Robert L. Carpenter

Comparative inhalation toxicity of nickel subsulfide to F344/N rats and B6C3F1 mice exposed for 12 days.

Groups of F344/N rats and B6C3F1 mice were exposed to aerosols of nickel subsulfide (Ni3S2) 6 hr/day for 12 days not including weekends. Actual exposure concentrations were within 3% of target (target = 10.0, 5.0, 2.5, 1.2, 0.6, and 0.0 mg Ni3S2/m3). Nickel lung burdens of exposed rats and mice increased linearly with exposure concentration. Two male rats and all mice exposed to 10.0 mg Ni3S2/m3 died before the end of the exposures. Exposure to Ni3S2 had no effect on the natural killer cell activity of mouse spleen cells. Lesions in rats and mice related to inhalation of Ni3S2 were found in the nasal epithelium, lung, and bronchial lymph nodes. The most extensive lesions were found in the lung and included necrotizing pneumonia. Emphysema developed in rats exposed to 5.0 or 10.0 mg Ni3S2/m3, while fibrosis developed in mice exposed to 5.0 mg Ni3S2/m3. Degeneration of the respiratory epithelium and atrophy of the olfactory epithelium of the nose occurred in rats exposed to as low as 0.6 mg Ni3S2/m3 and mice exposed to 1.2 mg/m3. Results indicate that inhalation exposure of rats and mice to Ni3S2 aerosol concentrations near the current threshold limit value (TLV) for nickel compounds (1 mg/m3 for Ni metal and roasting fume and dust and 0.1 mg/m3 as Ni for soluble compounds) can produce lesions in the respiratory tract. Atrophy of lymphoid tissues (spleen, thymus, and bronchial lymph nodes) was found in animals of the highest exposure concentration. Degeneration of the testicular germinal epithelium was also observed in mice and rats that survived 5.0 or 10.0 mg/m3 exposure concentrations.

Comparative inhalation toxicity of nickel sulfate to F344/N rats and B6C3F1 mice exposed for twelve days.

Groups of F344/N rats and B6C3F1 mice were exposed to aerosols of nickel sulfate hexahydrate (NiSO4.6H2O) 6 hr/day for 12 days to determine the short-term inhalation toxicity of this compound. Target exposure concentrations were 60, 30, 15, 7, 3.5, and 0 mg NiSO4.6H2O/m3. Endpoints evaluated included clinical signs, mortality, quantities of Ni in selected tissues, effect on mouse resistance to tumor cells, and pathological changes in tissues of both rats and mice. All mice exposed to 7 mg NiSO4.6H2O/m3 or greater and 10 rats exposed to 15 mg NiSO4.6H2O/m3 or greater died before the termination of exposures. Quantities of Ni remaining in lungs of rats at the end of the exposure were independent of exposure concentration. Lung burdens of Ni in mice were approximately one-half that in lungs of rats. Exposure of female mice to 3.5 mg NiSO4.6H2O/m3 had no effect on resistance to tumor cells as determined by spleen natural killer cell activity. Histopathological changes were seen in tissues of rats and mice exposed to as low as 3.5 mg NiSO4.6H2O/m3. Lesions related to NiSO4.6H2O exposure occurred in lung, nose, and bronchial and mediastinal lymph nodes. Results indicated that exposure of rats and mice to amounts of NiSO4.6H2O aerosols resulting in Ni exposure concentrations only eight times greater than the current threshold limit value for soluble Ni (0.1 mg/m3) for as little as 12 days can cause significant lesions of the respiratory tract.

Evaluation of Tenax-GC and XAD-2 as polymer adsorbents for sampling fossil fuel combustion products containing nitrogen oxides.

Tenax-GC and Amberlite XAD-2 are porous polymer adsorbents used to sample organic vapors in effluents from fossil fuel combustion technologies. Experiments determining the efficacy of the two adsorbents are summarized. Gas chromatography-mass spectrometry analysis indicates that Tenax-GC would be more suitable than XAD-2 for the sampling of stack effluents from fossil fuel combustion.

Respirable aerosols from fluidized bed coal combustion. 3. Elemental composition of fly ash

Trace element constituents in fly ash from an experimental atmospheric fluidized bed combustor (AFBC) are reported and compared with pulverized coal combustor (PCC) data and those from other fluidized bed combustors. Bulk and size-separated particles were collected and analyzed using spark source mass spectrometry. Fluidized bed combustion ash was similar to PCC ash in minor and trace element composition, but AFBC ash showed less size dependence of elemental composition. Bulk particle elemental composition varied with sampling position within the effluent stream. Penetration of elements through each cleanup stage and elemental enrichment were a function of the cleanup stage and the element under consideration.

Comparative lung immunotoxicity of inhaled quartz and coal combustion fly ash

Some inhaled particles that are deposited in the terminal airways and alveoli clear to the lung-associated lymph nodes, and insoluble particles have a long half-life in these tissues. Because the lung-associated lymph nodes are essential in the induction of immunity after lung immunization, the accumulation of inhaled particles in these tissues could alter immune responses that develop after lung immunization. This study evaluated the effects of inhaled insoluble fly ash particles or alpha quartz on the immune functions of lung-associated lymph nodes. F344 rats were exposed for 20 days by inhalation of fly ash from a fluidized bed combustor (FBC) or a pulverized coal combustor (PCC). Rats were similarly exposed to quartz particles (Min-U-Sil). Control rats were exposed to filtered air. Groups of ten exposed and ten control rats from each group were immunized by intratracheal instillation of 10(8) sheep red blood cells at 4, 6, 40, and 52 weeks after the start of exposures. The cellularity of the lung-associated lymph nodes and antibody-mediated immunity were evaluated at 7 days after immunization. Tissues from lung and lung-associated lymph nodes were taken for histopathology. The inhalation of FBC fly ash, PCC fly ash, and quartz particles all significantly increased the number of lymphoid cells in the lung-associated lymph nodes at each of the sacrifice times. However, FBC fly ash had no significant effect on antibody immunity, while both PCC fly ash and quartz caused suppression of antibody responses at 52 weeks after the start of exposure. Histopathology data showed that exposure to quartz and PCC fly ash caused significant cellular changes in lungs and lung-associated lymph nodes, while FBC fly ash had less effect. These data indicate that an acute exposure (20 days) to relatively insoluble particles significantly increased the cellularity of the lung-associated lymph nodes for up to 52 weeks after the start of the exposure, but the pulmonary toxicity of the particles inhaled appeared to influence the effects of the exposure on antibody immune responses.

High-temperature-high-pressure cascade impactor design, performance, and data analysis methods

Abstract A high-temperature-high-pressure, seven-stage cascade impactor has been designed, built, calibrated, and used to obtain size-classified samples of entrained fly ash from process streams of a pressurized low Btu coal gasifler. The cascade impactor was designed for an effective cutoff diameter (ECD) range of 12 μm down to about 0.5 μm aerodynamic diameter. Methods for calculating gas mixture viscosity, density, and mean free path have been developed and used to calculate impactor stage characteristics at operating temperatures and pressures for the gas mixture sampled. Process stream conditions were 400–700°C and 900–1370 kPa. The measured size distribution at stream conditions indicated a mass median aerodynamic diameter (MMAD) of 2.88 ± 0.47 μm with a geometric standard deviation (σg) of 2.35 ± 0.35.

Improvement of Aerosol Distribution in Whole-Body Inhalation Exposure Chambers

AbstractUniform distribution of aerosol concentration in inhalation exposure chambers is important in the conduct of inhalation experiments. Several factors, including aerosol size, degree of mixing, and chamber design, may influence the aerosol distribution in whole-body exposure chambers. We report distributions in two types of Hazleton exposure chambers for different aerosol size and degree of mixing. To increase the mixing, a small fan was placed inside the chamber Without the fan, the spatial variation increased with aerodynamic particle size and reached 12% and 46% for 3.1-μm particles in Hazleton H2000 and H1000 chambers, respectively With the fan, the spatial variation was reduced to between 4% and 6% for particles in the size range of 7.6–3.7 μm. These data were obtained in chambers containing cage units, but without animals. Similar results were obtained with animals in the chamber.

Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc

The relationship between the inhalation exposure concentration of talc and the resulting lung burdens and histologic lesions was studied using groups of 20 F344/Crl rats and 20 B6C3F mice (10 male and 10 female) exposed to one of three concentrations of asbestos-free talc for 6 hr/day, 5 days/week for 4 weeks. Controls were exposed to filtered air using the same schedule. The pulmonary retention of talc and the development of pulmonary pathology were evaluated. The mass median aerodynamic diameter (MMAD) of the talc aerosol was 3.0 microns with a geometric standard deviation (sigma g) of 1.9. The mean exposure concentrations for rats were 0, 2.3, 4.3, and 17 mg talc/m3. Lung burdens in rats averaged 0, 0.07, 0.17, and 0.72 mg talc/g lung after the 20-day inhalation exposure; thus, the amount retained in the lung per unit of exposure concentration increased with increasing concentration. Mean exposure concentrations for the mice were 0, 2.2, 5.7, and 20.4 mg of talc/m3, which resulted in lung burdens of 0, 0.10, 0.29, and 1.0 mg talc/g lung; thus, the relationship between exposure concentration and the amount retained in the lung was approximately constant. Lung burdens from this study were used to project lung burdens that would result from longer exposures of rodents and man. No clinical signs were observed in the rats or mice prior to sacrifice 24 hr after the last exposure day. Histologic alterations in lung tissue consisted of only a modest, diffuse increase of talc-containing, free macrophages within alveolar spaces in both rat and mouse groups exposed to the highest level of talc for 20 days. A model simulating chronic talc inhalation exposure of rats and mice predicted lung burdens of 2-3 mg talc/g lung (wet wt) if animals were exposed to 17 mg talc/m3 for 2 years, and deposition and clearance of talc were unchanged by continued exposure. A potential limitation in this modeling is that if clearance of talc is delayed by continued exposure, the accumulated talc lung burdens would be higher than those projected by the simulation model. Humans exposed to aerosols of respirable talc are projected to accumulate much higher lung burdens than would occur in rodents exposed to the same aerosol, because humans have a higher estimated deposition fraction and slower estimated clearance of the deposited talc dust. Equilibrium lung burdens of greater than or equal to 2 mg talc/g lung were predicted for human exposures at or near the TLV for talc.

Low Btu Coal Gas Combustion Emission Characteristics

Information presented in this paper is directed to individuals concerned with the emission characterization and control of process streams. Emissions from burning low Btu gas from an experimental gasifier were sampled and characterized. Both particulate and vapor samples were collected. Transmission electron micrographs showed that the particles were single droplets less than 1 μm in diameter. Size distributions of aerosols as measured by the electrical aerosol analyzer showed a bimodal distribution. Energy dispersive X-ray analysis and ion chromatography analyses indicated that SO4 -2 was the major component of the aerosol. This suggested that the combustion aerosol from low Btu gas may be sulfuric acid droplets or other sulfates produced from oxidation of H2S in the combustion process. Particulate mass loadings were estimated to be 0.1 and 0.0024 lb/106 Btu for H2S levels of 3600 and 500 ppm respectively. Some reduction of organic vapors in the combustion products was observed when the H2S level was red...

Use of a massive volume air sampler to collect fly ash for biological characterization

The report describes the modification of a massive volume air sampler (MVAS) to collect fly ash emissions from the stack mouth of an experimental fluidized bed combustor. High volume filter fly ash samples and laboratory size cascade impactor samples were simultaneously obtained to verify the operation of the MVAS. Due to the large quantity of size-classified fly ash it was possible to characterize its physicochemical and biological properties as a function of particle size. Results show that the bulk density of the FBC fly ash was independent of the particle size. Although the MVAS collects fly ash fractions with considerable overlap, the trend toward higher mutagenic activity in the smaller size fraction noted in previous studies of fly ash was present. As the MVAS does have a large capacity, relatively large quantities of ash can be collected within reasonable sampling times. With appropriate dilution even hot gas streams can be sampled at near ambient temperatures.