations in the Fraser Valley

We present high resolution measurements of ammonia (NH3) and particle-ammonium (NH4+) collected during the Pacific 2001 experiment at an urban, sub-urban and high elevation site. These data are used to conduct a detailed instrument inter-comparison and to characterize the sites. The data are interpreted with respect to; the degree to which the sites are representative, the degree of sensitivity to inorganic particle burdens to NH3 availability and controls on reduced nitrogen (NHx) variability and partitioning. Ammonia measurements from wet effluent diffusion denuders (WEDD), annular diffusion denuders and a tunable diode laser spectrometer generally lie within a factor of 1.5 across a range of observed concentrations of 0–0.25 μmol m−3, although individual observations differed by more than a factor of two. The high resolution (2 min average) data from the WEDD systems are used to calculate a coefficient of variability which is used to assess the degree to which the measurement sites are spatially representative. The results indicate the sub-urban site is the most spatially representative. Ammonia concentrations at this site exhibit variability on time scales of less than 4 h that is comparable to that of ozone. Data collected in the urban setting indicate persistent measurable NH3 concentrations and that NH4+ dominates NHx. Conversely, the high elevation site shows a much greater degree of variability due in part to the influence of meteorological coupling and decoupling from the underlying valley, domination of NHx by NH3 and a stronger coupling of NH3 and NH4+.

Organic composition of aerosol particulate matter during a haze episode in Kuala Lumpur, Malaysia

The solvent-extractable compounds of urban airborne particulate matter were analyzed to determine the distributions of homologous and biomarker tracers. Samples were collected by high-volume air filtration during the haze episode of 1997 around the University of Malaya campus near Petaling Jaya, a suburb of Kuala Lumpur, Malaysia. These results show that the samples contain n-alkanes, n-alkan-2-ones, n-alkanols, methyl n-alkanoates, n-alkyl nitriles, n-alkanals, n-alkanoic acids, levoglucosan, PAHs, and UCM as the dominant components, with minor amounts of terpenoids, glyceryl esters and sterols, all derived from natural biogenic sources (vascular plant wax), from burning of biomass, and from anthropogenic utilization of fossil fuel products (lubricating oil, vehicle emissions, etc.). Some compositional differences are observed in the samples and greater atmospheric concentrations were found for almost all organic components in the samples collected near a roadway. The results interpreted in terms of major sources are due to local build-up of organic contaminants from vehicular emissions, smoke from biomass burning, and natural background as a result of the atmospheric stability during the haze episodes. The organic components transported in from areas outside the region, assuming all smoke components are external to the city, amount to about 30% of the total organic particle burden.

Comparison of predicted and experimental erosion estimates in slurry ducts

Computational models for the impact velocity and impact angle in a bend have been successfully applied to the flow field and validated by electrical resistance tomography (ERT) to confirm the position of particle burdens. Particle impact parameters from this work have been used as inputs to erosion models to predict wall wastage rates in a R c/ D=1.2 bend and a upstream straight pipe section. The location of damage and the levels of wall wastage agree well with those obtained from erosion trials conducted on a full scale loop rig with AISI 304 stainless steel pipework. Well-distributed but asymmetric particulate flows of sand in water have been studied at average flow velocities of 3 m s −1. Predicted erosion damage levels and locations are compared to non-destructive ultrasonic and gravimetric measurements as well as wall thickness measurements made with a micrometer after cutting the pipe and bends sections.

Pulmonary Responses of Mice, Rats, and Hamsters to Subchronic Inhalation of Ultrafine Titanium Dioxide Particles

A multispecies, subchronic, inhalation study comparing pulmonary responses to ultrafine titanium dioxide (uf-TiO(2)) was performed. Female rats, mice, and hamsters were exposed to aerosol concentrations of 0.5, 2.0, or 10 mg/m(3) uf-TiO(2) particles for 6 h/day, 5 days/week, for 13 weeks. Following the exposure period, animals were held for recovery periods of 4, 13, 26, or 52 weeks (49 weeks for the uf-TiO(2)-exposed hamsters) and, at each time point, uf-TiO(2) burdens in the lung and lymph nodes and selected lung responses were examined. The responses studied were chosen to assess a variety of pulmonary parameters, including inflammation, cytotoxicity, lung cell proliferation, and histopathological alterations. Retained lung burdens increased in a dose-dependent manner in all three species and were at a maximum at the end of exposures. Mice and rats had similar retained lung burdens at the end of the exposures when expressed as mg uf-TiO(2)/mg dry lung, whereas hamsters had retained lung burdens that were significantly lower. Lung burdens in all three species decreased with time after exposure, and, at the end of the recovery period, the percentage of the lung particle burden remaining in the 10 mg/m(3) group was 57, 45, and 3% for rat, mouse, and hamster, respectively. The retardation of particle clearance from the lungs in mice and rats of the 10 mg/m(3) group indicated that pulmonary particle overload had been achieved in these animals. Pulmonary inflammation in rats and mice exposed to 10 mg/m(3) was evidenced by increased numbers of macrophages and neutrophils and increased concentrations of soluble markers in bronchoalveolar lavage fluid (BALF). The initial neutrophil response in rats was greater than in mice, whereas the relative increase of macrophages was less than in mice. The neutrophilic response of rats, but not mice, declined in a time-dependent manner correlating with declining lung burdens; however, the fraction of recovered neutrophils at 52 weeks postexposure was equivalent in the two species. Consistent increases in soluble indicators of toxicity in the BALF (LDH and protein) occurred principally in rats and mice exposed to 10 mg/m(3) and diminished with time postexposure. There were no significant changes in cellular response or with markers indicating toxicity in hamsters, reflecting the capacity of these animals to rapidly clear particles from the lung. Progressive epithelial and fibroproliferative changes were observed in rats of the 10 mg/m(3) group. These lesions consisted of foci of alveolar epithelial proliferation of metaplastic epithelial cells (so-called alveolar bronchiolization) circumscribing aggregated foci of heavily particle-laden macrophages. The observed epithelial proliferative changes were also manifested in rats as an increase in alveolar epithelial cell labeling in cell proliferation studies. Associated with these foci of epithelial proliferation were interstitial particle accumulation and alveolar septal fibrosis. These lesions became more pronounced with increasing time postexposure. Epithelial, metaplastic, and fibroproliferative changes were not noted in either mice or hamsters. In summary, there were significant species differences in the pulmonary responses to inhaled uf-TiO(2) particles. Under conditions where the lung uf-TiO(2) burdens were equivalent, rats developed a more severe inflammatory response than mice and, subsequently, developed progressive epithelial and fibroproliferative changes. Clearance of particles from the lung was markedly impaired in mice and rats exposed to 10 mg/m(3) uf-TiO(2), whereas clearance in hamsters did not appear to be affected at any of the administered doses. These data are consistent with the results of a companion study using inhaled pigmentary (fine mode) TiO(2) (Bermudez et al., 2002) and demonstrate that the pulmonary responses of rats exposed to ultrafine particulate concentrations likely to induce pulmonary overload are different from similarly exposed mice and hamsters. These differences can be explained both by pulmonary respy response and by particle dosimetry differences among these rodent species.

Simulating the Formation of Secondary Organic Aerosol from the Photooxidation of Toluene

Environmental Context. Atmospheric particulate material can affect climate by absorbing and scattering solar radiation and by altering the properties of clouds. They are also implicated as a health risk. Secondary organic aerosol (SOA) material makes an important contribution to this particulate burden. SOA material results from the transfer of gas-phase species into a particle state after the formation of products from the reaction of atmospheric volatile organic compounds (VOCs) with oxygen. SOA from the oxidation of aromatic hydrocarbons, such as toluene, a gasoline fuel component, is important in the polluted urban environment and yet formation mechanisms are not well understood. Abstract. The formation and composition of secondary organic aerosol (SOA) from the gas-phase photooxidation of toluene has been simulated using the Master Chemical Mechanism version 3.1 (MCM v3.1) coupled to a representation of the transfer of organic material from the gas phase to a particle phase. The mechanism was tested against data from a series of toluene photooxidation experiments performed at the European Photoreactor (EUPHORE) outdoor smog chamber in Valencia, Spain. Simulated aerosol mass concentrations compared reasonably well with the measured SOA data after absorptive partitioning coefficients were increased by a factor of between 20 and 80, although the simulated onset of SOA growth was delayed with respect to the experiments. A simplified representation of peroxyhemiacetal adduct formation, from the reaction of organic hydroperoxides with aldehydes in the condensed organic phase, was included in the mechanism and this reduced the required scaling of partitioning coefficients and reduced the time-lag in simulated SOA growth. These observations, and the dependence of SOA formation efficiency upon the initial NO concentration, strongly imply the significant occurrence of association reactions in the condensed organic phase and the important role of organic hydroperoxides in SOA formation. Aerosol data from photooxidation experiments of intermediate degradation products (butenedial, 4-oxo-pentenal, and ortho-cresol) were also simulated using the developed mechanism.

Visualization of Asymmetric Solids Distribution in Horizontal Swirling Flows Using Electrical Resistance Tomography

Efficient slurry transportation is vital to many industries. It has been proposed that helically formed pipes, which can be used to keep particulate solids in suspension, should be applied to enhance the distribution of solids in piped slurries. The use of a new in-situ measurement method based on electrical impedance tomography is proposed to assist in understanding the effect of particle suspension and as well as the effect on the wear of pipes by solid particle impingement due to the application of such a swirl-inducing pipe. In the absence of accurate predictive models for such complex flows, it is demonstrated that this method enables direct visualization of the solids concentration profiles in the pipes. Through the application of an advanced impedance image reconstruction algorithm and other analysis software, the asymmetric solids concentration distribution in horizontal swirling flows can be quantified. Particle concentration regimes are reported as a function of the water axial flow velocity and the downstream distance from the swirl-inducing pipe section. The nature of the solids distribution at a typical cross-section is reproducible and takes the form of a crescent region of a higher solids concentration, re-orientated in the direction of swirl by approximately π/2 from the normal settling position. Low concentration areas in a crescent shape appear on the opposite semi-circumference to the particle burden. These appear to develop into a ring structure as the water flow increases to a high axial velocity. At a high flow velocity, the mode of particle dispersion along the length of the pipeline appears to take the form of a group of ellipses. Larger ellipses were observed near the swirl-inducing pipe.