Coal fly ash- and copper smelter dust-induced modulation of ex vivo production of tumor necrosis factor-alpha by murine macrophages: effects of metals and overload

An evaluation of the toxicological aspects and potential doses from the inhalation of coal combustion products

This paper reviews toxicological literature pertaining to coal combustion products (CCPs) inhalation and presents case studies on the inhalation of CCPs from the Kingston Fossil Plant area and from the Colbert Fossil Plant CCP landfill site. While most research regarding coal plant emissions focuses on fly ash, this article takes a holistic approach to examining not only emitted particulate matter such as fly ash, but also the theoretical calculated doses of landfilled CCPs. Furthermore, these doses are compared to in vitro and in vivo studies in order to highlight differences between laboratory-based studies and to emphasize the difficulty in extrapolating effects from inhalation exposures. In both case studies, fugitive emissions from the Kingston ash spill or the Colbert CCP-handling operations did not exceed any national ambient air quality standards or reference concentrations for individual components. Adverse effects such as mild pulmonary inflammation noted in the reviewed literature were in response to doses much higher than would be likely to occur in humans exposed to landfilled CCPs. We conclude that the doses for fugitive emissions calculated herein do not appear to be high enough to elicit a measurable adverse response in humans.

Understanding the chemical properties of macerals and minerals in coal and its potential application for occupational lung disease prevention

Recent increases in oil price further strengthen the argument that coal and coal products will play an increasingly important role in fulfilling the energy needs of our society. Coal is an aggregate of heterogeneous substances composed of organic (macerals) and inorganic (minerals) materials. The objective of this review was to assess whether some chemical parameters in coal play a role in producing environmental health problems. Basic properties of coal--such as chemical forms of the organic materials, structure, compositions of minerals--vary from one coal mine region to another as well as from coals of different ranks. Most importantly, changes in chemical properties of coals due to exposure to air and humidity after mining--a dynamic process--significantly affect toxicity attributed to coal and environmental fate. Although coal is an extremely complex and heterogeneous material, the fundamental properties of coal responsible for environmental and adverse health problems are probably related to the same inducing components of coal. For instance, oxidation of pyrite (FeS2) in the coal forms iron sulfate and sulfuric acid, which produces occupational lung diseases (e.g., pneumoconiosis) and other environmental problems (e.g., acid mine drainage and acid rain). Calcite (CaCO3) contained in certain coals alters the end products of pyrite oxidation, which may make these coals less toxic to human inhalation and less hazardous to environmental pollution. Finally, knowledge gained on understanding of the chemical properties of coals is illustrated to apply for prediction of toxicity due to coal possibly before large-scale mining and prevention of occupational lung disease during mining.

Airborne crystalline silica concentrations at coal-fired power plants associated with coal fly ash

This study presents measurements of airborne concentrations of respirable crystalline silica in the breathing zone of workers who were anticipated to encounter coal fly ash. Six plants were studied; two were fired with lignite coal, and the remaining four plants used bituminous and subbituminous coals. A total of 108 personal breathing zone respirable dust air samples were collected. Bulk samples were also collected from each plant site and subjected to crystalline silica analysis. Airborne dust particle size analysis was measured where fly ash was routinely encountered. The results from bituminous and subbituminous fired plants revealed that the highest airborne fly ash concentrations are encountered during maintenance activities: 0.008 mg/m3 to 96 mg/m3 (mean of 1.8 mg/m3). This group exceeded the threshold limit values (TLV) in 60% of the air samples. During normal production activities, airborne concentrations of crystalline silica ranged from nondetectable to 0.18 mg/m3 (mean value of 0.048 mg/m3). Air samples collected during these activities exceeded the current and proposed TLVs in approximately 54% and 65% of samples, respectively. Limited amounts of crystalline silica were detected in samples collected from lignite-fired plants, and approximately 20% of these air samples exceeded the current TLV. Particle size analysis in areas where breathing zone air samples were collected revealed mass median diameters typically between 3 microm and 8 microm. Bulk and air samples were analyzed for all of the common crystalline silica polymorphs, and only alpha quartz was detected. As compared with air samples, bulk samples from the same work areas consistently yielded lower relative amounts of quartz. Controls to limit coal fly ash exposures are indicated during some normal plant operations and during episodes of short term, but high concentrations of dust that may be encountered during maintenance activities, especially in areas where ash accumulations are present.

Arsenic and cigarette smoke synergistically increase DNA oxidation in the lung

Epidemiological evidence has indicated that arsenic and cigarette smoking exposure act synergistically to increase the incidence of lung cancer. Since oxidative damage of DNA has been linked to cancer, our hypothesis is that aerosolized arsenic and cigarette smoke work synergistically to increase oxidative stress and increase DNA oxidation in the lung. To test this hypothesis male Syrian golden hamsters were exposed to room air (control), aerosolized arsenic compounds (3.2 mg/m3 for 30 minutes), cigarette smoke (5 mg/m3 for 30 minutes), or both smoke and arsenic. Exposures were for 5 days/week for 5 or 28-days. Animals were sacrificed one day after the last exposure. In the 28-day group, glutathione levels and DNA oxidation (8-oxo-2'-deoxyguanosine (8-oxo-dG)) were determined. Our results show that in the 28-day arsenic/smoke group there was a significant decrease in both the reduced and total glutathione levels compared with arsenic or smoke alone. This correlated with a 5-fold increase in DNA oxidation as shown by HPLC. Immunohistochemical localization of 8-oxo-dG showed increase staining in nuclei of airway epithelium and subadjacent interstitial cells. These results show that dual exposure of arsenic and cigarette smoke at environmentally relevant levels can act synergistically to cause DNA damage.

Winter urban air particles from Rome (Italy): effects on the monocytic-macrophagic RAW 264.7 cell line

Epidemiological data show an association between exposure to elevated levels of particulate matter (PM), in particular the fine fraction (<2.5 microm in diameter), and an increase in cardiovascular mortality and respiratory symptoms. The aim of this study was to compare the in vitro toxicity of coarse and fine particulate matter collected with a cascade impactor during winter in an urban area of Rome in relation to their physicochemical characterization (size distribution and chemical composition) as assessed by analytical electron microscopy (SEM/EDX). The X-ray microanalysis data of single particles of coarse and fine matter were analyzed by hierarchical cluster analysis to determine the principal component of the two granulometric fractions. The main chemical difference between the two fractions was the greater abundance of carbonaceous particles in the fine fraction. We compared the ability of coarse and fine fractions, carbon black (CB), and residual oil fly ash (ROFA) to induce arachidonic acid release and tumor necrosis factor-alpha (TNF-alpha) production in the monocytic-macrophagic RAW 264.7 cell line at concentrations of 30 and 120 microg/mL. Our results showed that CB and ROFA were consistently less effective than both fractions of urban particles at inducing an inflammatory reaction in RAW 264.7 cells. Both PM fractions dose-dependently increased TNF-alpha production in RAW 264.7 cells after 5 and 24h of incubation, and only the TNF-alpha production induced by coarse particles at 30 microg/mL decreased significantly (P<0.01) after 24h of treatment. In our in vitro model the winter fine fraction was more reactive than the winter coarse fraction, in contrast to a previously examined summer sample. In the summer sample, coarse particles produced higher levels of inflammatory mediators than fine particles and the CB was consistently less effective than the urban particles. The different behaviors between summer and winter urban fractions may be due to their different physicochemical characteristics; in fact, the comparison of the two samples' characterization by SEM/EDX and X-ray photoelectron spectroscopy (XPS) analysis showed that in winter the carbonaceous particles are more abundant than in summer and that winter particles carry a greater quantity of organic compounds. We suggest that the higher concentration of organic compounds on fine carbonaceous particles may partially explain the higher activation of RAW 264.7 cells by fine particles.

Adjuvant activity of various diesel exhaust and ambient particles in two allergic models

In the framework of an EU study entitled "Respiratory Allergy and Inflammation Due to Ambient Particles" (RAIAP), various collected particulate matter samples were to be tested for their adjuvant potency in two animal models of allergy. A pollen allergy model in the Brown Norway (BN) rat and an ovalbumin model in the BALB/c mouse were used in this study to compare the discriminatory value of these two models and to evaluate them for later studies of collected RAIAP-samples. Two different sources of diesel exhaust particles (DEP I and DEP II ), a residual oil fly ash source (ROFA), and two sources of ambient particles (Ottawa dust, EHC-93, and road tunnel dust, RTD) were tested. Rats were sensitized intratracheally with Timothy grass pollen (Phleum pratense, 200 microl, 10 mg/ml) on d 0, challenged on d 21, and examined on d 25. Mice were sensitized intranasally at d 0 and 14, challenged intranasally at d 35, 38, and 41 (50 microl, 0.4 mg ovalbumin/ml), and examined at d 42. Particulate matter (PM) was administered either during the sensitization phase only or during the sensitization and challenge phases (for mice only) or during the challenge phase only. In the pollen model, only DEP I, but not DEP II, ROFA, EHC-93, and RTD, stimulated the immunoglobulin (Ig) E and IgG1 response in serum to pollen allergens. In addition to this adjuvant effect noted, no other biomarkers in lung or bronchoalveolar lavage (BAL) revealed adjuvant activity in the pollen model. In the BAL of BN rats exposed to a combination of pollen and PM, the percentages of eosinophilic granulocytes were decreased compared to the BAL of BN rats immunized with pollen only. In the ovalbumin model, the IgE levels in serum were increased in mice after coexposure to ovalbumin and PM (including DEPI, DEPII, ROFA, EHC-93, and RTD) in the sensitization phase but not after coexposure during the challenge phase only. The inflammatory response was greater in the lung, predominantly the influx of eosinophilic granulocytes, as was observed by both histopathological examination and BAL analysis. In addition, BAL levels of inflammatory interleukin (IL)-4 were increased. Based on the IgE antibody response to ovalbumin, the ovalbumin model ranked the adjuvant capacity of the particles in the following order: RTD > ROFA > EHC-93 > DEPI > DEPII. In conclusion, the ovalbumin model is a sensitive system to detect adjuvant activity of airborne particles, whereas the pollen-induced allergy model in rat was less sensitive.

Oxidative stress and NFkappaB activation in the lungs of rats: a synergistic interaction between soot and iron particles

Particulate matter (PM) has been associated with a variety of adverse health effects primarily involving the cardiopulmonary system. However, the precise biological mechanisms to explain how exposure to PM exacerbates or directly causes adverse effects are unknown. Particles of varying composition may play a critical role in these effects. To study such a phenomenon, a simple, laminar diffusion flame was used to generate aerosols of soot and iron particles in the ultrafine size range. Exposures of healthy adult rats were for 6 h/day for 3 days. Conditions used included exposure to soot only, iron only, or a combination of soot and iron. We found animals exposed to soot particles at 250 microg/m3 had no adverse respiratory effects. Exposure to iron alone at a concentration of 57 microg/m3 also had no respiratory effects. However, the addition of 45 microg/m3 of iron to soot with a combined total mass concentration of 250 microg/m3 demonstrated significant pulmonary ferritin induction, oxidative stress, elevation of IL-1beta, and cytochrome P450s, as well as activation of NFkappaB. These findings suggest that a synergistic interaction between soot and iron particles account for biological responses not found with exposure to iron alone or to soot alone.

Metals mimic airway epithelial injury induced by in vitro exposure to Utah Valley ambient particulate matter extracts

Epidemiologic studies have shown positive associations between changes in ambient particulate matter (PM) levels in Utah Valley during 1986-1988, and the respiratory health of the local population. Ambient PM reductions coincided with closure of an open-hearth steel mill, the major industrial source of particulate emissions in the valley. In this report, water extracts of PM filters from steel mill operational (UE-86, UE-88) and closure (UE-87) periods were analyzed for their elemental composition. Their relative toxicity was determined by exposing primary rodent airway epithelial cultures to equal masses of extracted material. To elucidate extract subcomponents mediating the effects observed, cells were also exposed to surrogate metal mixtures. Potential interactions between the two predominant metals in the UE-86/88 samples, zinc (Zn) and copper (Cu), were further investigated. Data indicated that, relative to the UE-87 (plant closed) sample, UE-86/88 samples contained more sulfate, calcium, potassium,magnesium and, although present in much lower amounts, a variety of metals including Zn,Cu, iron, lead, strontium, nickel, manganese, and vanadium (V). Cell exposure to UE-86 and UE-88, but not UE-87, resulted in time- and concentration-dependent epithelial injury based on biochemical and light/electron microscopic changes. Cell injury induced by metal mixtures containing equivalent amounts of Zn + Cu + V was commensurate with that induced by the corresponding extract, although divergent antioxidant responses were observed. Exposure to Zn + Cu resulted in significantly greater epithelial toxicity and stress (c-Jun N-terminal protein kinase activation) responses than did exposure to Zn or Cu individually. The parallel epithelial injury induced by the extracts and their surrogate Zn + Cu + V mixtures suggests that these metals are mediating the acute airway epithelial effects observed; however, metal interactions appear to play a critical role in the overall cellular effects induced by the PM-derived extracts. These experimental findings are in good accord with epidemiologic reports of adverse airway and respiratory health health effects in Utah Valley residents.

Inhalation health effects of fine particles from the co-combustion of coal and refuse derived fuel

This paper is concerned with health effects from the inhalation of particulate matter (PM) emitted from the combustion of coal, and from the co-combustion of refuse derived fuel (RDF) and pulverized coal mixtures, under both normal and low NO(x) conditions. Specific issues focus on whether the addition of RDF to coal has an effect on PM toxicity, and whether the application of staged combustion (for low NO(x)) may also be a factor in this regard. Ash particles were sampled and collected from a pilot scale combustion unit and then re-suspended and diluted to concentrations of approximately 1000 microg/m(3). These particles were inhaled by mice, which were held in a nose-only exposure configuration. Exposure tests were for 1 h per day, and involved three sets (eight mice per set) of mice. These three sets were exposed over 8, 16, and 24 consecutive days, respectively. Pathological lung damage was measured in terms of increases in lung permeability. Results show that the re-suspended coal/RDF ash appeared to cause very different effects on lung permeability than did coal ash alone. In addition, it was also shown that a "snapshot" of lung properties after a fixed number of daily 1-h exposures, can be misleading, since apparent repair mechanisms cause lung properties to change over a period of time. For the coal/RDF, the greatest lung damage (in terms of lung permeability increase) occurred at the short exposure period of 8 days, and thereafter appeared to be gradually repaired. Ash from staged (low NO(x)) combustion of coal/RDF appeared to cause greater lung injury than that from unstaged (high NO(x)) coal/RDF combustion, although the temporal behavior and (apparent) repair processes in each case were similar. In contrast to this, coal ash alone showed a slight decrease of lung permeability after 1 and 3 days, and this disappeared after 12 days. These observations are interpreted in the light of mechanisms proposed in the literature. The results all suggest that the composition of particles actually inhaled is important in determining lung injury. Particle size segregated leachability measurements showed that water soluble sulfur, zinc, and vanadium, but not iron, were present in the coal/RDF ash particles, which caused lung permeabilities to increase. However, the differences in health effects between unstaged and staged coal/RDF combustion could not be attributed to variations in pH values of the leachate.

Airway hyperresponsiveness caused by aerosol exposure to residual oil fly ash leachate in mice

Particulate air pollution is associated with exacerbation of asthma and other respiratory disorders. This study sought to further characterize the pulmonary effects of residual oil fly ash (ROFA), an experimentally useful surrogate for combustion-derived particulates in ambient air. Mice were exposed to aerosols of the soluble leachate of residual oil fly ash (ROFA-s). Physiologic testing of airway function (non invasive plethysmography) showed increased Penh, an index of airway hyperresponsiveness (AHR), in a time- and dose-dependent manner after exposure to ROFA-s. BAL analysis showed a minor influx of neutrophils, which was maximal at 12 h after exposure and essentially resolved by the time point of maximal AHR (48 h after exposure). The AHR caused by ROFA-s was reproduced by a mixture of its major metal components (Ni, V, Zn, Co, Mn, Cu) but not by any individual metal alone. Systemic pretreatment of mice with the antioxidant dimethylthiourea abrogated ROFA-s-mediated AHR. Analysis of mice of varying ages showed that ROFA-s had no marked effect on airway responsiveness of 2-wk-old mice, in contrast to the AHR seen in 3- and 8-wk old mice. ROFA-s-mediated AHR was unchanged in neurokinin 1 receptor knockout mice and in mice treated with an neurokinin antagonist, arguing against a role for this mediator in ROFA-s-mediated effects. Data indicate that ROFA-s mediates AHR in mice through antioxidant-sensitive mechanisms that require multiple metal constituents. Maturational differences in susceptibility to ROFA-induced AHR may be useful for further studies of mechanisms of particle effects.

Contribution of endotoxin in macrophage cytokine response to ambient particles in vitro

Ambient particles may cause pulmonary inflammation with ensuing morbidity. Particle-induced production of proinflammatory cytokines in vitro has been used as an indicator of particle toxicity. To identify particle components that were related to particle toxicity, Andersen dichotomous impactors were used to collect ambient fine (PM(2.5)) and coarse (PM(2.5-10)) particles in central Taiwan with extraction in endotoxin-free water. Mouse monocyte-macrophage cell line RAW 264.7 cells were exposed to particle extracts at 40 micro g/ml for 16 h, and tumor necrosis factor-alpha (TNF-alpha) was measured in the medium by enzyme-linked immunosorbent assay (ELISA). Cell viabilities were all greater than 82%. Coarse particles stimulated higher TNF-alphaproduction than fine particles, and this was associated with greater particulate endotoxin content. Polymyxin B inhibited 42% of TNF-alpha production elicited by coarse particles and 32% of TNF-alpha production elicited by fine particles. In fine particles, TNF-alpha production was negatively correlated with Zn content, while no element in coarse particles correlated with TNF-alpha production. Results suggest that endotoxin and other components may be important factors for TNF-alpha production by macrophages in vitro.