Gerald L. Fisher

Mutagenicity of airborne particles

The physical and chemical properties of airborne particles are important for the interpretation of their potential biologic significance as genotoxic hazards. For polydisperse particle size distributions, the smallest, most respirable particles are generally the most mutagenic. Particulate collection for testing purposes should be designed to reduce artifact formation and allow condensation of mutagenic compounds. Other critical factors such as UV irradiation, wind direction, chemical reactivity, humidity, sample storage, and temperature of combustion are important. Application of chemical extraction methods and subsequent class fractionation techniques influence the observed mutagenic activity. Particles from urban air, coal fly ash, automobile and diesel exhaust, agricultural burning and welding fumes contain primarily direct-acting mutagens. Cigarette smoke condensate, smoke from charred meat and protein pyrolysates, kerosene soot and cigarette smoke condensates contain primarily mutagens which require metabolic activation. Fractionation coupled with mutagenicity testing indicates that the most potent mutagens are found in the acidic fractions of urban air, coal fly ash, and automobile diesel exhaust, whereas mutagens in rice straw smoke and cigarette smoke condensate are found primarily in the basic fractions. The interaction of the many chemical compounds in complex mixtures from airborne particles is likely to be important in determining mutagenic or comutagenic potentials. Because the mode of exposure is generally frequent and prolonged, the presence of tumor-promoting agents in complex mixtures may be a major factor in evaluation of the carcinogenic potential of airborne particles.

Crystalline components of stack-collected, size-fractionated coal fly ash

As part of a program to characterize the fly ash which is emitted by coal-fired power plants, qualitative identification and quantitative estimation of the crystalline components of four size-fractionated and one unfractionated fly ash sample are reported. Although fly ash is mostly amorphous to X-rays, the presence of small amounts of quartz, hematite, mullite, gypsum, magnetite, and ferrite have been reported (1-3). However, quantitative determinations of these mineral phases have not been reported, nor have the crystalline phases been studied as a function of particle size. A knowledge of the Crystalline phases is of importance in the consideration of the potential health effects of inhaled particles. Because of the refractory nature of the quartz, mullite, and magnetite phases, these materials will have long residence times in the pulmonary region of the respiratory tract if they are deposited there ( 4 ) . Therefore, it is important to know the particle size distribution and concentrations of these materials in stack-collected coal fly ash. Furthermore, it is generally recognized that crystalline siliceous materials are more toxic than amorphous compounds of the same composition. Such particles are known to have significant effects on lung cells ( 5 ) and appear to be important toxicants to the pulmonary macrophage, the primary effector cell for lung immunosurveillance. Magnetite may also be a hazard to health because of its ability t o occlude biologically active transition-metal ions such as Mn and Ni by isomorphous substitution in the spinel crystal lattice (2). Magnetite could thus act as a slow release carrier agent for toxic elements. For this reason we have performed analyses of the magnetic phase for those metals which are likely to be associated with the magnetic fraction of the ash. The crystalline phases are important in determining the physical and chemical properties of the ash. Data on the crystalline phases may be useful in developing methods for resource recovery from, utilization of, and disposal of the ash (2). The mechanisms of formation of the various crystalline

Chemical speciation of elements in stack-collected, respirable-size, coal fly ash

The data reported in this paper effectively complete the description of the chemical speciation of the elements in a set of four stack-collected coal fly ash samples which have been used extensively in the determination of the biological effects of coal fly ash. The association of elements with the aluminosilicate glass or surface salts, the association of cations and anions of the surface of ash particles, and the oxidation states of nonmetal and transition metals are discussed. 27 references.

Adult peripheral lung organ culture--a model for respiratory tract toxicology.

This report describes procedures to culture 1- to 2-mm-thick cross sections of lung lobes for periods of 4 to 6 weeks. Normal morphologic and macromolecular composition are maintained. Previous attempts to maintain adult peripheral lung cultures for periods beyond 7-10 days or to examine respiratory disorders in vitro other than acute changes have been generally unsuccessful. Eight different, supplemented, serum-free media, mixed with heated liquid agarose were infused into the airways of hamster and rat lungs. Cross sections were explanted onto squares of porous surgical packing material, placed in medium, and incubated for 4 to 6 weeks. The ability of each medium to maintain normal lung was assessed microscopically by quantitative image analysis and by biochemical analyses. The optimal medium formulation for each species is described. The adult peripheral lung culture system may provide toxicologists with a unique model for mechanistic and safety evaluations of potential lung toxicants.

In vitro models of lung toxicity

In vitro assays that emphasize cellular components critical to the host defense system have been developed to evaluate pulmonary toxicity and define deleterious changes in parenchymal cell populations. Assays that employ pulmonary alveolar macrophages (PAM) have demonstrated good correlation between macrophage toxicity and pulmonary fibrogenicity for many inorganic compounds. The PAM assays provide simple and inexpensive screens of potential respiratory tract toxicity. Many investigators screen chemicals for their ability to alter the mucosal epithelial cell conducting airways by performing tracheal organ cultures. The tracheal assays have also provided useful screens for Vitamin A analogues required for epithelial cell differentiation. Most recently, in vitro respiratory tract models have been extended to include whole-lung explants, an approach that allows for development of fibrosis and epithelial cell toxicity after in vitro exposure to inorganic and organic fibrogens. The whole-lung explant system appears to duplicate the in vivo response to a variety of lung toxins, including bleomycin, silica, and crocidolite asbestos. Together, these assays provide a description of potential toxicity to key components of the lung, emphasizing the pulmonary macrophage, conducting airways, and alveolar septae. It is expected that continued research in these models will enhance their predictive abilities and utility in risk assessment.

Morphological and biochemical features of elastase-induced emphysema in strain AJ mice☆

Elastase-induced animal models of pulmonary emphysema are potentially useful to study the physiological, anatomical, and biochemical injuries associated with emphysema. After the endotracheal instillation of porcine pancreatic elastase (0.15 or 0.30 mg elastase per 100 g body weight) into strain A/J mice, selected biochemical and morphometric indices od lung damage were examined. Elastase produced extensive air space enlargement without appreciable mortality. Lesions involving the lung parenchyma distal to the terminal bronchioles were observed within 2 weeks and possessed features resembling panlobular and centrilobular emphysema. Morphometric analyses of emphysema indicated that after the acute phase of tissue damage and repair, the lesions stabilize without further deterioration of alveolar structure. Increased lung elastin synthesis was noted following endotracheal elastase, resulting in lung elastin levels 30% higher than controls 8 weeks after treatment. Minimal alterations to lung DNA and protein levels indicated that elastase produced specific lung lesions exclusive of inflammation and edema.

Trace element interactions affecting pulmonary macrophage cytotoxicity

Effluents from the smokestacks of powerplants contain respirable particles that are enriched with a variety of biologically active trace elements. To determine the relative toxicity of trace elements in coal fly ash, the effects of selected compounds, alone and in combination, were evaluated in cultures of pulmonary alveolar macrophages. The inorganic compounds studied were ZnO, Na2SeO3, V2O5, NaAsO2, Mn3O4, and Ni3S2. Vanadium pentoxide was the most cytotoxic compound while selenium was the least toxic (approximately 100-fold less toxic than vanadium). After dose-response curves for each element were established, interactions between various compounds were studied by coexposure to trace elements at different concentrations. Selenium was completely antagonistic to the toxic effects of vanadium and slightly antagonistic to arsenic. In contrast to selenite, sulfite, a moiety with a similar redox potential, was not antagonistic to vanadium toxicity. Zinc was weakly antagonistic to the in vitro effects of nickel. No other chemical combinations displayed antagonistic, synergistic or additive effects on the function of the cultured macrophages.

Assessment of the teratogenicity of ammonium vanadate using Syrian golden hamsters

Abstract The exposure of pregnant Syrian golden hamsters to ammonium vanadate from Days 5 through 10 of gestation resulted in a statistically significant increase in skeletal anomalies and a decrease in the male:female fetal sex ratio. Skeletal anomalies included micrognathia, supernumerary ribs, and alterations in sternebral ossification. Although not statistically significant, external anomalies included meningocoele, one fetus with multiple anomalies, and the presence of a molar pregnancy. Soft tissue anomalies did not differ significantly among groups but included hydronephrosis/hydroureter and kidney dysplasia. The small numbers of malformed offspring and the lack of a clear-cut dose—response did not allow a definitive assessment of the teratogenicity of ammonium vanadate.

Pulmonary clearance of intratracheally administered 63Ni3S2 in strain AJ mice

The pulmonary clearance of particulate 63Ni3S2 was evaluated in strain A/J mice following the intratracheal instillation of 3 microCi of 63Ni3S2 (1.66 micron, mass median diameter). Lung and tissue burdens were determined from serially sacrificed animals using scintillation counting techniques. Lung clearance over the 35-day observation period could be separated into two distinct components with initial and final phase biological half-times corresponding to 1.2 and 12.4 days, respectively. Radioactivity was detected in the blood, liver, kidney, and femur within 4 hr, and was eliminated at rates comparable to that in the lung. Excretion involved primarily urinary (60% of dose eliminated) but also fecal (40% of dose eliminated) pathways. The data are consistent with the relatively rapid translocation, solubilization, and elimination of particulate 63Ni3S2 from the body.

Characterization of microbial mutagens in complex samples—methodology and application

Methodologies for characterization of mutagens in complex mixtures have been reviewed. The methods discussed include successive fractionation with various solvents, combinations of chemical fractionation and bio‐assay directed analyses and separation with in situ testing using thin layer chromatography or other separation techniques. In all cases the discussions are limited to the Ames Salmonella assay as detection method for mutagenicity. Particular problems in testing complex samples such as bacterial toxicity, synergistic or antagonistic effects are also discussed. Applications of the methods are reviewed. These applications include environmental samples such as airborne particles, water pollutants, and consumer products.