Particle Clearance and Histopathology in Lungs of F344/N Rats and B6C3F1 Mice Inhaling Nickel Oxide or Nickel Sulfate

The goals of this study were to (1)determine the effects ofrepeated inhalation of relatively insoluble nickel oxide (NiO)and highly soluble nickel sulfate hexahydrate (NiSO₄ 6H₂O) onlung particle clearance, (2)investigate the effects of repeatedinhalation of NiO or NiSO₄ on the pulmonary clearance of subsequentlyinhaled ⁸⁵Sr-labeled microspheres, (3)correlate the observedeffects on clearance with accumulated Ni lung burden and associatedpathological changes in the lung, and (4)compare responses inF344 rats and B6C3F₁, mice. Male F344/N rats and B6C3F₁ micewere exposed whole-body to either NiO or NiSO₄ 6H₂O 6 hr/day,5 days/week for up to 6 months. NiO exposure concentrationswere 0, 0.62, and 2.5 mg NiO/m for rats and 0, 1.25, and 5.0mg NiO/ m for mice. NiSO₄ 6H₂O/m³ exposure concentrations were0, 0.12, and 0.5 mg NiSO₄ 6H₂ for rats and 0, 0.25, and 1.0mg NiSO₄ 6H₂O/m³ for mice. After 2 and 6 months of whole-bodyexposure, groups of rats and mice were acutely exposed nose-onlyto 63 (NiO-exposed animals only), ⁶³NiSO₄ 6H₂O (Ni SO₄ 6H₂Oanimals only), or to ⁸⁵Sr-labeled polystyrene latex (PSL) microspheres(both NiO- and NiSO₄ 6H₂O-exposed animals) to evaluate lungclearance. In addition, groups of rats and mice were euthanizedafter 2 and 6 months of exposure and at 2 and 4 months afterthe whole-body exposures were completed to evaluate histopathologicalchanges in the left lung and to quantitate Ni in the right lung.Repeated inhalation of NiO results in accumulation of Ni inlungs of both rats and mice, but to a greater extent in lungsof rats. During the 4 months after the end of the whole-bodyexposures, some clearance of the accumulated Ni burden occurredfrom the lungs of rats and mice exposed to the lower, but notthe higher NiO exposure concentrations. Clearance of acutelyinhaled ⁶³NiO was also impaired in both rats and mice, withthe extent of impairment related to both exposure concentrationand duration. However, the clearance of acutely inhaled ⁸⁵SrPSL microspheres was not impaired. The repeated inhalation ofNiO resulted in alveolar macrophage (AM) hyperplasia with accumulationof NiO particles in both rats and mice, chronic alveolitis inrats, and interstitial pneumonia in mice. These lesions persistedthroughout the 4-month recovery period after the NiO whole-bodyexposures were terminated. In contrast, repeated inhalationof NiSO₄ 6H₂O did not result in accumulation of Ni in lungsof either rats or mice and did not affect the clearance of ⁶³NiSO₄6H₂Oinhaled after either 2 or 6 months of NiSO₄ 6H₂O exposure. Clearanceof the ⁸⁵Sr-labeled microspheres was significantly impairedonly in rats exposed to the microspheres after 2 months of exposureto NiSO₄ 6H₂O Histopathological changes in rats were qualitativelysimilar to those seen in NiO-exposed rats. Only minimal histopathologicalchanges were observed in NiSO₄ 6H₂O mice. These results suggestthat repeated inhalation of NiO at levels resulting in AM hyperplasiaand alveolitis may impair clearance of subsequently inhaledNiO. The potential effects of repeated inhalation of solubleNiSO₄ 6H₂O on the clear ance of subsequently inhaled poorlysoluble particles are less clear.     

The Immunotoxicity of Three Nickel Compounds following 13-Week Inhalation Exposure in the Mouse

The Immunotoxicity of Three Nickel Compounds following 13-WeekInhalation Exposure in the Mouse. HALEY, P. J. SHOPP, G. M.,BENSON, J. M, CHENG, Y.-S., BICE, D. E., LUSTER, M. I., DUNNICK,J. K., AND HOBBS, C. H. (1990). Fundam. Appl. Toxicol 15, 476–487.Groups of B6C3F₁, mice were exposed to aerosols of nickel subsulfide(Ni₃S₂), nickel oxide (NiO), or nickel sulfate hexahydrate (NiSO₄6H₂O)6 hr/day, 5 days per week for 65 days to determine the immunotoxicityof these compounds. Exposure concentrations were 0.11, 0.45,and 1.8 mg Ni/m³ for Ni₃S₂, 0.47, 2.0, and 7.9 mg Ni/m³ forNiO; and 0.027, 0.11, and 0.45 mg Ni/m³ for NiSO₄. Thymic weightswere decreased only in mice exposed to 1.8 mg Ni/m³ Ni₃S₂. Increasednumbers of lung-associated lymph nodes (LALN), but not spleennucleated cells, were seen with all compounds. Nucleated cellsin lavage samples were increased in mice exposed to the highestconcentrations of NiSO₄ and NiO and to 0.45 and 1.8 mg Ni/m³Ni₃S₂. Increased antibody-forming cells (AFC) were seen in LALNof mice exposed to 2.0 and 7.9 mg Ni/m³ NiO and 1.8 mg Ni/m³Ni₃S₂. Decreased AFC/10⁶ spleen cells were observed in miceexposed to NiO, and decreased AFC/spleen were seen for miceexposed to 1.8 mg Ni/m³ Ni₃S₂. Only mice exposed to 1.8 mg Ni/m³Ni₃S₂ had a decrease in mixed lymphocyte response. All concentrationsof NiO resulted in decreases in alveolar macrophage phagocyticactivity, as did 0.45 and 1.8 mg Ni/m³ Ni₃S₂. None of the nickelcompounds affected the phagocytic activity of peritoneal macro-phages.Only 1.8 mg Ni/m³ Ni₃S₂ caused a decrease in spleen naturalkiller cell activity. Results indicate that inhalation exposureof mice to nickel can result in varying effects on the immunesystem, depending on dose and physicochemical form of the nickelcompound. These nickel-induced changes may contribute to significantimmunodysfunction.     

Comparative Inhalation Toxicity of Nickel Subsulfide to F344/N Rats and B6C3F1 Mice Exposed for 12 Days

Comparative Inhalation Toxicity of Nickel Subsulfide to F344/NRats and B6C3F₁ Mice Exposed for 12 Days. BENSON, J. M., CARPENTER,R. L., HAHN, F. F., HALEY, P. J. HANSON, R. L., HOBBS, C. H.,PICKRELL, J. A., AND DUNNICK, J. K. (1987). Fundam Appl. Toxicol.9, 251–265. Groups of F344/N rats and B6C3F₁ mice wereexposed to aerosols of nickel subsulfide (Ni₃S₂) 6 hr/day for12 days not including weekends. Actual exposure concentrationswere 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 andmice increased linearly with exposure concentration. Two malerats and all mice exposed to 10.0 mg Ni₃S₂/m³ died before theend of the exposures. Exposure to Ni₃S₂ had no elfect on thenatural killer cell activity of mouse spleen cells. Lesionsin rats and mice related to inhalation of Ni₃S₂ were found inthe nasal epithelium, lung, and bronchial lymph nodes. The mostextensive lesions were found in the lung and included necrotizingpneumonia. Emphysema developed in rats exposed to 5.0 or 10.0mg Ni₃S₂/m³ while fibrosis developed in mice exposed to 5.0mg Ni₃S₂/m³ Degeneration of the respiratory epithelium and atrophyof the olfactory epithelium of the nose occurred in rats exposedto as low as 0.6 mg Ni₃S₂/m³ and mice exposed to 1.2 mg/m³ Resultsindicate 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 roastingfume and dust and 0.1 mg/m³ as Ni for soluble compounds) canproduce lesions in the respiratory tract. Atrophy of lymphoidtissues (spleen, thymus, and bronchial lymph nodes) was foundin animals of the highest exposure concentration. Degenerationof the testicular germinal epithelium was also observed in miceand rats that survived 5.0 or 10.0 mg/m³ exposure concentrations.     

Lung Toxicity after 13-Week Inhalation Exposure to Nickel Oxide, Nickel Subsulfide, or Nickel Sulfate Hexahydrate in F344/N Rats and B6C3F1 Mice

Lung Toxicity after 13-Week Inhalation Exposure to Nickel Oxide,Nickel Subsulfide, or Nickel Sulfate Hexahydrate in F344/N Ratsand B6C3F₁ Mice. DUNNICK, J. K., ELWELL, M. BENSON, J. M., HOBBS,C. H., HAHN, F. F., HALY, P. J., CHENG, Y. S., AND EIDSON, A.F. (1989). Fundam. Appl. Toxicol. 12, 584–594. The relativetoxicity of nickel oxide (NiO), nickel sulfate hexahydrate (NiSO₄6H₂O)and nickel subsulfide (Ni₃S₂) was studied in F344/N rats andB6C3F₁ mice after inhalation exposure for 6 hr/day, 5 days/week,for 13 weeks. Exposure concentrations used (as mg Ni/m³ were0.4–7.9 for NiO, 0.02–0.4 for NiSO₄ 6H₂O and 0.11–1.8for Ni₃S₂. No exposure-related effects on mortality and onlyminor effects on body weight gain were seen in rats or mice.The most sensitive parameter for nickel toxicity was histopathologic change in the lungs of exposed animals where chronic activeinflammation, fibrosis, and alveolar macrophage hyperplasiawerez associated with nickel exposure. There was an exposure-related increase in lung weight in rats and mice. Equilibriumlevels of nickel in the lung were reached by 13 weeks of nickelsulfate and nickel subsulfide exposure, whereas lung levelsof nickel continued to increase throughout exposure to nickeloxide. Additional exposure-related histopathologic lesions intreated animals included atrophy of the olfactory epitheliumafter nickel sulfate and nickel subsulfide exposure. No nasallesions were seen after nickel oxide expo sure. Lymphoid hyperplasiaof the bronchial lymph nodes developed in animals exposed toall three nickel compounds. The order oftoxicity correspondedto the water solubility of the nickel compounds, with nickelsulfate being most toxic, followed by nickel subsulfide andnickel oxide.     

Comparative Acute Toxicity of Four Nickel Compounds to F344 Rat Lung

Comparative Acute Toxicity of Four Nickel Compounds to F344Rat Lung. BENSON, J. M, HENDERSON, R.F., MCCLELLAN, R.O., HANSON,R.L., AND REBAR, A.H. (1986). Fundam. Appl. Toxicol. 7, 340-347.Nickel subsulfide (Ni₃S₂), nickel chloride (NiCl₂), nickel sulfate(NiSO₄), and nickel oxide (NiO) are compounds of widely differingsolubility encountered in the nickel-refining and electroplatingindustries. Inhalation is a common route of exposure and toxicityto the respiratory tract is possible. The purpose of this studywas to evaluate the biochemical, cytological, and morphologicalchanges in lung following administration of these compoundsby intratracheal instillation. F344/Crl rats were administereda single dose of nickel compound containing 0.0, 0.01, 0.10,or 1.0 µmol Ni by intratracheal instillation. Rats weresacrificed at 1 or 7 days after compound administration, withhalf the animals in each exposure group taken for determinationof nickel lung burden and the remaining half used for evaluationof biochemical, cytological, and histological changes. In thelatter group, the right lung was lavaged and the fluid obtainedwas analyzed for indicators of pulmonary inflammation: lactatedehydrogenase (LDH), ß-glucuronidase (BG), total protein(TP), glutathione reductase (GR), glutathione peroxidase (GP),and sialic acid (SA). Total and differential cell counts oncells recovered in lavage fluid were also determined. The leftlobe was examined for morphological changes. Clearance of nickelfrom the lung was most rapid for NiCl₂ and NiSO₄, followed byNi₃S₂ and NiO. Minimal changes in all parameters were observedat 1 day after exposure. No significant changes in any parameteroccurred in rats exposed to NiO, while Ni₃S₂, NiSO₄, and NiCl₂caused increases in LDH, BG, TP, GR, SA, and total nucleatedcells at 7 days. Alveolitis was also observed histologicallyin Ni₃S₂-, NiSO₄-, and NiCl₂-exposed animals at 7 days. Resultsindicated the following toxicity ranking for the four compounds:Ni₃S₂ {small tilde} NiSO4 {small tilde} NiCl2 >> NiO.Toxicity appears to be related to the solubility of these compounds.     

Inhalation Fertility and Reproduction Studies with O,O'- Dimethylphosphorodithioate in Sprague-Dawley Rats

Inhalation Fertility and Reproduction Studies with O,O'-Dimethylphosphorodithioatein Sprague-Dawley Rats. HEYDENS, W. F., AND KRONENBERG, J. M.(1989). Fundam. Appl Toxicol. 12, 62–69. Groups of 15male and 35 female Sprague-Dawley rats were exposed to 0,0'-dimethylphosphorodithioate(DMPDT) 6 hr/day, 5 days/week for 11 weeks. Initial target concentrationswere 0, 4, 25, and 200 mg/m³ However, because of excessive toxicity,the high exposure level was reduced to 125 mg/m³ after 8 weeks.Exposed males were cohoused with two unexposed females immediatelyfollowing the exposure period and later mated to an additionaltwo unexposed females following a 16-week recovery period. Exposedfemales were cohoused with untreated males, and exposures wereresumed after mating and continued during gestation. Some femaleswere terminated at midgestation to assess fertility, while otherswere allowed to deliver their pups. F₁ animals were terminatedfor histological examination or mated to assess fertility. High-exposurelevel F₀ males were infertile after exposures, and there waslittle or no recovery. The fertility of low-exposure level maleswas not affected, but equivocal results were obtained at themid-exposure level. In this study, testicular lesions were observedonly in high level F₀ males. However, testicular lesions werealso noted in a few males exposed to 4 and 25 mg/³ in a concurrentsubchronic toxicity study. Female fertility was apparently unaffectedby exposure, and no treatment-related effects were noted inmales or females exposed in utero     

Thirteen-Week, Repeated Inhalation Exposure of F344/N Rats and B6C3F1 Mice to Ferrocene

Ferrocene (dicyclopentadienyl iron; CAS No. 102-54-5) is a relativelyvolatile compound used as a chemical intermediate, a catalyst,and an antiknock additive in gasoline. This organometallic chemicalis of particular interest because of its structural similaritiesto other metallocenes, some of which are carcinogenic. F344/Nrats and B6C3F₁ mice were exposed to 0, 3.0, 10, and 30 mg ferrocenevapor/m³, 6 hr/day, 5 days/week, for 13 weeks. During theseexposures, no rats or mice died, nor were any clinical signsof ferrocene-related toxicity observed. At the end of the exposures,male rats exposed to the lowest and highest level of ferrocenehad decreased body weight gains compared to filtered-air-exposedcontrol male rats, while body weight gains for all groups ofboth ferrocene- and filtered-air-exposed female rats were similar.Male mice exposed to ferrocene had no differences in body weightgains, compared to controls, but female mice had decreases inbody weight gains at the 10 and 30 mg/m³ exposure levels. Therewere exposure concentration- and exposure-time-related increasesin lung burdens of iron. The mean iron lung burden in rats exposedto 30 mg ferrocene vapor/m³ for 90 days was four times greaterthan the burden in control rats. No exposure-related changesin respiratory function, lung biochemistry, bronchoalveolarlavage cytology, total lung collagen, clinical chemistry, andhematology parameters were observed. This suggests that theaccumulations of iron in lung did not cause an inflammatoryresponse nor any functional impairment of the lung. There wereno indications of developing pulmonary fibrosis nor of any hematologictoxicity. No exposure-related gross lesions were seen in anyof the rats or mice at necropsy. Exposure-related histopathologicalterations, primarily pigment accumulations, were observedin the nose, larynx, trachea, lung, and liver of both species,and in the kidneys of mice. Lesions were most severe in thenasal olfactory epithelium where pigment accumulation, necrotizinginflammation, metaplasia, and epithelial regeneration occurred.Nasal lesions were observed in all ferrocene-exposed animalsand differed only in severity, which was dependent on the exposureconcentration. Histochernical stains of these target tissuesshowed the presence of iron ions. The results suggest that themechanism of ferrocene toxicity may be the intracellular releaseof ferrous ion through ferrocene metabolism, followed by eitheriron-catalyzed lipid peroxidation of cellular membranes or theiron-catalyzed Fenton reaction to form hydroxyl radicals thatdirectly react with other key cellular components, such as proteinor DNA.     

Alterations in Particle Accumulation and Clearance in Lungs of Rats Chronically Exposed to Diesel Exhaust

Alterations in Particle Accumulation and Clearance in Lungsof Rats Chronically Exposed to Diesel Exhaust. WOLFF, R. K.,HENDERSON, R. F., SNIPES, M. B., GRIFFITH, W. C., MAUDERLY,J. L., CUDDIHY, R. G., AND MCCLELLAN, R. 0. Fundam Appl. Toxicol9, 154–166. F344 rats were chronically exposed to dieselexhaust at target soot concentrations of 0 (control, C), 0.35(low, L), 3.5 (medium, M), and 7.0 (high, H) mg/m³ Accumulatedlung burdens of diesel soot were measured after 6, 12, 18, and24 months of exposure. Parallel measurements of particle depositionand clearance were made to provide insight into the mechanismsof particle accumulation in lungs. The fractional depositionof inhaled ⁶⁷Ga₂O₃ particles after 6, 12, 18, and 24 monthsof exposure and of inhaled ¹³⁴Cs-fused aluminosilicate particlesafter 24 months were similar for all groups. Progressive increasesin lung burdens of soot particles were observed in M and H exposedrats, reaching levels of 11.5 ± 0.5 and 20.5 ±0.8 mg/lung (SE), respectively, after 24 months. Rats in theL group had smaller relative increases in lung burden, reachinglevels of 0.60 ± 0.02 mg/lung after 24 months. Trachealmucociliary clearance measurements, using ^99mTc-macroaggitatedalbumin deposited in the trachea, showed no changes at anytime.There were statistically significant increases inclearance half-timesof inhaled radiolabeled particles of ⁶⁷Ga₂O₃ as early as 6 monthsat the H level and 18 months at the M level; no significantchanges were seen at the L level. Rats inhaled fused aluminosilicateparticles labeled with ¹³⁴Cs after 24 months of diesel exhaustexposure to measure long-term components of pulmonary clearance.The long-term clearance half-times were 79 ± 5, 81 ±5, 264 ± 50, and 240 ± 50 days (± SE) forthe C, L, M, and H groups, respectively. Differences were significantbetween the C and both the M and H exposure groups (p <0.01).Lung burdens of diesel soot were more than expected at the Hand M levels and were also associated with impaired particleclearance while smaller responses were observed in both burdensand clearance at the L level.     

The Chronic Toxicity and Oncogenicity of Inhaled Technical-Grade 1,3-Dichloropropene in Rats and Mice

The Chronic Toxicity and Oncogenicity of Inhaled Technical-Grade1,3-Dichloropropene in Rats and Mice. LOMAX, L, G., STOTT, W.T., JOHNSON, K. A., CALHOUN, L. L., YANO, B. L., AND QUAST,J. F. (1989). Fundam. Appl. Toxicol. 12, 418–431. Maleand female Fischer 344 rats and B6C3F1 mice were exposed byinhalation to target concentrations of 0, 5, 20, or 60 ppm (0,22.7, 90.8, or 272 mg/m³) technical-grade 1,3-dichloropropene(DCPT) 6 hr/day, 5 days/week, for upto 2 years. Ancillary groupsof rats and mice were exposed for 6- and 12- month periods.Significant treatment-related nonneoplastic changes followingexposure for 2 years were morphological alterations in the nasaltissues of rats exposed to 60 ppm and mice exposed to 20 or60 ppm DCPT. In addition, mice exposed to 20 or 60 ppm had hyperplasiaof the transitional epithelium lining the urinary bladder. Survivalof male and female rats and mice exposed to DCPT was similarto that of the corresponding controls. No statistically increasedtumor incidence was observed in treated rats. The only neoplasticresponse observed in mice was an increased incidence of benignlung tumors (bronchioloalveolar adenomas) in male mice exposedto 60 ppm DCPT (22/50 versus 9/50 in controls).     

Acute Inhalation Toxicopathology of Lithium Combustion Aerosols in Rats

Acute Inhalation Toxicopathology of Lithium Combustion Aerosolsin Rats. Rebar, A. H., Greenspan, B. J., and Allen, M. D. (1986).Fundam. Appl. Toxtcol. 7, 58-67. Male and female F344/Lov ratswere exposed to aerosols produced by burning lithium metal underconditions, designed to stimulate a fire in the containmentbuilding of a fusion reactor. Lithium combustion aerosols weregenerated by sweeping lithium vapor into air atmospheres withcontrolled CO₂ and H₂O concentrations. Chemical analyses ofthe aerosols produced indicated a dependence of the chemicalform of carbon dioxide concentrations and relative humidity.Under conditions of low CO₂ concentration and low relative humidity(<25%), the aerosol was predominantly lithium monoxide withsome lithium hydroxide and about 12% lithium carbonate. Underconditions of high relative humidity (>75%), the aerosolwas primarily lithium hydroxide with about 23% A lithium carbonate.Although these two aerosols might be expected to have differentacute toxicities based on their differing alkalinities, the14-day LC50 values (with 95% confidence limits) determined after4-hr exposures were 940 (730-1200) mg/m³ for the lithium oxideand hydroxide mixture and 960 (830-1200) mg/m³ for the lithiumhydroxide aerosols. Histopathologic lesions were observed inthe nasal turbinates, larynx, and occasionally in the lungswith both aerosols. The most prominent lesions were necrotizinglaryngitis and ulcerative rhinitis. Pulmonary lesions representeda secondary extension of the upper respiratory tract lesionsrather than a primary manifestation of lithium toxicity. Thesimilarities in the LC50 valus and also in the histopathologiclesions observed suggest that any Li2O in the aerosol reactedrapidly with water vapor in the respiratory tract to form LiOHprior to deposition.     

Four-Week Inhalation Toxicity Study with Ludox Colloidal Silica in Rats: Pulmonary Cellular Responses

Four-Week Inhalation Toxicity Study with Ludox Colloidal Silicain Rats: Pulmonary Cellular Responses. WARHEIT, D. B., CARAKOSTAS,M. C, KELLY, D. P., AND HARTSKY, M. A. (1991). Fundam. Appl.Toxicol. 16, 590–601. This study was designed to complementa traditional subchronic inhalation toxicity study with Ludoxcolloidal silica. CD rats were exposed nose-only for 2 or 4weeks at concentrations of 0, 10, 50, and 150 mg/m³ Ludox (driedSiO₂). Additional groups of rats exposed for 4 weeks were givena 3-month recovery period. Following exposure and/or recovery,fluids and cells were recovered from the lungs by bronchoalveolarlavage (BAL) and measured for cellular and biochemical parameters.Additional groups of animals were processed for cell labelingstudies or lung deposition studies. Inhaled doses of Ludox colloidalsilica were measured after 4-week exposures and were found tobe 489 µg/lung (10 mg/m³ group), 2418 µg/lung (50mg/m³), and 7378 µg/lung (150 mg/m³), respectively. Resultsshowed that exposures to 150 mg/m³ Ludox for 2 or 4 weeks producedpulmonary inflammation along with increases in BAL protein,LDH, and alkaline phosphatase values (p<0.05) and reducedmacrophage phagocytosis. Inflammatory responses, evidenced byincreased numbers of neutrophils, were also measured in thelungs of the 50 mg/m³ group following 2 and/or 4 weeks of exposure.Most biochemical parameters for all groups returned to controlvalues following a 3-month recovery period. Autoradiographicstudies demonstrated that the labeling indices of terminal bronchiolarand lung parenchymal cells were generally increased in the 50and 150 mg/m³ groups after 2 and 4 weeks of exposure but, withone exception, returned to normal levels following a 3-monthpostexposure period. No significant alterations in any measuredparameters were detected in rats exposed to 10 mg/m³ Ludox atany time postexposure. The determination of a no-observable-effectlevel (NOEL) of 10 mg/m³ was consistent with results obtainedby conventional toxicology methods and affirms the utility ofthese biochemical, cellular, and autoradiographic techniquesfor providing a predictive screen to assess the toxicity ofinhaled particles.     

Peracute Toxic Effects of Inhaled Hydrogen Sulfide and Injected Sodium Hydrosulfide on the Lungs of Rats

Peracute Toxic Effects of Inhaled Hydrogen Sulfide and InjectedSodium Hydrosulfide on the Lungs of Rats. LOPEZ, A., PRIOR,M. G., REIFFENSEIN, R. J., AND GOODWIN, L. R. (1989). FundamAppl Toxicol. 12, 367–373. This study was designed totest whether intraperitoneally injected sodium hydrosulfide(NaHS) would mimic the pulmonary alterations induced by lethalperacute exposure to an atmosphere containing hydrogen sulfide.Groups of five Sprague- Dawley rats were exposed to an atmosphereof either 2317.6 ± 547.3 mg m^-3 H₂S (H₂S group) or noH₂S (air group), or were injected intraperitoneally with a solutioncontaining 30 mg kg^-1 sodium hydrosulfide (NaHS group) or salinesolution (vehicle control). Rats of the air and saline groupswere killed by cervical dislocation. All rats exposed to H²Sor injected with NaHS died within 3 min; however, only ratsexposed to H²S showed severe respiratory distress in the agonicphase preceding death. In addition, rats in the H²S group hada notable discharge of serous fluid from the mouth and nostrils.At necropsy, all rats in the H²S group had gross and histologicevidence of pulmonary edema characterized by massive extravasationof eosinophilic fluid into the bronchcalveolar space. In contrastthe lungs of rats injected with NaHS or saline or exposed toair were unaffected. It was concluded that the edematogeniceffect of H²S in the lungs cannot be reproduced by injectionof NaHS. The severity of lung edema induced by a peracute exposureto H² was extensive enough to account for death.     

Comparative toxicity of nickel oxide, nickel sulfate hexahydrate, and nickel subsulfide after 12 days of inhalation exposure to F344/N rats and B6C3F1 mice

The relative toxicity of nickel oxide (NiO), nickel sulfate hexahydrate. (NiSO4.6H2O), and nickel subsulfide (Ni3S2) was studied in F344/N rats and B6C3F1 mice after inhalation exposure for 6 h/day, 5 days/week for 12 exposure days. Exposure concentrations used (as mg Ni/m3) were 0.9-23.6 for NiO; 0.8-13.3 for NiSO4.6H2O, and 0.4-7.3 for Ni3S2. For each compound there were 5 exposure groups plus a control group. NiSO4.6H2O was the most toxic compound with exposure related mortality seen at exposure concentrations of 13.3 mg/m3 in rats and 1.6 mg/m3 and above in mice. For Ni3S2, mortality was seen in mice (but not in rats) at the highest exposure concentration (7.3 mg/m3). No mortality was seen after NiO exposure. Lesions of the lung and nasal cavity were seen in both rats and mice after exposure to NiSO4.6H2O and Ni3S2 at the 4 highest exposure concentrations. Lesions of the lung were seen primarily at the highest exposure concentrations after NiO exposure. The amount of nickel in the lungs at the end of exposure varied in relation to the water solubility of the compounds. Based on these 2-week studies, the toxicity ranking was NiSO4.6H2O greater than Ni3S2 much greater than NiO. Additional studies are in progress to assess the relative toxicities of these three nickel compounds after 90-day exposures.     

Pulmonary Response to Toner upon Chronic Inhalation Exposure in Rats

Pulmonary Response to Toner upon Chronic Inhalation Exposurein Rats. MUHLE, H., BELLMANN, B., CREUTZENBERG, O., DASENBROCK,C., ERNST, H., KILPPER, R., MACKENZIE, J. C., MORROW, P., MOHR,U., TAKENAKA, S., AND MERMELSTEIN, R., Fundam. Appl. Toxicol.17, 280–299. A chronic inhalation study of a test tonerwas conducted by exposure of groups of F-344 rats for 6 hr/day,5 days/week for 24 months The test toner was a special Xerox9000 type xerographic toner, enriched in respirable-sized particlescompared to commercial toner, such that it was about 35% respirableaccording to the ACGlH criteria. The target test aerosol exposureconcentrations were 0, 1.0 (low), 4.0 (medium), and 16.0 (high)mg/m³. Titamum dioxide (5 mg/m³) and crystalline silicon dioxide(1 mg/m³), used as negative and pasitive controls for fibrogenicity,were also evaluated. Inhalation of the test toner or the controlmaterials showed no signs of overt toxicity. Body weight, clinicalchemistry values, food consumption, and organ weights were normalin the toner- and TiO₂-exposed groups, except for a 40% increasein lung weight in the toner highexposure group. All of the changesin the toner-exposed groups were restricted to the lungs orassociated lymph nodes. A chronic inflammatory response wasevident from the bronchoalveolar lavage parameters for the tonerhigh-exposure group. The incidence of primary lung tumors wascomparable among the three toner-exposed groups and the TiO²-exposed,and air-only controls, as well as consistent with historicalbackground levels A mild to moderate degree of lung fibrosiswas observed in 92% of the rats in the toner high-exposure group,and a minimal to mild degree of fibrosis was noted in 22% ofthe animals in the toner high-exposure group. The pulmonarychanges in the toner high-exposure group were smaller in magnitudethan those found in the crystalline silica-exposed group. Thecomparative fibrogenic potency of TiO², toner, and SiO² wasestimated to be 1:5:418 using a dasimetric model and assuminga common mechanistic basis. There were no pulmonary changesof any type at the toncr low-exposure level, which is most relevantin regard to potential human exposures The lung alterationsin the toner high-exposure group are interpreted in terms of"lung overloading," a generic response of the respiratory systemto saturation of its detoxification capacity. The maximum tolerateddose (MTD) criterion was met at the toner high (16 mg/m³)-exposurelevel.     

Effects of Inhaled Chromium Dioxide Dust on Rats Exposed for Two Years

Effects of Inhaled Chromium Dioxide Dust on Rats Exposed forTwo Years. LEE, K. P., ULRICH, C. E., GEIL, R. G., AND TROCHIMOWICZ,H. J. (1988). Fundam. Appl. Toxicol 10, 125–145. Ratswere exposed by inhalation to chromium dioxide (C1O2) dust atdesign concentrations of 0, 0.5 mg/m³(stabilized and unstabilized,respectively), or 25 mg/m³ (stabilized) for 6 hr/day, 5 days/weekfor 2 years. No dust-exposure-related pathological changes otherthan lung lesions were observed in all exposed rats. There wereno significant differences in pulmonary responses between unstabilizedand stabilized CrC>2 at the 0.5 mg/m³ exposure level. Thelungs showed minute dust deposition in the alveoli adjacentto the alveolar ducts, but maintained an intact general architecture.The pulmonary responses satisfied the biological criteria fora nuisance dust. At 25 mg/m³, dust deposition was sharply confinedto the alveoli in the alveolar duct region. Alveolar walls enclosingdust-laden macrophage (dust cell) aggregates were thickenedwith hyperplastic Type II pneumocytes and slightly collagenizedfibrosis. Alveoli adjacent to the terminal bronchioles werelined with bronchiolar epithelium (alveolar bronchiolar-ization).In addition, lungs showed foamy macrophage response, cholesterolgranulomas, alveolar protoeinosis, and minute fibrotic pleurisy.These pulmonary lesions occurred predominantly in female rats.Of 108 female rats, 6 developed keratin cysts and 2 had cystickeratinizing squa-mous cell carcinoma (CKSCC). None of 106 malerats had either a keratin cyst or a CKSCC. The lung tumors developedfrom metaplastic squamous cells in the areas of alveolar bronchio-larizationat the alveolar duct region. The lung tumors were well differentiatedand devoid of characteristics of true malignancy. The CKSCCis an experimentally induced, unique tumor type and is differentfrom the type of spontaneous lung tumor seen in man or animals.The relevance to man of this type of lung tumor appears to benegligible.     

Inhalation Toxicity Studies of Cobalt Sulfate in F344/N Rats and B6C3F1 Mice

Inhalation Toxicity Studies of Cobalt Sulfate in F344/N Ratsand B6C3F1 Mice. BUCHER, J. R., ELWELL, M. R., THOMPSON, M.B., CHOU, B. J., RENNE, R., AND RAGAN, H. A. (1990). Fundam.Appl. Toxicol. 15, 357–372. Groups of 10 F344/N rats andB6C3F1 mice of each sex were exposed to cobalt sulfate heptahydrateaerosols of 0, 0.3, 1.0, 3.0, 10, or 30 mg/m3, 6 hr per day,5 days per week, for 13 weeks. All rats and female mice andall but 2/10 male mice exposed at the top concentration survivedto the end of the studies. Polycythemia was observed in exposedrats but not in mice. Sperm motility was decreased in mice exposedat 3 mg/m3 (the lowest concentration evaluated) and at higherconcentrations, and increased numbers of abnormal sperm anddecreased testis and epididymal weights occurred in mice exposedto 30 mg/m3. Cobalt content in the urine of rats increased withincreasing atmospheric cobalt exposure. Primary histopathologiceffects were limited to the respiratory tract. Lesions in ratsand mice included degeneration of the olfactory epithelium,squamous metaplasia of the respiratory epithelium, and inflammationin the nose; inflammation, necrosis, squamous metaplasia, ulcers(rats), and inflammatory polyps (rats) of the larynx; metaplasiaof the trachea (mice); and fibro-sis, histiocytic infiltrates,bronchiolar epithelial regeneration, and epithelial hyperplasiain the alveoli of the lung. The most sensitive tissue was thelarynx, with squamous metaplasia observed in rats and mice atthe lowest exposure concentration of 0.3 mg/m3. Thus, a no-observed-adverse-effectlevel was not reached in these studies     

Subchronic and Chronic Inhalation Toxicity of Antimony Trioxide in the Rat

Fischer 344 rats were exposed by inhalation to Sb₂O₃ (antimonytrioxide) dust at exposure levels of 0, 0.25, 1.08, 4.92, and23.46 mg/m³ for 6 hr/day, 5 days/week for 13 weeks followedby a 27-week observation period. Subsequently, an inhalationon-cogenicity study was conducted at exposure levels of 0, 0.06,0.51, and 4.50 mg/m³ for 12 months followed by a 12-month observationperiod. The Sb₂O₃ in the subchronic study had a mass medianaerodynamic diameter (MMAD) of 3.05 ± 0.21 microns (mean± SD) with a geometric standard deviation (GSD) of 1.57± 0.06. In the chronic study, the MMAD was 3.76 ±0.84 and the GSD was 1.79 ± 0.32. Except for the eyes,no adverse clinical observations were attributed to Sb₂O₃ ineither study. In the subchronic study, corneal irregularitieswere seen after about 2 weeks of exposure and did not abateduring the observation period. In the chronic study, ophthalmoscopicevaluation at 24 months revealed a dose-related increase incataracts of 11, 24, 28, and 32% (both sexes combined) for eachgroup, respectively. Body weights were significantly lower (6%)than the control group's weights in the 23.46 mg/m³ males inthe subchronic study. These rats did not recover this weightduring the 27-week observation period. Body weights of the femalesin both studies and males in the chronic study were unaffected.There were no Sb₂O₃ effects on clinical chemistry or he-matologyin either study. Mean absolute and relative lung weights weresignificantly increased in the 4.92 and 23.46 mg/m³ groups inthe subchronic study. The 23.46 mg/m³ group's lung weights didnot recover to control levels during the 27-week observationperiod. Lung weights for rats in the chronic study were unaffected.Microscopic changes in the lungs in the subchronic and chronicstudy were limited to subacute-chronic interstitial inflammation,increased numbers of alveolar-in-traalveolar macrophages, foreignmaterial in the alveolar-in-traalveolar macrophages in the peribronchialand perivascular (chronic study only) lymphoid aggregates andin the peribronchial lymph nodes, granulomatous inflammation/granulomas,and fibrosis. In the chronic study, any observed neoplasms occurredwith comparable incidence among all groups and were within thehistorical range for controls. Clearance of Sb₂O₃ from the lungwas burden dependent and was reduced by 80/ in the 4.50 mg/m³group in the chronic study. The previously reported studies,which found Sb₂O₃ to be a carcinogen, were run at higher lungburdens. Under the exposure conditions of the current study,Sb₂O₃ was not a carcinogen.     

Subchronic Inhalation Exposure of Dearomatized White Spirit and C10-C11 Isoparaffinic Hydrocarbon in Sprague-Dawley Rats

Subchronic Inhalation Exposure of Dearomatized White Spiritand C₁₀-C₁₁ Isoparaffin Hydrocarbon in Sprague-Dawley Rats.PHILLIPS, R. D., AND EGAN, G. F. (1984). Fundam. Appl. Toxicol.4, 808–818. Groups of 35 male and 35 female Sprague-Dawleyrats were exposed to either Dearomatized White Spirit (DAWS)vapor at concentrations of 1.97 and 5.61 g/m³ or C₁₀-C₁₁ IsoparaffinicHydrocarbon (IPH) vapor at concentrations of 1.91 and 5.62 g/m³.These concentrations were targeted for the recommended occupationalexposure limits and three times that value, respectively. Exposureswere 6 hr-day, 5 days/week for 12 weeks. Following Weeks 4,8. and 12 of exposure, a total of 10, 10, and 15 rats, respectively,from each group were sacrificed. Clinical chemistry and hematologyparameters were measured in blood samples taken immediatelyprior to sacrifice, and selected organs were removed and weighed.Twenty-three organs and tissues from each animal were examinedmicroscopically. There were no deaths during the course of thisstudy related to either DAWS or IPH. Mean body weights weresignificantly tower than controls in male rats following exposureto 5.61 g/m³ DAWS, and 5.62 or 1.91 g/m³ IPH. Body weights werenot affected in females. The primary effects from DAWS or IPHexposure were observed in the kidneys of male rats only fromboth exposure groups beginning at Week 4. Evidence of mild tubulartoxicity, such as regenerative tubular ephhelia and dilatedtubules containing proteinaceous casts, was observed at thecortieomedullary junction. The incidence and severity appearedto increase with increasing concentration and exposure duration.There were scattered instances of statistically significantincreases in liver and kidney weights in both males and females.With the exception of the mild male rat tubular nephrotoxiriry,other significant toxic effects were not observed at levelstested     

Two-Week, Repeated Inhalation Exposure of F344/N Rats and B6C3F Mice to Ferrocene

Two-Week, Repeated Inhalation Exposure of F344/N Rats and B6C3F¹Mice to Ferrocene. SUN, J. D., DAHL, A. R., GILLETT, N. A.,BARR, E. B., CREWS, M. L., EIDSON, A. F., BECHTOLD, W. E., BURT,D. G., DIETER, M. P., AND HOBBS, C. H. (1991). Fundam. ApplToxicol. 17, 150-158. Ferrocene (dicyclopentadienyl iron; CASNo. 102-54-5) is a relatively volatile, organometallic compoundused as a chemical intermediate, a catalyst, and as an antiknockadditive in gasoline. It is of particular interest because ofits structural similarities to other metallocenes that havebeen shown to be carcinogenic. F344/N rats and B6C3F, mice wereexposed to 0, 2.5, 5.0, 10, 20, and 40 mg ferrocene vapor/m3,6 hr/day for 2 weeks. During these exposures, there were nomortality and no observable clinical signs of ferrocene-relatedtoxicity in any of the animals. At the end of the exposures,male rats exposed to the highest level of ferrocene had decreasedbody-weight gains relative to the weight gained by filteredair-exposed control rats, while body-weight gains for all groupsof both ferrocene- and filtered air-exposed female rats weresimilar. Male mice exposed to the highest level of ferrocenealso had decreased body-weight gains, relative to controls,while female mice had relative decreases in body-weight gainsat the three highest exposure levels. Male rats had a slightdecrease in relative liver weight at the highest level of exposure,whereas no relative differences in organ weights were seen infemale rats. Male mice had exposure-relative decreases in liverand spleen weights, and an increase in thymus weights, relativeto controls. For female mice, relative decreases in organ weightswere seen for brain, liver, and spleen. No exposure-relatedgross lesions were seen in any of the rats or mice at necropsy.Histopathological examination was done only on the nasal turbinates,lungs, liver, and spleen. The only exposure-related findingwas histopathologic lesions in the nasal turbinates of bothspecies. These lesions were primarily centered in the olfactoryepithelium and were morphologically diagnosed as subacute, necrotizinginflammation. Nasal lesions were observed in all ferrocene-exposedanimals and differed only in severity, which was dependent onthe exposure concentration. In vitro metabolism studies of ferroceneshowed that nasal tissue, particularly the olfactory epithelium,had 10 times higher "ferrocene hydroxylating" activity thandid liver tissue from the same animals. These results suggestthat the mechanism of ferrocene toxicity may be the intracellularrelease of ferrous ion through ferrocene metabolism, followedby iron-catalyzed lipid peroxidalion of cellular membranes.