Fourteen-Day Inhalation Study in Rats, Using Aged and Diluted Sidestream Smoke from a Reference Cigarette: II. DNA Adducts and Alveolar Macrophage Cytogenetics

The chemical constituents of cigarette smoke are greatly dilutedin environmental tobacco smoke (ETS). In the typical indoorenvironment where cigarettes are smoked, the mean value of respirablesuspended particles is approximately 0.1 mg/m³. In this study,we used aged and diluted sidestream smoke (ADSS) of 1R4F Universityof Kentucky research cigarettes as a surrogate for ETS and exposedSprague-Dawley rats nose-only to 0, 0.1, 1.0, and 10 mg wettotal particulate matter (WTPM)/m³ for 6 hr per day for 14 consecutivedays. DNA from lung, heart, larynx, and liver was tested foradduct formation after 7 and 14 days of exposure and after 14days of recovery. In addition, alveolar macrophages from animalsexposed for 7 days were examined for chromosomal aberrations.Exposure-related DNA adducts were not observed in any of theanimals at 0.1 or 1.0 mg WTPM/ m³, which represent ambient and10-fold exaggerated ETS concentrations, respectively. Slightdiagonal radioactive zones, characteristic of adducts observedin human smokers and in animals exposed to mainstream smoke,were observed, but only in lung and heart DNA of animals exposedto the highest concentration of ADSS (10 mg WTPM/m³), a 100-foldexaggeration of typical field measurements of ETS. The meanrelative adduct labeling values (±SE) were 8.7 (±0.2)adducts per 10' nucleotides for lung DNA and 5.7 (±0.7)adducts per 10' nucleotides for heart DNA after 14 days of exposure.No elevation in chromosomal aberrations was observed in alveolarmacrophages. These results indicate a no-observed-effect-level(NOEL) of 1.0 mg/m³ for DNA adduct formation in lung and heartand a NOEL of at least 10 mg/m³ for the induction of chromosomeaberrations in alveolar macrophages under the conditions ofthis study.     

Short-term exposure to aged and diluted sidestream cigarette smoke enhances ozone-induced lung injury in B6C3F1 mice.

To determine the effects of aged and diluted sidestream cigarette smoke (ADSS) as a surrogate of environmental tobacco smoke (ETS) on ozone-induced lung injury, male B6C3F1 mice were exposed to (1) filtered air (FA), (2) ADSS, (3) ozone, or (4) ADSS followed by ozone (ADSS/ozone). Exposure to ADSS at 30 mg/m3 of total suspended particulates (TSP) for 6 h/day for 3 days, followed by exposure to ozone at 0.5 ppm for 24 h was associated with a significant increase in the number of cells recovered by bronchoalveolar lavage (BAL) compared with exposure to ADSS alone or ozone alone. The proportion of neutrophils and lymphocytes, as well as total protein level in BAL, was also significantly elevated following ADSS/ozone exposure, when compared with all other groups. Within the centriacinar regions of the lungs, the percentage of proliferating cells identified by bromodeoxyuridine (BrdU) labeling was unchanged from control, following exposure to ADSS alone, but was significantly elevated following exposure to ozone (280% of control) and further augmented in a statistically significant manner in mice exposed to ADSS/ozone (402% of control). Following exposure to ozone or ADSS/ozone, the ability of alveolar macrophages (AM) to release interleukin (IL)-6 under lipopolysaccharide (LPS) stimulation was significantly decreased, while exposure to ADSS or ADSS/ozone caused a significantly increased release of tumor necrosis factor alpha from AM under LPS stimulation. We conclude that ADSS exposure enhances the sensitivity of animals to ozone-induced lung injury.     

Replicative dna synthesis in tissues of the rat exposed to aged and diluted sidestream smoke

Abstract

Male Sprague-Dawley rats were exposed to aged and diluted sidestream smoke (ADSS) from Kentucky 1R4F reference cigarettes for 6 h/day, 5 days/wk, for a 13-wk period. Exposure concentrations were 0, 0.1, 1, and 10 mg ADSS/m³. Exposures were conducted in whole-body inhalation chambers. Rats were held in nose-only exposure tubes for the 6-h exposures to minimize pelt deposition and subsequent ingestion of ADSS. Groups of 10 rats from each exposure group were killed after 5, 28, and 90 d of exposure to examine the rates of replicative DNA synthesis; 6 rats from each exposure group were kept for a 90-day recovery period after termination of exposures to examine replicative DNA synthesis rates. Three days prior to each scheduled necropsy, an osmotic pump containing 5-bromo-2′-deoxyuridine (BrdU) was implanted subcutaneously. After necropsy, tissues were processed for examination of BrdU-containing cells at several sites. Incorporation of BrdU was assessed either by counting the number of labeled cells along a length of an epithelial surface or by counting the number of labeled cells in an area of tissue. Tissues examined were from the nasal cavity, ventral larynx, and trachea, in addition to bronchial, bronchiolar, and alveolar regions of the lung. Endocardium, myocardium, epicardium, and aortic smooth muscle sites were also examined. Increased replicative DNA synthesis occurred in some sites of the respiratory tract at the 5-day timepoint at the mid or high exposure concentrations, although at 28 and 90 days, these effects had diminished in intensity or were not present, indicating adaptation to the ADSS exposure. The only tissues with elevated rates of replicative DNA synthesis at 90 days were the cuboidal and respiratory epithelium at the most rostra! portion of the nasal cavity at the highest exposure concentration. Increased rates of replicative DNA synthesis were not noted in heart tissues or lung alveolar epithelium at any concentration at any time point. Examination of rats killed after the end of the 90-day recovery period indicated that the increase in replicative DNA synthesis was not sustained after termination of exposures. The no observed effect level (NOEL) for increased replicative DNA synthesis after subchronic exposure to ADSS in the rat is greater than 1 mg ADSS/m³.     

Perinatal exposure to aged and diluted sidestream cigarette smoke produces airway hyperresponsiveness in older rats

Exposing rats to aged and diluted sidestream cigarette smoke (ADSS) throughout in utero and postnatal life results in airway hyperresponsiveness and an increase in pulmonary neuroendocrine cells (PNECs) and neuroepithelial bodies (NEBs) in 7- to 10-week-old rats. Since human epidemiologic studies suggest that perinatal exposure to environmental tobacco smoke (ETS) may be detrimental to the lung function of older children, this study was designed to determine if perinatal exposure alone results in airway hyperresponsiveness and increased PNECs/NEBs later in life in rats. Pregnant Sprague-Dawley rats were exposed to filtered air (FA, n = 7) or ADSS (1 mg/m3 total suspended particulates, n = 7) for 4 to 6 h/day starting on Day 3 of gestation. Their pups continued to receive the same exposure regimen postnatally until 21 days of age. Thereafter all pups were exposed to FA until about 8 weeks of age. The airway responsiveness of one female pup from each litter was then assessed using an isolated perfused lung system whereby increasing doses of methacholine (-9.25 to -7.50 log mol) were administered into the pulmonary artery and lung resistance (Rl), dynamic compliance (Cdyn), and pulmonary pressure (Ppa) were measured. The number of PNECs/NEBs and mast cells per millimeter basal lamina were determined using immunocytochemical and histological staining and morphometric analysis. Statistics were performed using an unpaired Student's t test and repeated measures analysis of variance. Perinatal ADSS exposure enhanced methacholine-induced changes in Rl (p = 0.02), Cdyn (p = 0.004), and Ppa (p = 0.007). At the highest dose of methacholine, Rl in the ADSS-exposed lungs was threefold that in FA-exposed lungs. Although total PNEC number increased approximately twofold in the ADSS-exposed animals, this change was not found to be statistically significant. Mast cell number also was not different between groups. These data suggest that exposure to ADSS during the perinatal period followed by 5 weeks exposure to FA induces airway hyperresponsiveness in the absence of a significant change in PNECs, NEBs, or mast cells.     

Subchronic Inhalation Studies on Polychlorotrifluoroethylene (3.1 Oil)

Abstract

3.1 Oil, an oligomer of chlorotrifluoroethylene (CTFE), is an inert, nonflammable, saturated and hydrogen-free chlorofluorocarbon oil of interest to the Department of Defense (DOD) as a potential hydraulic fluid. To determine the potential subchronic inhalation toxicity of this CTFE oligomer, male and female F-344 rats were exposed to air only or to 0.25, 0.50, or 1.00 mg/l of CTFE oligomer in 65 6-h inhalation exposures over a 90-day period. A dose-dependent depression in body weight gains was noted in male rats only Serum alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase activities examined at the conclusion of the study indicated a treatment-related effect in the male test rats, but not the female test rats. Notable concentration-related increases (p < .07) in relative kidney and liver weights occurred in both sexes of rats at all test concentrations. The male rats showed slight to minimal hyaline droplet formation in the kidney proximal tubule epithelium. Pronounced cy-tomegaly of hepatocytes was the predominant lesion recognized.     

Urinary thromboxane, prostacyclin, cortisol, and 8-hydroxy-2'-deoxyguanosine in nonsmokers exposed and not exposed to environmental tobacco smoke.

This study tested the hypotheses that (1) increased platelet aggregation, as measured by 2,3-dinor-thromboxane B(2) (Tx-M) and 2,3-dinor-6-keto-prostaglandin F(1alpha) (PGI-M), and (2) increased oxidative stress, as measured by 8-Hydroxy-2'-deoxyguanosine (8-OHdG), would occur in ETS-exposed nonsmokers as compared with non-ETS-exposed nonsmokers. The concentrations of the stable urinary metabolites of thromboxane (Tx-M) and prostacyclin (PGI-M), cortisol and 8-OHdG were measured in a 24-h urine sample from 3 groups of subjects: 21 nonsmokers with minimal (15 min or less per day) ETS exposure (termed non-ETS-exposed), 22 nonsmokers with at least 5 h per day of ETS exposure (termed ETS-exposed), and 20 cigarette smokers who served as a positive control group. The self-reported levels of ETS exposure were verified by personal air monitors. As compared with either group of nonsmokers, cigarette smokers excreted significantly more urinary Tx-M. Non-ETS-exposed nonsmokers showed a statistically significantly higher level of urinary Tx-M over that seen in nonsmokers with considerably more ETS exposure. Urinary concentrations of PGI-M were marginally higher in the smokers and did not differ between the nonsmoker groups. Nonsmokers exposed to at least five h of ETS per day did not have significantly higher excretion of 8-OHdG than non-ETS-exposed nonsmokers. The results from this study suggest that platelet aggregation, as measured by the thromboxane metabolite Tx-M and prostacyclin metabolite PGI-M, is not associated with ETS exposure. Therefore, platelet aggregation is not a plausible or quantitatively consistent mechanism to explain the nonlinear dose-response hypothesis of cardiovascular disease and ETS exposure.     

Ninety-Day Inhalation Study in Rats, Using Aged and Diluted Sidestream Smoke from a Reference Cigarette: DNA Adducts and Alveolar Macrophage Cytogenetics

To study the genotoxic effects of subchronic exposure to environmentaltobacco smoke, Sprague-Dawley rats were exposed to 0, 0.1, 1.0,and 10 mg total particulate matter (TPM)/m³ of aged and dilutedsidestream smoke (ADSS) from 1R4F reference cigarettes 6 hrper day, 5 days a week for 13 weeks. DNA from lung, heart, larynx,bladder, and liver was tested for adduct formation by the ³²P-postlabelingassay after 28 (except bladder) and 90 days of exposure and90 days after cessation of exposure. In addition, alveolar macrophagesfrom animals exposed for 28 or 90 days were examined for chromosomalaberrations. Exposure-related DNA adducts were not observedin any tissue in any of the animals exposed to 0.1 or 1.0 mgTPM/m³. However, increased levels of DNA adducts with diagonalradioactive zones were observed in lung, heart, and larynx DNAof animals exposed to the highest concentration of ADSS (10mg TPM/m³). Adduct analyses with varying amounts of DNA fromlungs of mid-and high-exposure animals clearly indicate thatthe dose-response for DNA adduct formation is nonlinear. Theadduct levels were highest after 90 days of exposure and weresignificantly reduced in all target tissues 90 days after cessationof exposure. Chromosomal aberrations in alveolar macrophageswere not elevated in any group after 28 or 90 days of exposure.These results indicate a no-observed-effect-level (NOEL) ofat least 1.0 mg/m³ for DNA adduct formation in lung, heart,and larynx, and a NOEL of at least 10 mg/m³ for the inductionof chromosome aberrations in alveolar macrophages, under theconditions of this study.     

Isopropanol 13-Week Vapor Inhalation Study in Rats and Mice with Neurotoxicity Evaluation in Rats

This study was conducted to evaluate the possible subchronictoxicity as well as neurobehavioral effects of isopropanol,a widely used industrial and commercial solvent. Five groups,each containing 10 Fischer 344 rats/sex and 10 CD-I mice/sex,were exposed for 6 hr/day, 5 days/week, for 13 weeks to isopropanolvapor at concentrations of 0 (control), 100, 500, 1500, or 5000ppm. An additional 15 rats/sex were assigned to the 0, 500,1500, and 5000 ppm groups for assessment of neurobehavioralfunction. No exposure-related mortalities occurred during thestudy. The narcotic effects of isopropanol were noted only duringexposures at 1500 and 5000 ppm. These signs, noted during exposures,were typically absent following exposures. The only clinicalsigns observed following exposures included swollen perioculartissue, perinasal encrustation, and ataxia for rats of the 5000ppm group. Neurobehavioral evaluations indicated no changesin any of the parameters of the functional observational battery;however, increased motor activity for female rats in the 5000ppm group was noted at Weeks 9 and 13. Decreases in body weightand body weight gain were observed for rats of the 5000 ppmgroup at the end of the first week of exposure. During the remainingweeks, increases in body weight and/or body weight gain wereobserved for rats of the 1500 and 5000 ppm groups. No exposure-relatedeffects on body weight were noted for male mice; however, increasedbody weight and body weight gain were observed for female miceof the 5000 ppm group. Increases or decreases in food and waterconsumption generally corresponded to changes in body weightand body weight gain. Various changes in clinical pathologyparameters were observed for rats and female mice of the 5000ppm group. The only organ weight effect noted was an increasedrelative liver weight in both sexes of rats of and female miceof the 5000 ppm group. At necropsy, three were no gross lesionsdetermined to be exposure related. Furthermore, the only microscopicchange observed was hyaline droplets within the kidneys of allmale rats (including controls). The size and frequency of thehyaline droplets were increased for the isopropanol exposuregroups compared to the control group. These differences werenot clearly concentration related, although this microscopicchange was most pronouced in the high-concentration group. Neuropatholo0gicexamination revealed no exposure-related lesions in the centralor peripheral nervous system of exposed rats. Thus, repeatedexposures to isopropanol for 13 weeks produced toxic effctsonly at the highest concentration and a kidney change in malerats of unknown biological significance.     

Subchronic Inhalation Toxicity of Tetramethoxysilane in Rats

Sprague-Dawley rats were exposed 6 hr/day, 5 days a week, for28 days to tetramethoxysilane (TMOS) at concentrations of 0,1, 5, and 10 ppm (Phase I study) and to 0, 15, 30, and 45 ppm(Phase II study). All of the rats exposed to 45 ppm TMOS diedor were sacrificed in a moribund state during the 28-day studyperiod. Statistically significant changes were observed in foodconsumption, body weights, and clinical chemistry parametersin the animals exposed to 30 ppm TMOS. Males exposed to 15 ppmTMOS showed a significant decrease in total protein. No effectswere seen in rats exposed to 1, 5, and 10 ppm TMOS. Histopathologicallesions related to TMOS exposure were observed in the respiratorytract tissues and eyes of rats exposed to 15, 30, and 45 ppmTMOS. The principal types of lesions observed were ulceration,inflammation, and necrosis of epithelium. At 45 ppm, changesat these sites were severe and present in all animals. Changesat 30 ppm, while occurring in all rats, were much less severethan those seen at 45 ppm. At 15 ppm, the changes were minimaland occurred only in three males and five females. The dataof this study showed that TMOS has a steep dose-response curvewith no observable effects at 10 ppm, very minimal effects at15 ppm, moderate to severe effects at 30 ppm, and severe effectsand lethality at 45 ppm.     

Inhalation toxicity studies of aqueous dispersion resin

Aqueous dispersion resin (ADR) is a water-based acrylate copolymer designed to allow a range of ethanol concentrations for hair-spray formulations. A series of inhalation (whole-body) aerosol toxicity studies, including acute, 9-day, and 90-day exposures, was conducted to determine any toxicological effects for ADR. An acute study of ADR was conducted for 4 h with a 14-day observation period. The maximum ADR aerosol concentration was 1.07 (+/- 0.04) mg/L with a mass medium aerodynamic diameter (MMAD) value of 1.46 microm and a geometric mean (sigma(g)) of 1.42. No deaths or exposure-related lesions were observed. Thus, the LC50 value was greater than 1.07 mg/L. For the 9-day study, each group contained 10 animals/sex and was exposed for 2 h/day. The mean exposure concentrations (+/- standard deviation) were 244 (+/- 39.6), 543 (+/- 71.9), and 843 (+/- 186.2) mg/m(3) for the 250-, 500-, and 1000-mg/m(3) groups, respectively. The mean MMADs were 2.83, 2.90, and 4.09 microm for the 250-, 500-, and 1000-mg/m(3) groups, respectively, with sigma(g) values ranging from 3.15 to 6.22. Unkempt fur and alopecia in the males and females from the 1000-mg/m(3) group at sacrifice were the only exposure-related clinical signs observed. Increased lung weights in the 500- and 1000-mg/m(3) exposure groups were found. Histopathological effects, such as alveolar histiocytosis and interstitial pneumonitis, were also noted in these two exposure groups. For the 90-day study, 10 animals per sex were included in each group with a 6-wk recovery group of 5 female rats/group. Exposures were conducted for 2 h/day. The mean exposure concentrations were 30.4 (+/- 2.3), 102 (+/- 11.6), and 308 (+/- 19. 3) mg/m(3) with mean MMADs of 3.09, 2.64, and 2.67 microm and sigma(g) values ranging from 3.54 to 3.90 for exposure concentrations of 30, 100, and 300 mg/m(3), respectively. The only findings at the 90-day sacrifice were increased lung weights for the males and females in the 300-mg/m(3) group and males in the 100-mg/m(3) group. For the 6-wk recovery sacrifice of the females, the lung weights for the 300- and 100-mg/m(3) groups were increased. Histopathological effects at the 90-day sacrifice included alveolar histiocytosis and lymphadenitis in the mediastinal lymph nodes in the 100- and 300-mg/m(3) exposure groups for males and females, while alveolar histiocytosis, intraalveolar cellular debris, lymphadenitis in the mediastinal lymph nodes, and/or interstitial pneumonitis were noted in these 2 exposure groups of the females after the 6-wk recovery period. Animals exposed for 90 days to 100 and 300 mg/m(3) for 2 h had increased lung weights. However, no effects were observed in the 30-mg/m(3) exposure group. Thus, under the conditions of the present 90-day study, a no-observable-effect level (NOEL) was found to be 30 mg/m(3).     

Quantitative Histology and Cytochrome P-450 Immunocytochemistry of the Lung Parenchyma Following 6 Months of Exposure of Strain A/J Mice to Cigarette Sidestream Smoke

Abstract

Male strain A/J mice were exposed for 6 h/day, 5 days/wk to aged and diluted cigarette sidestream smoke (ADSS) at a chamber concentration of 4 mg/m³ of total suspended particulate matter (TSP). After 6 mo, the lungs were examined for altered expression of cytochrome P-450 isozymes and for differences in total alveolar tissue volume or surface area, as well as changes in the numbers of epithelial type II cells and alveolar macrophages. Morphologic measurements showed no statistically significant differences for the air, alveolar tissue, or capillary volumes of the lungs or changes in the total number of epithelial type II cells or alveolar macrophages. In contrast, cytochrome P-4501A1 was elevated in the lungs of ADSS-exposed animals and localized in capillary endothelial cells. CYP2B1 was present in airway epithelial cells as well as in epithelial cells throughout the lung parenchyma, but its distribution was not changed by ADSS exposure. Isozyme CYP2E1 was also found in airway epithelial cells, but not in the lung parenchyma, with no differences noted between ADSS exposed animals and controls. CYP2F2 was found in the bronchiolar Clara cells and in type II cells located within the alveolar parenchyma, but was also unchanged. It is concluded that chronic exposure to cigarette ADSS at 4 mg/m³ of TSP produces no changes in alveolar macrophages or epithelial type II cells in mouse lung but increases the expression of cytochrome P4501A1.     

Chronic Inhalation Study of Size-Separated Rock and Slag Wool Insulation Fibers in Fischer 344/N Rats

Abstract

This study was designed to investigate the potential pathogenic effects in Fischer 344/N rats of two different types of man-made vitreous fibers (MMVF). Eight-week-old male rats were exposed in nose-only inhalation chambers, 6 hlday, 5 dayslwk, lor 24 mo to 3 concentrations (3, 16, and 30 mg/m¹) each of the two MMVFs: a basalt-based rock wool (stone wool), and a slag wool (blast furnace). Crocidolite asbestos (10 mg/m³) was used as a positive control. The experimental groups were compared to unexposed (chamber) controls. The MMVFs used in this study were size selected to be largely respirable in rats. Interim sacrifices took place at 3- and 6-mo intervals to monitor the progression of pulmonary changes. Fibers were recovered from digested lung tissue for determination of changes in fiber number and morphology. Exposure to crocidolite asbestos was terminated after 10 mo because of increased morbidity/mortality. Exposure to rock and slag wool, while producing a dose-related nonspecific inflammatory response (rock and slag) and minimal local pulmonary fibrosis (rock only), showed no evidence of carcinogenic activity in either the lung or pleura, in contrast to crocidolite asbestos, which induced neoplasms in both tissues. Since workplace airborne levels are several orders of magnitude lower than even the lowest exposure level to which the animals were exposed, these results suggest that these MMVFs do not pose a significant health risk to humans at airborne levels found in the workplace, during installation or for the in-place product.     

Inhalation toxicity of cyclododecatriene in rats.

Cyclododecatriene (CDDT, CAS No. 4904-61-4) was tested for its inhalation toxicity in rats following repeated exposures. Male rats were exposed nose-only to CDDT for 6 hr/day, 5 days/wk for a total of 9 exposures over 2 weeks. Particular attention was paid to neurotoxicologic endpoints. Concentrations of 0 (control), 5, 50, and 260 ppm were studied. The 260 ppm chamber contained both vapor and aerosol while the 5 and 50 ppm chambers were vapor only. Four groups of 10 rats each were used to measure standard clinical signs and growth, clinical pathology (including hematology, biochemistries, and urine analysis), and tissue pathology. Another 4 groups of similar size were used for neurotoxicity testing. In the standard toxicity groups, 1/2 of the rats were sacrificed 1 day following the 9th exposure; the other half underwent a 2-week recovery period prior to being sacrificed (recovery group). During the exposures rats inhaling 260 ppm had a diminished or absent response to an alerting stimulus. Irregular respiration and lethargy were observed in these rats immediately following exposure. These signs were rapidly reversible and were not seen prior to the subsequent exposure. Body weights in rats exposed to either 50 or 260 ppm were significantly lower than the corresponding controls. No compound-related clinical pathology changes were seen in any of the test groups and tissue pathology effects only occurred in the nasal tissue. In rats exposed to 260 ppm, minimal degeneration/necrosis of nasal olfactory epithelium was observed in rats examined immediately following the exposure period. This change was not seen in the recovery rats. Functional observational battery (FOB) assessments and motor activity (MA) evaluations conducted after the 4th and 9th exposures on rats from all test groups, and specific neuropathologic evaluation on perfused brain, spinal cord, and skeletal muscle from rats exposed to 260 ppm failed to demonstrate any specific neurotoxicity. Outward signs of sedation were seen at the top level tested. Under the conditions of this test, the no-observed-adverse-effect level (NOAEL) was determined to be 5 ppm based upon a reduced rate of body weight gain in the 50 ppm group. No specific neurotoxicity was detected and the histopathologic response was limited to reversible changes in the nasal epithelia in rats exposed to 260 ppm.     

Inhalation Toxicity of Cyclododecatriene in Rats

ABSTRACT

Cyclododecatriene (CDDT, CAS No. 4904-61-4) was tested for its inhalation toxicity in rats following repeated exposures. Male rats were exposed nose-only to CDDT for 6 hr/day, 5 days/wk for a total of 9 exposures over 2 weeks. Particular attention was paid to neurotoxicologic endpoints. Concentrations of 0 (control), 5, 50, and 260 ppm were studied. The 260 ppm chamber contained both vapor and aerosol while the 5 and 50 ppm chambers were vapor only. Four groups of 10 rats each were used to measure standard clinical signs and growth, clinical pathology (including hematology, biochemistries, and urine analysis), and tissue pathology. Another 4 groups of similar size were used for neurotoxicity testing. In the standard toxicity groups, 1/2 of the rats were sacrificed 1 day following the 9th exposure; the other half underwent a 2-week recovery period prior to being sacrificed (recovery group). During the exposures rats inhaling 260 ppm had a diminished or absent response to an alerting stimulus. Irregular respiration and lethargy were observed in these rats immediately following exposure. These signs were rapidly reversible and were not seen prior to the subsequent exposure. Body weights in rats exposed to either 50 or 260 ppm were significantly lower than the corresponding controls. No compound-related clinical pathology changes were seen in any of the test groups and tissue pathology effects only occurred in the nasal tissue. In rats exposed to 260 ppm, minimal degeneration/necrosis of nasal olfactory epithelium was observed in rats examined immediately following the exposure period. This change was not seen in the recovery rats. Functional observational battery (FOB) assessments and motor activity (MA) evaluations conducted after the 4th and 9th exposures on rats from all test groups, and specific neuropathologic evaluation on perfused brain, spinal cord, and skeletal muscle from rats exposed to 260 ppm failed to demonstrate any specific neurotoxicity. Outward signs of sedation were seen at the top level tested. Under the conditions of this test, the no-observed-adverse-effect level (NOAEL) was determined to be 5 ppm based upon a reduced rate of body weight gain in the 50 ppm group. No specific neurotoxicity was detected and the histopathologic response was limited to reversible changes in the nasal epithelia in rats exposed to 260 ppm.     

Ethyl Chloride: A Two-Week Inhalation Toxicity Study and Effects on Liver Non-Protein Sulfhydryl Concentrations

Ethyl Chloride: A Two-Week Inhalation Toxicity Study and Effectson Liver Non-Protein Sulfhydryl Concentrations. Landry, T.D.,Ay res, J.A., Johnson, K.A. and Wall, J.M. (1982). Fundam. Appl.Toxicol. 2:230-234. Male and female Fischer 344 rats (6/sex/exposureconcentration)and male beagle dogs (2/exposure concentration)exposed to 0, 1600,4000 or 10 000 ppm ethyl chloride (EtCI)for 6 hr/da, 5 da/wk for 2 weeks showed no toxicologically significanttreatment-related effects on body weights; clinical chemistry,hematology, or urinalysis parameters; neurology (dogs only wereexamined); gross pathology or histopathology. The only treatment-relateddifferences in organ or relative organ weights (in rats or dogs)were slight, but statistically significant increases in liverto body weight ratios of male rats exposed to 4000 or 10 000ppm EtCI (4.9 and 7.5% respectively). Liver non-protein sulfhydryl(NPSH) concentration was measured in male Fischer rats and maleB6C3F1 mice that were exposed for 6 hours to 0,1600,4000 or10 000 ppm EtCl (mice were exposed to 0 or 4000 ppm EtCl only).Liver NPSH, measured 1/2 hr post exposure, was less than controlvalues in 4000 ppm exposed rats (88% of control value), 4000ppm exposed mice (64%), and 10 000 ppm exposed rats (89%). Theslight decreases in rat liver NPSH seem consistent with theincreased liver to body weight ratios. The toxicity data indicatethat 2-week repeated exposures to EtCl concentrations that wereup to 10 times the current A.C.G.I.H. T.L.V. (1000 ppm) causedminimal treatment-related effects in dogs and rats.     

Inhalation Toxicity of Phosphine for Fischer 344 Rats and B6C3F1 Mice

Abstract

Because of the potential increased use of phosphine (PH₃) as a fumigant and the lack of adequate toxicity data, short-term inhalation studies were conducted to characterize the toxicity of PH₃ for Fischer 344 (F344) rats and B6C3F1 mice. Male rats and mice were exposed to 0, 1, 5, or 10 ppm PH₃ for up to 4 days, and males and females to 0, 1.25, 2.5, or 5 ppm for 2 wk. In the 4-day study, all rats died by the end of the third exposure to 10 ppm, and all mice were euthanized in moribund condition after the fourth exposure to 10 ppm. Clinical pathology data were obtained only for mice, due to early mortality of rats. There were no significant treatment-related effects in hematological indices in mice exposed to 1 or 5 ppm; at 10 ppm there was a moderate anemia, and leukocyte counts were significantly decreased. There were significant biologically relevant increases in serum activity of alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) and in the concentration of urine nitrogen (UN) at 10 ppm. Flectrophoretic evaluation of hemoglobin from mice exposed to 10 ppm did not reveal any differences in banding patterns from controls. Moribund mice euthanized after 4 exposures to 10 ppm had minimal to mild degeneration and necrosis of the renal tubule epithelium, minimal myocardial degeneration, and minimal to mild subcapsular foci of hemorrhage and necrosis in the liver. Bound PH₃ could not be detected in blood, lung, liver, or kidney of mice or lungs of rats exposed to 10 ppm for 3–4 days. There were no treatment-related mortalities in rats or mice exposed for 2 weeks. Lung weights of male rats and mice were significantly decreased and heart weights of female rats and mice were significantly increased after 2 wk of exposure to 5 ppm. Slight but statistically significant increases were observed in serum UN in male mice exposed to 5 ppm. There was no microscopic evidence of treatment-related effects in any of the tissues examined from rats or mice exposed to 5 ppm for 2 wk. Bound PH₃ could not be detected in blood, lung, liver, or kidney of mice or rats exposed to 5 ppm for 2 wk. These studies demonstrated that PH₃ inhalation does not cause a specific target organ toxicity in the B6C3F1 mouse or F344 rat, and that the primary hazard of subchronic inhalation in these species is lethality.     

Inhalation Studies in Rats Exposed to Dimethylacetahide (DMAc) from 3 to 12 Hours Per Day

ABSTRACT

Male rats were exposed by inhalation from 10 to 300 ppm Dimethylacetamide (DMAc) for either 3, 6, or 12 hrs/day for a total of 10 exposures (5 exposures, 2 rest days, 5 exposures). Rats were observed daily for signs of DMAc-related effects, growth was monitored by body weights, clinical laboratory tests and microscopic examination of the liver, testes epididymides, and nasal passages were conducted. One half of the rats in each group was allowed a 14-day post-exposure period to evaluate the reversibility of DMAc-induced changes. No clinical signs of toxicity or DMAc-related gross changes at necropsy were seen in any of the rats although 1 rat exposed to 300 ppm for 12 hours per day died following the seventh exposure. Slight (< 5%) decreases in body weight gain were seen in rats exposed to 300 ppm for 6 or 12 hrs/day. Serum cholesterol levels were elevated in rats exposed to either 100 or 300 ppm (all exposure durations) and in rats exposed to 30 ppm for 12 hours. Total serum protein concentrations were increased in rats exposed for 12 hours/day to either 30, 100, or 300 ppm. Hepatocellular hypertrophy together with margination of hepatocellular cytoplasmic contents and lipid-like cytoplasmic vacuolation in hepatocytes were seen microscopically only in rats exposed for 12 hours/day to 300 ppm. Recovery from these liver changes was not complete after 14-day post-exposure period. No evidence of either testicular damage or irritation to the upper respiratory tract was seen.     

Environmental tobacco smoke at home and in public places prior to smoking ban enforcement: Assessment by hair analysis in a population of young adult students

Despite inititatives to reduce tobacco consumption, smoking remains a primary cause of death for both smokers and nonsmokers exposed to environmental tobacco smoke (ETS). The characteristics of some specific groups can make them more exposed to ETS or limit the benefit of prevention measures. This study investigated determinants of ETS in a population of young adult students, considered at higher risk of exposure due to their specific lifestyle. This cross-sectional study involved 90 students aged 20 ± 1.7 years, from the University of Luxembourg, prior to the smoking ban enforcement in public places in the country. Participants reported their tobacco consumption and exposure to ETS at home and/or in public places, and provided a hair sample analyzed for nicotine and cotinine. Nicotine and cotinine were significantly higher in smokers than in nonsmokers' hair in general (median: 2.6 vs. 0.9 ng/mg and 87.1 vs. 22.5 pg/mg respectively). However, nonsmokers exposed to ETS at home and in public places had comparable concentrations to smokers (nic = 2.2 ng/mg; cot = 56.2 pg/mg), whereas unexposed nonsmokers presented significantly lower values (nic = 0.4 ng/mg, cot = 8.5 pg/mg). Nonsmokers exposed to ETS only at home presented higher values than nonsmokers only exposed in public places (nic: 1.3 vs. 0.8 ng/mg, cot: 70.4 vs. 15.0 pg/mg). The study shows the widespread exposure to ETS in this population, the importance of exposure assessment, and the relevance of hair analysis for this purpose. Results suggest that ETS can lead to equivalent exposure to active smoking and that exposure at home can highly contribute to ETS, which is not solved by smoking ban in public places.     

Inhalation Toxicity Study of Formamide in Rats

Formamide is a widely used solvent for the manufacture and processingof plastics, and the possibility for inhalation exposure existsfor workers. To assess the toxicity of repeated inhalation ofsublethal concentrations of formamide, three groups of 10 maleCrl:CD BR rats each were exposed nose-only for 6 hr/day, 5 days/weekfor 2 weeks to design concentrations of 100, 500, or 1500 ppmof formamide vapor in air. A control group of 10 male rats wasexposed simultaneously to air only. At the end of the exposureperiod, blood and urine samples were collected for clinicalanalyses, and 5 rats per group were killed for pathologic examination.The remaining 5 rats per group were retained for a 14-day postexposureobservation (recovery) period and then subjected to the sameclinical and pathologic examinations. Male rats exposed to 1500ppm had significantly depressed body weights and body weightgains during the exposure and recovery periods compared to controls.Clinical pathologic examinations revealed that decreased plateletand/or lymphocyte counts were observed in rats exposed to 500or 1500 ppm of formamide. Pathologic examinations revealed compound-relatedmicroscopic changes in the kidneys of rats exposed to 1500 ppmformamide. Minimal to severe necrosis and regeneration of renaltubular epithelial cells were observed principally in the outerstripe of the outer medulla and in cortical medullary rays.Based upon the hematologic and clinical chemical parametersmeasured, the no-observed-effect exposure concentration forrepeated inhalation of formamide was considered to be 100 ppm,under the conditions of this study. The findings of treatment-relatedmicroscopic lesions in the kidneys as well as increases in meanabsolute kidney weights and kidney-to-body weight ratios reflectthe target organ toxicity.     

Isobutyraldehyde Administered by Inhalation (Whole Body Exposure) for up to Thirteen Weeks or Two Years Was a Respiratory Tract Toxicant but Was Not Carcinogenic in F344/N Rats and B6C3F1 Mice

Isobutyraldehyde (a chemical structurally related to formaldehydeand used as a flavoring agent) was studied for toxicity andcarcinogenicity by exposing male and female F344/N rats andB6C3F₁ mice. Animals were exposed to isobutyraldehyde vapors6 h per day, 5 days per week for up to 13 weeks or 2 years.In the 13-week studies, groups of 10 male and 10 female F344/Nrats and B6C3F₁ mice were exposed to concentrations of 0, 500,1000, 2000, 4000, or 8000 ppm. Chemical-related body weightdepression and deaths occurred in rats and mice exposed to 4000and 8000 ppm. Necrosis of the epithelium accompanied with acuteinflammatory reaction was observed in the nasal turbinate, larynx,and trachea of rats exposed to 8000 ppm. Exposure of rats to4000 ppm resulted in metaplasia of the nasal respiratory epithelium,inflammation, degeneration of the olfactory epithelium, andosteodystrophy of the nasal turbinate bone. In the 13-week mousestudy, exposure to 8000 ppm or 4000 ppm resulted in necrosisof the epithelium lining of the nasal turbinates. Osteodystrophyof the nasal turbinate bone and squamous metaplasia of the nasalrespiratory epithelium were noted in mice exposed 4000 ppm.Degeneration of the olfactory epithelium was noted in malesexposed 2000 ppm and in females exposed to 4000 ppm. In the2-year studies, groups of 50 male and 50 male F344/N rats andB6C3F1 were exposed to concentrations isobutyraldehyde vaporsof 0, 500, 1000, or 2000 ppm 6 h per day, 5 days per week. Therewere no differences in survival rates or mean body weights betweenexposed groups and control rats. Survival of male mice exposedto 2000 ppm and mean body weights of female mice exposed to1000 or 2000 ppm were lower than those of the of the controls.No increase in neoplasm incidence was observed in rats and micein the 2-year studies that could be attributed to isobutyraldehydeexposure. Chemical-related nonneoplastic lesions were limitedto the nose of rats and mice. They included squamous metaplasiaof the respiratory epithelium (rats), suppurative inflammation(rats), and olfactory epithelial degeneration (rats and mice)at 1000 and 2000 ppm.