Fate of inhaled fly ash in hamsters

To determine pulmonary deposition, translocation, and clearance of inhaled fly ash, hamsters received a single 95-min nose-only exposure to neutron-activated fly ash. Over a period of 99 days postexposure, the hamsters were sacrificed in groups of six animals. Lungs, liver, kidneys, decapitated and skinned carcass, pelt, head, gastrointestinal tract, urine, and feces were collected for analysis of the radionuclide tracers ⁴⁶Sc, ⁵⁹Fe, and ⁶⁰Co by γ-ray spectrometry. The fly ash burden estimates as determined by the radionuclides ⁴⁶Sc and ⁵⁹Fe are in good agreement for the majority of samples analyzed. Such close agreement indicates fly ash particulate levels in the lungs, carcass, head, pelt, GI tract, and feces rather than leached radionuclides. Relative to the ⁴⁶Sc and ⁵⁹Fe-based estimates, fly ash deposition estimates obtained with the isotope ⁶⁰Co were appreciably lower for the lungs and appreciably higher for one or more sacrifice times for carcass, liver, head, pelt, and urine samples. This indicates that ⁶⁰Co (and thus the element cobalt) selectively leached from fly ash deposited in the deep lung, translocated to other sites, and was excreted in the urine. An estimated average of 63 μg fly ash, or 2 to 3% of the inhaled fly ash, was initially retained in the respiratory tract. The estimated biological half-times of the fly ash were 2.6 and 34.5 days, probably for the airways and for the deep lung, respectively. After 99 days, the mean lung burden had decreased to about 10% of its initial value.     

Acute and subchronic inhalation exposures of hamsters to nickel-enriched fly ash.

One 6-hr inhalation exposure of hamsters to Ni-enriched fly ash (NEFA) aerosol (respirable aerosol concentration ～200 μg/liter) deposited about 80 μg in the deep lung, of which 75 μg was still present 30 days postexposure. The animals tolerated the exposure well during the 30-day postexposure observation period.Two-month exposures of hamsters to NEFA or fly ash (FA) aerosols (～185 μg/liter) resulted in a deep lung burden of about 5.7 mg, dark discoloration of lungs, heavily dustladen macrophages, and significantly higher lung weights than in controls, but only minimal inflammatory reaction and no deaths. There was no difference between NEFA and FA effects. The NEFA contained 9% Ni; FA contained 0.03% NI.The results of this study indicate low acute and subchronic toxicity and slow lung clearance of NEFA and FA.     

Effects of fly ash inhalation on murine immune function: Effects on systemic response

Mice were exposed to fly ash at levels ranging from 728–2221 μg/m³ respirable for varying periods of time, and several immunological parameters were measured. Little change was noted in splenic response to mitogens or cytolytic ability. Splenic lymphocytes from fly ash-exposed mice incorporated significantly more thymidine following subcutaneous sensitization with BCG, although no differences were noted in response of these lymphocytes to PPD. Fly ash exposure of greater than 1 week caused a suppression of antibody response to aerosols of Escherichia coli in the spleen, but not in the mediastinal lymph nodes. Following 3–4 weeks of fly ash exposure, no changes in splenic antibody responses were noted following intravenous injections of LPS or intratracheal injections of DNP-Ficoll. However, after 9 months exposure at higher concentrations of fly ash, splenic plaque-forming responses were significantly suppressed after both aerosol and intratracheal exposure to antigen.     

The utilization of the rabbit alveolar macrophage and Chinese hamster ovary cell for evaluation of the toxicity of particulate materials: I. Model compounds and metal-coated fly ash

Data are presented which detail the effects of model particulate compounds and fly ash particles on rabbit alveolar macrophage (RAM) and Chinese hamster ovary (CHO) cells. Silica, silicic acid, titanium dioxide, and size-fractionated (0–2, 2–5, and 5–8 μm) fly ash particles with and without coatings of nickel, lead, or cadmium oxides were the experimental particles. Silica was the most toxic particle studied. Cell viability and ATP in the RAM assay and colony survival in the CHO assay showed an almost identical response to silica and silicic acid. Titanium dioxide particles were relatively inert in the RAM and CHO systems, although a pronounced loss of ATP was observed in cells exposed in serum-free medium. Uncoated fly ash was relatively nontoxic in the RAM system when assayed by measurement of cell number and viability, ATP, and total protein. However, toxicity of the uncoated particles was demonstrated in the CHO clonal assay. The number of colonies formed at 1000 μg/ml particulate was reduced to 10.6, 28.5, and 82.2% of the control for the 0 to 2, 2 to 5-, and 5 to 8-μm size ranges. Nickel oxide-coated fly ash was more cytotoxic than the uncoated particles in both the RAM and CHO cell systems. Toxicity of NiO was similar to that obtained for the NiO-coated fly ash although the weight percentage of NiO in the ash was only 3%, suggesting that the particles enhanced toxicity. The lead oxide-coated fly ash was even more toxic than the nickel-coated particles; these particles were used to explore the effect of serum concentration on toxic responses. Cellular ATP was strongly affected in macrophages exposed in serum-free media and treated with PbO-coated fly ash; ATP ranged from 20 to 200 times less than that for the corresponding uncoated fly ash or untreated control. Nickel and lead did not dissociate from the fly ashes into the biological media. However, cadmium was rapidly released from the cadmium oxide-coated fly ash and provided an excellent model for study of the dissociation of toxic compounds from particle surfaces. The rate of dissociation of the metal was correlated with loss of ATP in RAM cultures. Cell numbers were unaltered after treatment with the CdO-coated fly ash as reported previously for soluble cadmium. The CdO-coated fly ash was considerably more toxic than would have been predicted on the basis of the amount of soluble cadmium released into the medium, also indicating that the association of the metal oxide with the fly ash enhanced toxicity.     

Mobility and contamination assessment of mercury in coal fly ash, atmospheric deposition, and soil collected from Tianjin, China

Samples of class F coal fly ash (levels I, II, and III), slag, coal, atmospheric deposition, and soils collected from Tianjin, China, were analyzed using U.S. Environmental Protection Agency (U.S. EPA) Method 3052 and a sequential extraction procedure, to investigate the pollution status and mobility of Hg. The results showed that total mercury (HgT) concentrations were higher in level I fly ash (0.304 μg/g) than in level II and level III fly ash and slag (0.142, 0.147, and 0.052 μg/g, respectively). Total Hg in the atmospheric deposition was higher during the heating season (0.264 μg/g) than the nonheating season (0.135 μg/g). Total Hg contents were higher in suburban area soils than in rural and agricultural areas. High HgT concentrations in suburban area soils may be a result of the deposition of Hg associated with particles emitted from coal-fired power plants. Mercury in fly ash primarily existed as elemental Hg, which accounted for 90.1, 85.3, and 90.6% of HgT in levels I, II, and III fly ash, respectively. Mercury in the deposition existed primarily as sulfide Hg, which accounted for 73.8% (heating season) and 74.1% (nonheating season) of HgT. However, Hg in soils existed primarily as sulfide Hg, organo-chelated Hg and elemental Hg, which accounted for 37.8 to 50.0%, 31.7 to 41.8%, and 13.0 to 23.9% of HgT, respectively. The percentage of elemental Hg in HgT occurred in the order fly ash?>?atmospheric deposition?>?soils, whereas organo-chelated Hg and sulfide Hg occurred in the opposite order. The present approach can provide a window for understanding and tracing the source of Hg in the environment in Tianjin and the risk associated with Hg bioaccessibility.     

Cytokinetic and morphological changes in the lungs and lung-associated lymph nodes of rats after inhalation of fly ash

Fischer-344 rats (male and female) were exposed to 36 mg/m³ of fluidized bed coal combustion fly ash or sham-exposed for 7 hr/day, 5 days/week for 4 weeks, and sacrificed after 2 or 4 weeks of exposure and at 2, 22, and 42 weeks after the end of exposure. Animals were injected with tritiated thymidine 2 hr before sacrifice and autoradiographs prepared from 1-μm sections of lung and lymph node tissue embedded in glycol methacrylate plastic. Differences in labeling indices of pulmonary epithelial cells, alveolar macrophages, airway epithelial cells, and cells of the lung-associated lymph nodes between the exposed and control animals were maximal after 2 and 4 weeks of exposure. Labeling indices for lung epithelial cells were about the same in control and exposed animals at 2, 22, and 42 weeks after the end of exposure. However, these values were elevated relative to earlier control levels. In contrast, morphological changes in the fly ash-exposed animals were most prominent after the end of the exposure. These changes included thickening of the alveolar walls, clusters of particle-filled macrophages in the alveolar region, and perivascular inflammation. Additionally, there were small granulomas in the alveolar region at 42 weeks after the end of exposure. Granulomas were also formed in the lung-associated lymph nodes and bronchus-associated lymphoid tissue. We conclude that the inhalation of fly ash alone had little detrimental effect upon the rat lung. However, the increases in proliferation indicate the potential for fly ash combined with a carcinogen to enhance the carcinogen's effect.     

Effect of Fly Ash Deposition on Photosynthesis,Growth and Yield of Rice

An experiment was conducted to assess the effect of fly ash deposition without and with (0.25, 0.50, 1.0 and 1.5 g m^?2 day^?1) foliar dusting on the photosynthesis, stomatal conductance, transpiration, leaf temperature, albedo and productivity of rice. Dusting of 0.5 g m^?2 day^?1 fly ash and above significantly reduced the photosynthesis, stomatal conductance, transpiration and albedo. Panicle initiation and flowering stages were more influenced by the fly ash deposition as compared to active tillering stage. At higher rates of fly ash deposition, all growth and yield parameters were significantly influenced due to increased heat load and reduced intercellular CO₂ concentration. A significant reduction of 12.3, 15.7 and 20.2 % in grain yield was recorded over control when fly ash was dusted at 0.5, 1.0 and 1.5 g m^?2 day^?1, respectively.     

Environmental and human exposure to soil chlorinated and brominated polycyclic aromatic hydrocarbons in an urbanized region

Nine chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/BrPAHs) and five parent polycyclic aromatic hydrocarbons (PAHs) were measured in urban surface soil and fly ash samples collected from Shenzhen, south China in winter 2010. The concentrations of total Cl/BrPAHs and PAHs in soil ranged from below the reporting limit to 142 ng/g and from 4.34 to 158 μg/g, respectively, and in fly ash they ranged from 17.7 to 19.5 ng/g and 26.1 to 28.3 μg/g, respectively. Concentrations of Cl/BrPAHs and parent PAHs were not significantly correlated with each other in soil or in fly ash, suggesting that Cl/BrPAHs were formed mainly by mechanisms other than direct halogenation of parent PAHs. Estimated mass inventories of 2-BrFlu varied from 68.1 kg in commercial land to 669 kg in countryside land, the highest among all Cl/BrPAHs. Loss fluxes via soil erosion accounted for only small proportions of total soil mass inventories of Cl/BrPAHs. Average daily human intake via soil ingestion decreased with increasing age, with 2-BrFlu as the main contributor. Children of 0 to 8 years old were the most sensitive subgroup (13.7 pg/kg body wt/d for total Cl/BrPAHs), and females were more sensitive than males in the same age group. The mean dioxin-like toxic equivalency quotient (TEQ) concentration of total Cl/BrPAHs (0.008 ng-TEQ/g) was lower in soil than in fly ash (0.06 ng-TEQ/g). Conversely, the mean TEQ concentration of total parent PAHs (2.23 ng-TEQ/g) was higher in soil than in fly ash.     

Comparative pulmonary fibrogenic potential of selected particles

The comparative intrapulmonary fibrogenic potential of a number of chemically and physically characterized ashes and dusts was studied. Sprague-Dawley rats were exposed through intratracheal instillation to 5, 15, or 45 mg of stack-collected coal fly ash, electrostatic precipitator hopper-collected coal fly ash, bag-house filter-collected coal-oil mixture fly ash, Dowson and Dobson quartz, heated montmorillonite clay, and Mt. St. Helens volcano ash. Following a 3-month postexposure period, the animals were killed and subjected to histological examination. Some fibrosis was produced by all the ashes. However, the effects differed both qualitatively and quantitatively among the various exposure groups. The most severe fibrosis was found in the quartz-treated animals, followed in order of intensity by the heated clay, volcano, ash, hopper coal ash, stack coal ash, and coal-oil mixture ash. No effects were found in the saline-exposed control rats.     

Chronic inhalation exposure of hamsters to nickel-enriched fly ash

Hamsters were chronically exposed to ～70 μg/liter respirable nickel-enriched fly ash (NEFA) aerosol, ～17 μg/liter NEFA, or ～70 μg/liter fly ash (FA) for up to 20 months. A control group received sham exposures. The NEFA particles of respirable size contained approximately 6% nickel, compared to about 0.3% for FA. Five hamsters/group were sacrificed after 4, 8, 12, or 16 months of exposure. An additional five hamsters/group were withdrawn from exposure at the same intervals for lifelong observations. Exposures to NEFA had no significant effect on body weight and life span of the animals although heavy deposits of NEFA in the lungs were demonstrated. However, lung weights of the high NEFA- and of the FA-exposed animals were significantly higher than those of the low-NEFA group and the controls, and mean lung volumes were significantly larger for the high-NEFA group and the FA group than for the low-NEFA group and the controls. Dust was deposited (anthracosis) in the lungs of all exposed hamsters. Incidence and severity of interstitial reaction and bronchiolization were significantly higher in the dust-exposed groups than in the sham-exposed controls. The severity of anthracosis, interstitial reaction, and bronchiolization was significantly lower in the low-NEFA group than in the high-NEFA and FA groups. While two malignant primary thorax tumors were found in two hamsters of the high-NEFA group, no statistically significant carcinogenesis was observed. Of the exposure-related changes, only anthracosis decreased after withdrawal from exposure. Pulmonary nickel burdens after 20 months of exposure suggest that the pulmonary clearance rate was slower in the high-NEFA group than in the low-NEFA group.     

Effects of lignite fly ash particulates and soluble components on the interferon system

Induction of interferon by influenza virus was depressed by approximately 50% when mammalian (LLC-MK₂) cell monolayers were pretreated with lignite fly ash. The presence of fly ash, however, did not impair the ability of exogenous interferon to confer antiviral cellular resistance. Influenza virus multiplication in cell monolayers pretreated with fly ash attained a twofold higher level of growth than that noted in normal cell monolayers. This was related to suppression of viral interferon induction by fly ash. Whereas aqueous extracts of fly ash had no adverse effect on interferon induction, extractions of fly ash by either polar or nonpolar solvents, by horse serum with or without EDTA (a metal chelator), and fractionation of serum extracts yielded corresponding compounds, most likely organic and inorganic, that were antagonistic to viral interferon induction. Residual fly ash particulates after extraction by horse serum with EDTA were still capable of inhibiting viral induction of interferon. These findings indicate that several soluble components inherent to lignite fly ash and the particulate matrix per se may modify, independently or in concert, cellular defense behavior. Neither polar, nonpolar, nor horse serum extracts of lignite fly ash, however, showed mutagenic activity as determined by the Salmonella histidine reversion assay. Removal of cell-membrane-bound sialic acid (N-acetylneuraminic acid) by neuraminidase or pretreatment of lignite fly ash with sialic acid abolished the adverse activity of fly ash on viral interferon induction. This suggests that the interaction of cell-membrane-bound sialic acid residue with fly ash particulates may be involved in the altered state of cellular behavior described in response to viral induction of interferon.     

Metal Accumulation and Health Effects in Raccoons (Procyon lotor) Associated with Coal Fly Ash Exposure

Approximately 5.4 million cubic yards of coal fly ash and water spilled into the Emory River embayment of Watts Bar Reservoir in east Tennessee on Dec 22, 2008. Raccoons were collected in 2009 and 2010 from the spill site (10/y) and unexposed areas (5/y) to determine whether metals and metalloids were accumulating in raccoons and if any negative health effects resulted from exposure to the spilled coal fly ash. Tissues were analyzed from each animal to determine the concentrations of 26 metals/metalloids. Complete blood cell counts (CBC), plasma biochemistry panels, and histopathology of select tissues also were performed. Results were analyzed by year and exposure status. Although significant differences were present in some tissues for some metals/metalloids, only arsenic in hair, iron in muscle, nickel in hair, selenium in hair and muscle, strontium in hair, and vanadium in hair and liver were increased in spill site animals (one or both years) compared with unexposed animals. No clinically important differences were observed between groups regarding CBC or plasma biochemistry analyses. Lesions were observed on histopathology in some tissues, but there was no difference in the prevalence of lesions between spill site and unexposed animals. There does not seem to be any important accumulation of metals/metalloids or negative health effects in raccoons associated with exposure to coal fly ash compared with unexposed animals.     

Bioavailability of 1-nitropyrene from model coal fly ash and its uptake by alveolar macrophages

Alveolar macrophage cultures exposed to coal fly ash vapor-coated with 1-nitropyrene were used as a model system to study the bioavailability and the uptake of a nitroaromatic hydrocarbon from coal combustion emissions. Initially, 1-nitropyrene-coated fly ash and uncoated fly ash were examined for cytotoxicity using rabbit alveolar macrophages and for mutagenicity in the Salmonella typhimurium plate incorporation assay. The results were compared to determine the effects of vapor deposition. The distribution and recovery of 1-nitropyrene from macrophage cultures treated with coated fly ash were determined by using a reverse-phase high-performance liquid chromatography-fluorescence method. 1-Nitropyrene alone was not very toxic, nor did vapor deposition of 1-nitropyrene onto coal fly ash significantly affect the toxicity of the fly ash. Most toxicity resulted from the original, uncoated fly ash particles. 1-Nitropyrene after being coated onto the particles was bioavailable in agar and aqueous culture medium. The coated fly ash showed mutagenic activity when the particles were tested directly; the uncoated fly ash did not show mutagenic activity. 1-Nitropyrene recovery from alveolar macrophage cultures exposed to the coated fly ash diminished as cell number increased. The rate of 1-nitropyrene loss was 2.7 ng/10(6) macrophages for medium and 4.1 ng/10(6) macrophages for the whole culture. The mutagenic activity recovered from these macrophage cultures also decreased with increasing cell number.     

The utilization of the rabbit alveolar macrophage and Chinese hamster ovary cell for evaluation of the toxicity of particulate materials: II. Particles from coal-related processes

Rabbit alveolar macrophage (RAM) and Chinese hamster ovary (CHO) cells were used in in vitro tests to evaluate the toxicity of particulate effluents from coal gasification, fluidized-bed combustion, and conventional coal combustion. Evaluation of the cytotoxicity of nine samples from coal energy-related processes showed that the sensitivity of the RAM assay was improved substantially when the test was conducted in serum-free media. A linear relationship was observed between percentage cell viability and ATP level in the particletreated cultures. In the RAM assay without serum the slope of the line was 1.0, which provided strong evidence that the mechanism of toxicity was similar in reducing cell viability and ATP. The cytotoxicity of the coal-related particles in the CHO clonal assay showed that the system was approximately equivalent to the RAM assay without serum. Conventional coal combustion fly ash (<3 μm) was the most toxic of the coal-related particles in the RAM and CHO system. Fluidized-bed combustion fly ash from a cyclone catch and fine (<3 μm) particles from the flue gas were also toxic in both cellular assays. Particles from the coal gasification process were the least cytotoxic in these studies.     

Formation of Polychlorinated Naphthalenes,Dibenzo-<Emphasis Type="Italic">p</Emphasis>-Dioxins,Dibenzofurans, Biphenyls,and Organochlorine Pesticides in Thermal Processes and Their Occurrence in Ambient Air

Mono- through octachlorinated naphthalenes (PCNs) were measured in start-up, steady operation, and shutdown of machinery operation flue gas and fly ash generated during different stages of MSWI and other incineration thermal processes. Besides, electroprecipitator fly ash (EP-ash) was dechlorinated using the Hagenmeier process and analyzed for congener profiles. In addition to PCNs, polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), and major organochlorine pesticides were determined in ambient air samples from three different sites of western Japan in the summer and winter of 1992. The PCNs from flue gas contained 15,000, 4300, and 13,000 ng/m³ during start-up, steady operation, and shutdown conditions, respectively. Whereas fly ash contained 470, 370, and 1400 ng/g PCNs under start-up, steady operation, and shutdown condition, respectively. The dechlorination process reduced PCN concentrations considerably. Concentrations of PCNs and PCDD/PCDFs in air samples collected in winter were slightly higher than in summer. PCBs, organochlorine pesticides such as chlordanes, DDTs, and HCHs were higher in summer air samples. WHO toxic equivalency (WHO-TEQ) concentrations in air samples were 0.3–0.9 pg/m³ for PCDD/DFs and 0.029–0.31 pg/m³ for dioxin-like PCBs.     

Solubility of Trace Elements and Heavy Metals from Stabilized Sewage Sludge by Fly Ash

Stabilized sewage sludge (SS) by fly ash (FA) and alkaline mine tailing as artificial soil, to be applied on the ecological rehabilitation at mining junkyard, offers a potential viable utilization of the industrial by-product, as well as solves the shortage of soil resource in mine area. In this study, trace element and heavy metal soil solution concentrations arising from fly ash, sewage sludge, mine tailing, and artificial soil mixtures were investigated in a laboratory incubation. It was found that total Cd, Pb, and Zn contents in artificial soils were significantly lower than the control standards for pollutants in sludges from agricultural use (GB 4284-84). Soil solution Cd and Pb concentrations were obviously reduced by mixing sewage sludge with alkaline fly ash. Initial soil solution Cd, Pb, and Zn concentrations in artificial soils were 1.773–14.672, 4.05–24.95, and 133–608 μg L⁻¹, respectively, and after 35-days incubation, soil solution Cd, Pb, and Zn concentrations gradually decreased and were approaching control levels by the end of the experiment, and finial soil solution were decreased to 0.037–0.365, 2.12–7.34, and 29–509 μg L⁻¹, respectively.     

Leaching of polychlorinated dibenzo-p-dioxins and dibenzofurans in fly ash from municipal solid waste incinerators to a water system

In order to predict how much polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) are leached from fly ash by rain water when fly ash is disposed, leaching of PCDDs/Fs from a fly ash obtained from a municipal solid waste incinerator (MSWI) was investigated by packing the ash in a column and eluting with water. In the beginning of the elution, PCDDs/Fs associated with water-soluble particulates in the ash were eluted, whereas in the latter half, those associated with water slightly soluble particles were eluted, judging from the comparison of PCDDs/Fs in eluate fractions with those transferred to solutions from the original ash by stepwise batch methods with water and 2N hydrochloric acid.The amounts of PCDDs/Fs eluted from the ash column were 2.9% and 1.7% of those extracted from the original ash, respectively, while large amounts of PCDDs/Fs were contained in the fly ash in the column after the elution, suggesting that PCDDs/Fs in water-insoluble particulates of the ash would not be eluted by water.     

Effects of lignite fly ash particulates and soluble components on the interferon system

Induction of interferon by influenza virus was depressed by approximately 50% when mammalian (LLC-MK2) cell monolayers were pretreated with lignite fly ash. The presence of fly ash, however, did not impair the ability of exogenous interferon to confer antiviral cellular resistance. Influenza virus multiplication in cell monolayers pretreated with fly ash attained a twofold higher level of growth than that noted in normal cell monolayers. This was related to suppression of viral interferon induction by fly ash. Whereas aqueous extracts of fly ash had no adverse effect on interferon induction, extractions of fly ash by either polar or nonpolar solvents, by horse serum with or without EDTA (a metal chelator), and fractionation of serum extracts yielded corresponding compounds, most likely organic and inorganic, that were antagonistic to viral interferon induction. Residual fly ash particulates after extraction by horse serum with EDTA were still capable of inhibiting viral induction of interferon. These findings indicate that several soluble components inherent to lignite fly ash and the particulate matrix per se may modify, independently or in concert, cellular defense behavior. Neither polar, nonpolar, nor horse serum extracts of lignite fly ash, however, showed mutagenic activity as determined by the Salmonella histidine reversion assay. Removal of cell-membrane-bound sialic acid (N-acetylneuraminic acid) by neuraminidase or pretreatment of lignite fly ash with sialic acid abolished the adverse activity of fly ash on viral interferon induction. This suggests that the interaction of cell-membrane-bound sialic acid residue with fly ash particulates may be involved in the altered state of cellular behavior described in response to viral induction of interferon.     

Lipid peroxidation and oxidative status compared in workers at a bottom ash recovery plant and fly ash treatment plants

Fly ash and ambient emissions of municipal solid waste incinerators contain polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs), other organic compounds, metals, and gases. Hazardous substances such as PCDD/Fs, mercury vapors and other silicates, and the components of bottom ash and fly ash elevate the oxidative damage. We compared oxidative damage in workers exposed to hazardous substances at a bottom ash recovery plant and 3 fly ash treatment plants in Taiwan by measuring their levels of plasma malondialdehyde (MDA) and urine 8-hydroxydeoxyguanosine (8-OH-dG). Significantly higher MDA levels were found in fly ash treatment plant workers (3.20 microM) than in bottom ash plant workers (0.58 microM). There was a significant association between MDA levels in workers and their working environment, especially in the fly ash treatment plants. Levels of 8-OH-dG varied more widely in bottom ash workers than in fly ash workers. The association between occupational exposure and 8-OH-dG levels may be affected by the life style of the workers. Because more dioxins and metals may leach from fly ash than from bottom ash, fly ash treatment plant workers should, as much as possible, avoid exposing themselves to fly ash.     

Dose-related effect of fly ash on edaphic properties in laterite cropland soil

Short-term laboratory and field studies showed dose-based effect of coal fly ash on chemical and microbial properties of laterite cropland soil. Sandy loam soil mixed with farmyard manure (10% w/w) and amended with fly ash at 5%, 10%, 20%, 40% w/w (50-400 t ha⁻¹) was incubated in the laboratory and added to field plots. The pH, EC, PO₄, Ca and Na of soil increased with dose and time, but OC, NO₃ and K decreased. There was temporary inhibition of bacteria, fungi and actinomycetes populations at 5% and 10% doses, but 20% and 40% were harmful. Activities of major soil enzymes declined at higher doses. Amylase, cellulase and invertase recovered in 5% and 10%, these doses did not affect dehydrogenase but benefited phosphatase and arylsulphatase activities. The above assessments showed that up to 100 t ha⁻¹ fly ash is apparently safe to microbial characteristics of tropical red laterite soil.