13-WEEK INHALATION TOXICITY STUDY (INCLUDING 6- AND 13-WEEK RECOVERY PERIODS) WITH AMMONIUM PERSULFATE DUST IN ALBINO RATS

The subchronic inhalation toxicity of ammonium persulfate was characterized using Sprague-Dawley rats (20/sex/group) at respirable dust concentrations of 0, 5.0, 10.3, and 25 mg/m 3. Whole-body exposures were conducted 6 h/day, 5 days/wk for 13 wk. Gravimetric airborne test material samples were taken daily and particle size samples were taken weekly from each exposure chamber for analysis. Ten animals/sex/group were necropsied after 13 wk of exposure, and 5 animals/sex/group were held for 6- and 13-wk recovery periods. Animals were observed for clinical signs. Effects on body weight, food consumption, clinical chemistry and hematology, ophthalmologic parameters, organ weights, gross lesions, and histopathology were evaluated. There were no exposure-related deaths during the study. Rales and increased respiration rate were noted in both males and females in the 25 mg/m 3 group, and in a few animals in the 10.3 mg/m 3 group. The incidence of these clinical signs decreased to zero during the first few weeks of the recovery period. Body weights for both males and females in the 25 mg/m 3 group were significantly depressed during most of the exposure period compared to the control group. By the end of the recovery period, body weights for the exposed animals were similar to the control group values. Lung weights were elevated in the 25 mg/m 3 group after 13 wk of exposure, but were similar to controls at 6 wk postexposure. Irritation of the trachea and bronchi/bronchiole was noted microscopically after 13 wk of exposure to 25 mg/m 3. These lesions had recovered by 6 wk postexposure. Based on the results of this study, the no-observed-adverse-effect level (NOAEL) was 10.3 mg/m 3, while the no-observed-effect level (NOEL) for exposure of rats to a dust aerosol of ammonium persulfate was 5.0 mg/m 3 .     

NTP toxicology and carcinogensis studies of vanadium pentoxide (CAS No. 1314-62-1) in F344/N rats and B6C3F1 mice (inhalation)

Vanadium pentoxide, commercially the most important compound of vanadium, presents a potential occupational hazard during the cleaning of oil-fired boilers and furnaces, the handling of catalysts, and during the refining, processing, or burning of vanadium-rich mineral ores or fossil fuels. Vanadium pentoxide was nominated for study by the National Cancer Institute as a representative of the metals class study. Male and female F344/N rats and B6C3F1 mice were exposed to vanadium pentoxide (99% pure) by inhalation for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood. 16-DAY STUDY IN RATS: Groups of five male and five female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Three males in the 32 mg/m(3) group died before the end of the study. Mean body weights of males and females exposed to 8 mg/m(3) or greater were less than those of the chamber controls. Clinical findings included rapid respiration and hypoactivity in rats exposed to 16 or 32 mg/m(3). Relative lung weights of 4 mg/m(3) or greater males and 2 mg/m(3) or greater females were significantly greater than those of the chamber controls. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 16-DAY STUDY IN MICE: Groups of five male and five female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. All males exposed to 32 mg/m(3) and one 8 mg/m(3) male died or were killed moribund before the end of the study. Mean body weights of 16 mg/m(3) males and 8 mg/m(3) or greater females were significantly less than those of the chamber controls, and the 32 mg/m(3) females lost weight during the study. Absolute and relative lung weights of 4 mg/m(3) or greater males and all exposed groups of females and liver weights of 16 mg/m(3) males were significantly greater than those of the chamber controls. The mediastinal lymph nodes were enlarged in 4, 8, and 16 mg/m(3) males and females, and lymphoid hyperplasia was confirmed histologically. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. Seven males and three females exposed to 16 mg/m(3) died during the study. Mean body weights were significantly less in males exposed to 4 mg/m(3) or greater and in females exposed to 16 mg/m(3). Abnormal breathing, thinness, lethargy, abnormal posture, and ruffled fur were observed in rats exposed to 16 mg/m(3). Hematology results indicated that exposure of rats to vanadium pentoxide induced a microcytic erythrocytosis in males and females. Absolute and relative lung weights were significantly greater for 4 mg/m(3) or greater males and females than for the chamber controls as were the relative lung weights of 2 mg/m(3) males. The estrous cycle of females exposed to 8 mg/m(3) was significantly longer than that of the chamber control group, and the number of cycling females in the 16 mg/m(3) group was reduced. The incidences of several nonneoplastic lesions of the lung and nose were significantly increased in males and females exposed to 2 mg/m(3) or greater. Data from pulmonary function analyses indicated that a restrictive lung disease was present in male and female rats exposed to 4 mg/m(3) or greater, while an obstructive lung disease was present only in the 16 mg/m(3) groups. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. One male exposed to 16 mg/m(3) died before the end of the study. Mean body weights of 8 and 16 mg/m(3) males and 4 mg/m(3) or greater females were significantly less than those of the chamber controls. Absolute and relative lung weights of males and females exposed to 4 mg/m(3) or greater were significantly greater than those of the chamber controls. The epididymal spermatozoal motility of males exposed to 8 or 16 mg/m(3) was significantly decreased. Some mice exposed to 2 or 4 mg/m(3) had inflammation of the lung, and all mice exposed to 8 or 16 mg/m(3) had inflammation and epithelial hyperplasia of the lung. 16-DAY SPECIAL STUDY IN RATS: Groups of 60 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, or 2 mg/m(3) and groups of 40 female rats were exposed to 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia was observed in most rats exposed to 2 or 4 mg/m(3) on days 6 and 13. Histiocytic infiltration and inflammation occurred in a time- and concentration-related manner. Cell turnover rates were increased in the terminal bronchioles on days 6 and 13 and in the alveoli in the 4 mg/m(3) group on day 6 and in all exposed groups on day 13. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 4.42 to 4.96 days. 16-DAY SPECIAL STUDY IN MICE: Groups of 60 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, or 4 mg/m(3) and groups of 40 female mice were exposed to 8 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia occurred with similar incidences and severities among the exposed groups on days 6 and 13, and time- and concentration-related increases in the incidences of interstitial inflammation and histiocytic infiltration also occurred in these groups. Cell turnover rates were increased in the terminal bronchioles on day 6 and remained greater than those of the chamber controls on day 13. In the alveoli, cell turnover rates were increased in an exposure concentration-related manner on day 13; cell turnover rates were increased only in the 8 mg/m(3) group on day 6. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 2.40 to 2.55 days. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 0.5, 1, or 2 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival and body weights of males and females were generally similar to those of the chamber controls. Mean body weights of females exposed to 2 mg/m(3) were less than those of the chamber controls throughout the study. Alveolar/bronchiolar neoplasms were present in exposed groups of male rats, and the incidences often exceeded the historical control ranges. Alveolar/bronchiolar adenomas were present in 0.5 and 1 mg/m(3) females; one 2 mg/m(3) female also had an alveolar/bronchiolar carcinoma. The incidence of alveolar/bronchiolar adenoma in the 0.5 mg/m(3) group was at the upper end of the historical control ranges. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female rats, and the severities of these lesions generally increased with increasing exposure concentration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, or 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival of 4 mg/m(3) males was significantly less than that of the chamber controls. Mean body weights of 4 mg/m(3) males and all exposed groups of females were generally less than those of the chamber controls throughout the study, and those of males exposed to 2 mg/m(3) were less from week 85 to the end of the study. Many mice exposed to vanadium pentoxide were thin, and abnormal breathing was observed in some mice, particularly those exposed to 2 or 4 mg/m(3). The incidences of alveolar/bronchiolar neoplasms were significantly increased in all groups of exposed males and females. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female mice, and the severities of these lesions generally increased with increasing exposure concentration. Bronchial lymph node hyperplasia was present in many exposed females. MOLECULAR ONCOLOGY STUDIES: K-ras codon 12 mutation and loss of heterozygosity on chromosome 6 were detected in vanadium pentoxide-induced alveolar/bronchiolar carcinomas from mice. GENETIC TOXICOLOGY: Vanadium pentoxide was not mutagenic in Salmonella typhimurium strain TA97, TA98, TA100, TA102, or TA1535, with or without induced rat or hamster liver S9 enzymes. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of vanadium pentoxide in male F344/N rats and equivocal evidence of carcinogenic activity of vanadium pentoxide in female F344/Nrats based on the occurrence of alveolar/bronchiolar neoplasms. There was clear evidence of carcinogenic activity of vanadium pentoxide in male and female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. (ABSTRACT TRUNCATED)     

Dose-response study with N-nitrosodiethanolamine in F344 rats

A dose-response study of the carcinogenicity of N-nitrosodiethanolamine was conducted in F344 rats. The nitrosamine was administered in drinking-water at a controlled rate (20 ml/rat/day, 5 days/wk) to groups of 16 or 20 rats of each sex. The doses administered were as follows: 2500 mg/litre drinking-water for 45-wk, 1000 mg/litre for 50 wk, 400 mg/litre for 50 wk and 400 mg/litre for 75 wk. Almost all of the treated animals died with hepatocellular carcinomas, of which 20–45% metastasized in each group. The females in each treatment group tended to die earlier, because they received a higher dose per unit body weight, but for each sex there was a dose-related decrease in survival as the carcinogen dose increased. There was a considerable incidence of tumours of the nasal cavity. The incidence of these tumours tended to be higher in males than in females and might be sex- or lifespan-related. A number of rats had cholangiocarcinomas in the liver and there were a few kidney tumours and tumours of the oesophagus in animals given the higher doses. None of these tumours was seen in the untreated controls of either sex, almost all of which outlived the treated animals. It is concluded that N-nitrosodiethanolamine is a carcinogen of considerable potency in rats.     

Acute and sub-acute inhalation toxicity of germanium metal powder in rats

An acute (4-hr) and a sub-acute (4-wk) inhalation toxicity study of germanium metal powder (purity 99.8%, mean particle size 2.0-2.4 microns) were carried out in young adult Wistar rats. Exposure of five male and five female rats to 3.86 or 5.34 g/m3 for 4 hr resulted in the death of one rat at each exposure level. Four groups of five male and five female rats were exposed to 0, 9.9, 65.1 or 251.4 mg/m3 for 6 hr/day, 5 days/wk for 30 days. Two additional (recovery) groups of five male and five female rats exposed to 0 or 251.4 mg/m3 were kept untreated for 31 days after exposure. At the end of the treatment period, fasting blood glucose was decreased in males exposed to the high concentration. In females of this group, blood creatinine and urea levels, and urine volumes were increased, but urine density was decreased. Increased blood creatinine levels and urine volume and decreased urine density were also observed in females exposed to 65.1 mg/m3. The absolute and relative lung weights were increased in rats in the mid-and high-concentration groups. Histopathological examination revealed: accumulation of particulate material in the lungs of all treated groups, accumulation of alveolar macrophages in the mid- and high-concentration groups, and alveolitis mainly in the high-concentration group. After the 4-wk recovery period, urine volume was increased in males that had been exposed to germanium. In exposed rats of both sexes, lung weights were still increased and histopathological changes were present, but to a lesser extent than at the end of the exposure period. It was concluded that the 4-hr LC50 value of germanium metal powder in rats is greater than 5.34 g/m3. The no-adverse-effect level in the 4-wk study was 9.9 mg/m3 air.     

NTP technical report on the toxicology and carcinogenesis studies of Stoddard Solvent IIC (Cas No. 64742-88-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Stoddard solvent (white spirit/mineral spirit) is the most widely used solvent in the paint industry. It is used as a dry cleaning agent; as an extraction, cleaning, and degreasing solvent; and as a solvent in aerosols, paints, wood preservatives, asphalt products, lacquers, and varnishes. Stoddard solvent IIC was nominated by the International Union, United Auto Workers, for carcinogenicity testing because of the large volume used in industrial and other settings. Male and female F344/N rats and B6C3F1 mice were exposed to Stoddard solvent IIC (greater than 99% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 16 days. All rats survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Liver weights of males exposed to 550 mg/m3 or greater and of females exposed to 275 mg/m3 or greater were increased. Minimal diffuse cytoplasmic vacuolization of hepatocytes of the liver occurred in all females exposed to 2,200 mg/m3. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 17 days. All mice survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Liver weights of males and females exposed to 275 mg/m3 or greater were significantly increased. Cytomegaly of the liver occurred in all males and females exposed to 2,200 mg/m3. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 14 weeks. All rats survived to the end of the study, and the final mean body weight of females exposed to 275 mg/m3 was greater than that of the chamber controls. The relative kidney, liver, and testis weights of all exposed groups of males and the absolute kidney weights of males exposed to 550 mg/m3 or greater were increased. The sperm motility of 550 mg/m3 or greater males was significantly decreased. The incidences of renal tubule granular casts were significantly increased in males exposed to 550 mg/m3 or greater, and the severities of renal tubule hyaline droplet accumulation, granular casts, and regeneration increased with increasing exposure concentration in males. The incidences of goblet cell hypertrophy of the nasal respiratory epithelium in males and females exposed to 2,200 mg/m3 were significantly increased. Sperm motility was decreased in males exposed to 550 mg/m3 or greater. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 14 weeks. Mean body weights of exposed groups were similar to those of the chamber controls, but liver weights of males exposed to 2,200 mg/m3 were significantly increased. The sperm motility of 2,200 mg/m3 males was significantly decreased. This reduction in sperm motility, while statistically significant, is probably of modest importance as studies in mice have found that fertility is unaffected by motility decreases of less than 40%. The incidences of hematopoietic cell proliferation of the spleen in all exposed groups of females were greater than that in the chamber controls. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138 (males), 550, 1,100, or 2,200 (females) mg/m3, 6 hours per day, 5 days per week for 104 to 105 weeks. Additional groups of 10 males and 10 females were exposed to the same concentrations for 3 months for renal toxicity analyses. Survival in the top exposure concentration groups of males and females was significantly less than that of the chamber controls. Mean body weights of exposed males and females were similar to those of the chamber controls. Cell proliferation analyses were performed in the left kidney of males and females after 3 months of exposure. The mean numbers of labeled cells and the labeling indices in males exposed to 550 and 1,100 mg/m3 were significantly increased. The amount of alpha2u-globulin in the right kidney of males increased with increasing exposure concentration. Also, the incidences of granular casts and cortical tubule degeneration and regeneration were generally increased in exposed males, as was the severity of hyaline droplets. These effects did not occur in females. At 2 years, the incidences of benign and benign or malignant pheochromocytoma (combined) of the adrenal medulla occurred with positive trends in males, and the incidences in the 550 and 1,100 mg/m3 groups were significantly increased. Due to increased incidences of renal tubule hyperplasia in males at 2 years, extended kidney evaluations were conducted; a slightly increased incidence of renal tubule adenoma occurred in the 1,100 mg/m3 group. Nonneoplastic lesions related to Stoddard solvent IIC exposure occurred in the kidney of males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 105 weeks. Survival of exposed mice was similar to that of the chamber controls. Mean body weights of exposed females were greater than those of the chamber controls. The incidences of hepatocellular adenoma occurred with a positive trend in females, and the incidence of multiple hepatocellular adenoma in females exposed to 2,200 mg/m3 was significantly increased. However, the incidences of hepatocellular adenoma or carcinoma (combined) and hepatocellular carcinoma alone in exposed males and females were not significantly increased. GENETIC TOXICOLOGY: Stoddard solvent IIC was tested for mutagenicity in Salmonella typhimurium strains TA97, TA98, TA100, and TA1535, with and without S9 metabolic activation enzymes; all results were negative. In vivo, the frequency of micronucleated erythrocytes was assessed in peripheral blood samples from male and female B6C3F1 mice after 3 months of inhalation exposure to Stoddard solvent IIC, and results were negative. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of Stoddard solvent IIC in male F344/N rats based on increased incidences of adrenal medulla neoplasms; the slightly increased incidences of renal tubule adenoma may have been related to Stoddard solvent IIC exposure. There was no evidence of carcinogenic activity of Stoddard solvent IIC in female F344/N rats exposed to 550, 1,100, or 2,200 mg/m3. There was no evidence of carcinogenic activity of Stoddard solvent IIC in male B6C3F1 mice exposed to 550, 1,100, or 2,200 mg/m3. There was equivocal evidence of carcinogenic activity of Stoddard solvent IIC in female B6C3F1 mice based on increased incidences of hepatocellular adenoma; this slight increase was associated with increased body weight in exposed females. Exposure of male rats to Stoddard solvent IIC resulted in nonneoplastic lesions of the kidney characteristic of alpha2u-globulin accumulation.     

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).     

TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS: INHALATION SUBCHRONIC TOXICITY/NEUROTOXICITY STUDY OF A LIGHT ALKYLATE NAPHTHA DISTILLATE IN RATS

A 13-wk inhalation study was conducted with Sprague-Dawley CD rats ( 12/sex/ group) were exposed by inhalation for 13 weeks to a light alkylate naphtha distillate (LAND-2, C-C ; average molecular weight 89.2) at actual average concentrations of 0 (room 4 10 air), 668, 2220, or 6646 ppm, 6 h/d, 5 d/wk; 12 additional rats/sex in the control and high dose groups were held after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, during 5, 9, and 14 wk of the study, and after the 4-wk recovery period. Wholebody perfusion and microscopic examination of selected organs and nervous tissue from the control and high dose rats were conducted at the end of exposure. No testrelated mortality or effects on physical signs, body weight, or food consumption were observed. Statistically significant increases in absolute and relative kidney weights in high-exposure males correlated with microscopically observed hyaline droplet formation and renal nephropathy, effects in male rats that are not toxicologically significant for humans. Increased liver weights in both sexes at the highest dose had no microscopic correlate and appeared reversible after the 4-wk recovery period. Exposure to LAND-2 at any dose did not produce neurotoxicity measured by MA, FOB, or neuropathology. The no-observed-effects level (NOEL) for LAND-2 was 2220 ppm for subchronic toxicity and 6646 ppm for neurotoxicity.     

Thirteen-week inhalation toxicity of 1,4-dioxane in rats

Thirteen-week inhalation toxicity of 1,4-dioxane was examined by repeated inhalation exposure of male and female F344 rats to 0 (control), 100, 200, 400, 800, 1600, 3200, or 6400 ppm (v/v) 1,4-dioxane vapor for 6 h/day and 5 days/wk. All the 6400-ppm-exposed males and females died during the first week. Terminal body weight decreased, and relative weights of liver, kidney, and lung increased. AST increased in the 200 ppm-and 3200-ppm-exposed females, and ALT increased in the 3200-ppm-exposed males and females. Nuclear enlargement of nasal respiratory epithelial cells occurring in the 100-ppm-exposed males and females was the most sensitive, followed by the enlarged nuclei in the olfactory, tracheal, and bronchial epithelia. 1,4-Dioxane-induced liver lesions occurred at higher exposure concentrations than the nasal lesions did, and were characterized by single-cell necrosis and centrilobular swelling of hepatocytes in males and females. Glutathione S-transferase placental form (GST-P) positive liver foci were observed in the 1600-ppm-exposed females and 3200-ppm-exposed males and females, which are known as a preneoplastic lesion in rat hepatocarcinogenesis. Plasma levels of 1,4-dioxane increased linearly with an increase in the concentrations of exposure to 400 ppm and above. The enlarged nuclei in the nasal epithelia and the GST-P-positive liver foci were discussed in light of the possible development of nasal and hepatic tumors by long-term inhalation exposure to 1,4-dioxane. A lowest-observed-adverse-effect level (LOAEL) was determined at 100 ppm for the nasal endpoint in both male and female rats.     

Subchronic nose-only inhalation study of propylene glycol in Sprague-Dawley rats

Groups of nineteen Sprague-Dawley rats of each sex were exposed by a nose-only inhalation to 0.0, 0.16, 1.0 or 2.2 mg propylene glycol/litre air, for 6 hr/day, 5 days/wk for 90 days. There were no significant differences in respiratory rates, minute volumes or tidal volumes between any of the groups during aerosol exposure. The uniformity of respiratory parameters between dose groups implied that the delivered doses were proportional to the exposure concentrations. The mean terminal body weights were not significantly different from controls for any group of male animals. The mean body weights of the females exposed to 2.2 mg/litre were significantly less than those of female controls from day 50 onwards. This effect, in female rats, was consistent with a decrease in feed consumption for the high-exposure female rats beginning on study day 43. Statistically significant differences between the treated and control groups in certain haematological parameters, serum enzyme activities, other serum chemistry parameters and organ weights did not show clear dose relationships. There was a significant increase in the number of goblet cells or an increase in the mucin content of the existing goblet cells in the nasal passages of the medium- and high-exposure animals. Exposure to the above concentrations of propylene glycol caused nasal haemorrhage and ocular discharge in a high proportion of animals, possibly as a result of dehydration of the nares and eyes.     

Subacute inhalation toxicity of a medium-boiling coal liquefaction product (154-378 degrees C) in the rat [Part III

The short-term inhalation toxicity of a medium-boiling coal liquefaction product (CLP) was investigated in the rat. Groups of 5 male and 5 female Sprague-Dawley rats were exposed to CLP aerosols at 25 mg/m3 (low dose) or 100 mg/m3 (high dose) 6 h/d, 5 d/w, for 4 wk. The control group was exposed to filtered air while the positive control received diesel fuel aerosols at 100 mg/m3. Male rats exposed to high-dose CLP aerosols exhibited growth depression and increased hepatic aminopyrine demethylase activity compared to control animals. High-dose females had decreased hemoglobin content and hematocrit values. These biochemical and hematological effects were not observed in animals of either sex treated with the diesel fuel. No other biochemical and hematological changes were observed. Mild histological changes occurred in the liver and thyroid of rats treated with CLP and diesel fuel aerosols. Based on the data presented, inhalation of CLP aerosols resulted in toxicological effects that were similar to those caused by dermal exposure.     

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 mu m 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/m³ for the 250-, 500-, and 1000-mg/m³ groups, respectively. The mean MMADs were 2.83, 2.90, and 4.09 mu m for the 250-, 500-, and 1000-mg/m³ 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/m³ group at sacrifice were the only exposure-related clinical signs observed. Increased lung weights in the 500- and 1000-mg/m³ 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/m³ with mean MMADs of 3.09, 2.64, and 2.67 mu m and sigma_g values ranging from 3.54 to 3.90 for exposure concentrations of 30, 100, and 300 mg/m³, respectively. The only findings at the 90-day sacrifice were increased lung weights for the males and females in the 300-mg/m³ group and males in the 100-mg/m³ group. For the 6- wk recovery sacrifice of the females, the lung weights for the 300- and 100-mg/m³ 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/m³ 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/m³ for 2 h had increased lung weights. However, no effects were observed in the 30-mg/m³ exposure group. Thus, under the conditions of the present 90-day study, a no-observable-effect level (NOEL) was found to be 30 mg/m³.     

Toxicology and carcinogenesis studies of indium phosphide (CAS No. 22398-90-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Indium phosphide is used to make semiconductors,injection lasers, solar cells, photodiodes, and light-emittingdiodes. Indium phosphide was nominated for study because of its widespread use in the microelectronics industry, the potential for worker exposure,and the absence of chronic toxicity data. Male and female F344/N rats and B6C3F1 mice were exposed to indium phosphide (greater than 99% pure) by inhalation for 14 weeks or 2 years. The frequency of micronuclei was determined in the peripheral blood of mice exposed to indium phosphide for 14 weeks. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to particulate aerosols of indium phosphide with amass median aerodynamic diameter of approximately 1.2 microm at concentrations of 0, 1, 3, 10, 30, or 100 mg/m3 by inhalation, 6 hours per day, 5 days per week (weeks 1 through 4 and weeks 10 through 14) or 7 days per week (weeks 5 through 9) to accommodate a concurrent teratology study. One male in the 100 mg/m3 group died before the end of the study. Body weight gains of all males and females exposed to 100 mg/m3 were less than those of the chamber controls. As a result of indium phosphide exposure, the lungs of all exposed rats had a gray to black discoloration and were significantly enlarged, weighing 2.7- to 4.4-fold more than those of the chamber controls. Indium phosphide particles were observed throughout the respiratory tract and in the lung-associated lymph nodes. A spectrum of inflammatory and proliferative lesions generally occurred in the lungs of all exposed groups of rats and consisted of alveolar proteinosis, chronic inflammation, interstitial fibrosis, and alveolar epithelial hyperplasia. Pulmonary inflammation was attended by increased leukocyte and neutrophil counts in the blood. The alveolar proteinosis was the principal apparent reason for the increase in lung weights. Indium phosphide caused inflammation at the base of the epiglottis of the larynx and hyperplasia of the bronchial and mediastinal lymph nodes. Exposure to indium phosphide affected the circulating erythroid mass. It induced a microcytic erythrocytosis consistent with bone marrow hyperplasia and hematopoietic cell proliferation of the spleen. Hepatocellular necrosis was suggested by increased serum activities of alanine aminotransferase and sorbitol dehydrogenase in all exposed groups of males and in 10 mg/m3 or greater females and was confirmed microscopically in 100 mg/m3 males and females. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to particulate aerosols of indium phosphide with a mass median aerodynamic diameter of approximately 1.2 microm at concentrations of 0, 1, 3, 10, 30, or 100 mg/m3 by inhalation, 6 hours per day, 5 days per week (weeks 1 through 4 and weeks 10 through 14)or 7 days per week (weeks 5 through 9). Although the effects of indium phosphide exposure were similar in rats and mice, mice were more severely affected in that all males and females in the 100 mg/m3 groups either died or were removed moribund during the study. One male and three females in the 30 mg/m3 group were also removed before the end of the study. In general, body weight gains were significantly less in males and females exposed to 3 mg/m3 or greater compared to those of the chamber controls. Mice exposed to 30 or 100 mg/m3 were lethargic and experienced rapid, shallow breathing. As in rats, lungs were discolored and enlarged 2.6- to 4.1-fold greater than those of chamber controls due to the exposure-induced alveolar proteinosis. Indium phosphide particles were observed in the nose, trachea,larynx, and lymph nodes of some exposed males and females. Alveolar proteinosis, chronic active inflammation,interstitial fibrosis, and alveolar epithelial hyperplasia were observed; these effects were more severe than in rats. Hyperplasia in the bronchial lymph nodes and squamous metaplasia, necrosis, and suppurative inflammation of the larynx were observed in some exposed males and females. Exposure to indium phosphide induced a microcytic erythrocytosis which was consistent with the observed hematopoietic cell proliferation of the spleen.2-YEAR STUDY IN RATS Groups of 60 male and 60 female rats were exposed to particulate aerosols of indium phosphide at concentrations of 0, 0.03, 0.1, or 0.3 mg/m3, 6 hours per day,5 days per week, for 22 weeks (0.1 and 0.3 mg/m3 groups) or 105 weeks (0 and 0.03 mg/m3 groups). Animals in the 0.1 and 0.3 mg/m3 group were maintained on filtered air from exposure termination at week 22 until the end of the studies. Ten males and 10 females per group were evaluated at 3 months. 3-Month Interim Evaluation: Exposure to indium phosphide for 3 months caused a microcytic erythrocytosis and also caused enlarged lungs and lesions in the respiratory tract and lung associated lymph nodes. Although qualitatively similar to those observed in the 14-week studies, these effects were considerably less severe. However, the lesions in the lungs of rats exposed to 0.1 or 0.3 mg/m3 were considered sufficiently severe that exposure was discontinued in these groups, and the groups were allowed to continue unexposed for the remainder of the study. Survival, Body Weights, and Clinical Findings: Exposure to indium phosphide had no effect on survival or body weight gain. During the last 6 months of the study, rats in the 0.03 and 0.3 mg/m3 groups became lethargic and males breathed abnormally. Pathology Findings: At 2 years, exposure to indium phosphide caused increased incidences of alveolar/bronchiolar adenomas and carcinomas in rats. Squamous cell carcinoma of the lung occurred in four male rats exposed to 0.3 mg/m3. As observed in the 14-week study and at the 3-month interim evaluation, a spectrum of inflammatory and proliferative lesions of the lung were observed in all exposed groups of males and females;however, the extent and severity of the lesions were generally greater and included atypical hyperplasia,chronic inflammation, alveolar epithelial hyperplasia and metaplasia, alveolar proteinosis, and interstitial fibrosis. Exposure to indium phosphide also caused increased incidences of benign and malignant pheochromocytomas of the adrenal gland in males and females. Marginal increases in the incidences of mononuclear cell leukemia in males and females, fibroma of the skin in males, and carcinoma of the mammary gland in females may have been related to exposure to indium phosphide. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female mice were exposed to particulate aerosols of indium phosphide at concentrations of 0, 0.03, 0.1, or 0.3 mg/m3, 6 hours per day,5 days per week, for 21 weeks (0.1 and 0.3 mg/m3 groups) or 105 weeks (0 and 0.03 mg/m3 groups). Animals in the 0.1 and 0.3 mg/m3 groups were maintained on filtered air from exposure termination at week 21 until the end of the studies. Ten males and 10 females per group were evaluated at 3 months. 3-Month Interim Evaluation:Exposure to indium phosphide for 3 months affected the circulating erythroid mass and caused enlarged lungs and lesions in the respiratory tract and lung associated lymph nodes. These effects, although qualitatively similar to those observed in the 14-week studies, were considerably less severe. However, the lesions in the lungs of mice exposed to 0.1 mg/m3 and greater were considered sufficiently severe that exposure was discontinued in these groups and the groups were allowed to continue unexposed for the remainder of the study. Survival and Body Weights: In general, exposure to indium phosphide for 2 years reduced survival and body weight gain in exposed males and females. Pathology Findings:At 2 years, exposure to indium phosphide caused increased incidences of alveolar/bronchiolar carcinomas in males and alveolar/bronchiolar adenomas and carcinomas in females. In addition to the alveolar proteinosis and chronic active inflammation seen at earlier time points, serosa fibrosis and pleural mesothelial hyperplasia were also present. The incidences of hepatocellular neoplasms were also significantly increased in exposed males and females. Exposed groups of males and females had increased incidences of eosinophilic foci of the liver at 2 years. Marginal increases in the incidences of neoplasms of the small intestines in male mice may have been related to exposure to indium phosphide. Exposure to indium phosphide also caused inflammation of the arteries of the heart, primarily the coronary arteries and the proximal aorta, and to a lesser extent the lung-associated lymph nodes in males and in females. TISSUE BURDEN ANALYSES: Deposition and clearance studies of indium following long term exposure of rats and mice to indium phosphide by inhalation were performed. Although there were quantitative differences in lung burden and kinetic parameters for rats and mice, qualitatively they were similar. Deposition of indium in the lungs appeared to follow a zero-order (constant rate) process. Retained lung burdens throughout the studies were proportional to exposure concentration and duration. No differences in elimination rates of indium from the lungs were observed as a function of exposure concentration in either rats or mice. These studies indicated that elimination of indium was quite slow. Mice exhibited clearance half-times of 144 and 163 days for the 0.1 and 0.3 mg/m3 groups, respectively, as compared to 262 and 291 days for rats exposed to the same concentrations. The lung deposition and clearance model was used to estimate the total amount of indium deposited in the lungs of rats and mice after exposure to 0.03 mg/m3 for 2 years or to 0.1 or 0.3 mg/m3 for 21 or 22 weeks, the lung burdens at the end of the 2-year study, and the area under lung burden curves (AUC). For both species, estimates at the end of 2 years indicated that the lung burdens in the continuously exposed 0.03 mg/m3 groups were greater than those in the 0.1 or 0.3 mg/m3 groups. (ABSTRACT TRUNCATED)     

Subacute inhalation toxicity of 2-chloro-4-toluidine in rats

This article addresses results from a 4-wk inhalation exposure study in Wistar rats with the vapor and/or aerosol atmospheres of 2-chloro-4-toluidine. Groups of 10 rats/sex were nose-only exposed to mean analytical concentrations of 19.1, 115.1, and 702.3 mg/m3 using an exposure regimen of 6 h/day and 20-22 exposures within a time period of 4 wk. These concentrations were selected based on results from a repeated 5 x 6 h/day pilot study using concentrations of 27.1, 104.8, 381.6, and 1283.7 mg/m3. In a single 4-h exposure study at the maximum tested concentration of 7620 mg/m3, 1 of 10 female rats succumbed (no mortality in males), while no mortality occurred at 3293 mg/m3. In the 1- and 4-wk studies mortality occurred at 1283.7 and 702.3 mg/m3, respectively. Rats exposed for 4 wk to 702.3 mg/m3 displayed characteristic signs of toxicity that included cyanosis, respiratory distress, and significantly decreased body weights. Rectal temperatures were significantly decreased at 115.1 mg/m3 and above. Dark and enlarged spleens occurred at 702.3 mg/m3. At this concentration, prominent treatment-related effects included methemoglobinemia, reticulocytosis, red blood cells with Heinz bodies, decreased hemoglobin, hematocrit, and red blood cell counts. Borderline evidence of erythrocytotoxicty was noticed at 115.1 mg/m3 (based on a minimal increase in Heinz bodies). Spleen and liver weights were significantly increased at 702.3 mg/m3, whereas the thymus weight was decreased at 115.1 mg/m3 and above. Microscopic changes were found in the spleen (hemosiderosis) at 702.3 mg/m3. An atrophy of the olfactory epithelium in the nasal cavities occurred at 115.1 mg/m3 and above. Clinical pathology revealed changes pathognostic of hepatic effects, although microscopic examinations did not reveal any specific changes. The no-observed-adverse-effect level (NOAEL) of the 4-wk study was 19.1 mg/m3 and is based on the predominant atrophic changes of the olfactory epithelium and the minimal to borderline erythrocytotoxic effects at 115.1 mg/m3.     

Evaluation of the subchronic and reproductive effects of a series of chlorinated propanes in the rat. I. Toxicity of 1,2,3-trichloropropane

Repeated inhalation exposure and 1-generation reproduction studies have been conducted in the rat to address the adequacy of the 10 ppm occupational exposure limit established for 1,2,3-trichloropropane (TriCP). Groups of 5 rats per sex were exposed for 6 h/d, 5 d/wk up to 4 wk to target TriCP concentrations of 0-900 ppm. Nine of 10 rats died after a single exposure at 900 ppm. Additional deaths were seen in the 300 (1 death) and 600 (3 deaths) ppm test groups. Mean body weights for all TriCP-treated groups were lower than control values. Liver weights were increased in animals of both sexes at 600 ppm and lower. For females ovary weights for the 300 and 600 ppm groups and spleen weights for the 300 ppm group were lower than those of controls. Males exhibited decreased testes weights only at the 600 ppm TriCP level (not evaluated at 900 ppm). Results of a 13-wk exposure, 6 h/d, 5 d/wk of 15 rats/sex.group to TriCP target vapor concentrations of 5, 15, or 50 ppm also resulted in liver weight increases at all test levels. Histopathologic examination showed hepatocellular hypertrophy in male rats at all TriCP levels. Other microscopic findings related to treatment in rats exposed to 15 ppm and to 5 ppm TriCP included lung hyperplasia (both sexes) and splenic extramedullary hematopoiesis (females only) and parallel observed organ weight increases. No treatment-related deaths were observed in this study, nor were there apparent effects on the hematology or clinical chemistries. Group mean body weights at 50 ppm (both sexes) and 15 ppm (females only) TriCP were reduced when compared to controls. In a 13-wk follow-up study in rats at 0, 0.5, and 1.5 ppm TriCP, no gross or microscopic findings related to treatment were found. Groups of 10 male and 20 female rats were exposed 6 h/d, 5 d/wk to 0, 5, or 15 ppm TriCP vapor during premating and mating. Females also were exposed during gestation. Low mating performance was observed in all groups of female rats including the controls, although fewer females in the 15-ppm group mated than in other study groups. Mating and fertility indices of male rats in both treated and control groups were generally low. All measured progeny indices appeared unaffected by treatment. A follow-up study of the same design was conducted at levels of 0, 0.5, and 1.5 ppm TriCP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diesel exhaust affects the abnormal delivery in pregnant mice and the growth of their young

To clarify the toxic effects of diesel exhaust (DE) on delivery in mice and on growth of young, C57Bl-strain females were exposed to 0.3, 1.0, or 3.0 mg diesel exhaust particles (DEP)/m3 or filtered clean air (control) for 4 mo (12 h/day, 7 days/wk). After exposure, some females from each group were examined by necropsy, and the remainders were mated with unexposed males. Estrous females for necropsy who had been exposed to 1.0 mg DEP/m3 had significantly lower uterine weights than the control estrous females. In the mated females, 9.1, 10.0, or 25.0% (0.3, 1.0, or 3.0 mg DEP/m3 of the pregnancies resulted in abnormal deliveries (abortion and unable delivery), but this was not significant. The rate of good nest construction by delivered females exposed to 3.0 mg DEP/m3 was significantly lower. Young were weighed at 11, 14, and 21 days, and weekly from wk 4 to 9 after birth. Body weights of male young of dams exposed to 1.0 or 3.0 mg DEP/m3 were significantly lower at 6 and 8 wk of age. Body weights of female young of dams exposed to 1.0 or 3.0 mg DEP/m3 were also significantly lower at 6, 8, and 9 wk. Vaginal orifices of young female mice whose dams were exposed to 0.3 and 1.0 mg DEP/m3 opened significantly earlier. The young were killed at 30 or 70 days during deep anesthesia, and their body weights, organ weights, and body lengths were measured. Anogenital distance (AGD) of 30-day-old males whose dams were exposed to 0.3 mg DEP/m3 was significantly shorter than that of the controls. Weights of thymus and ovary in 30-day-old females whose dams were exposed to 3.0 mg DEP/m3 were significantly lower. In 70-day-old males of dams exposed to 3.0 mg DEP/m3, body weights were significantly lower and AGD was significantly shorter. Weights of adrenals, testes, and seminal vesicles in 70-day-old males with dams exposed to 1.0 mg DEP/m3 were significantly lower. In 70-day-old females with dams exposed to DE, body weights in the 3.0-mg DEP/m3 group were significantly lower, and weights of adrenals, liver, and thymus in the 1.0-mg DEP/m3 group were significantly lower. Thymus weights in 70-day-old females with dams exposed to 0.3 mg DEP/m3 were significantly lower. Crown-rump length (CR) in 70-day-old females with dams exposed to 1.0 or 3.0 mg DEP/m3 was significantly shorter. These results show that toxic substances in DE might cause abnormal delivery in mice, and that exposed females affected the growth and sexual maturation of their young.     

Evaluation of the effects of subchronic oral administration of n-butyl maleate in Sprague-Dawley rats

n-Butyl maleate, also referred to as monobutyl maleate, is an ester of maleic acid, which is used as a counterion in the pharmaceutical industry. While substantial published data exist on short-term treatment, maleic acid-induced renal toxicity in the rat, no toxicity data are available on the monobutyl ester. This study evaluated the oral subchronic nephrotoxicity potential of n-butyl maleate administered to Sprague-Dawley rats (10/males and females/group) at doses of 0 (vehicle control), 10, 30, or 60 mg/kg/d for 2 wk. Statistically significant elevations in organ weights were noted in males at 60 mg/kg/d and included: (a) increases in absolute heart, kidney, and liver weights; (b) increased liver to body weight ratios; and (c) increased heart, kidney, liver, spleen, and epididymides to brain weight ratios. In females, statistically significant increases in organ weights were limited to increases in adrenal to brain weights at > or = 10 mg/kg/d, kidney to brain weights at > or = 30 mg/kg/d, and kidney to body weight and liver to brain weight ratios at 60 mg/kg/d. There were no macroscopic or microscopic pathology changes observed in any of the tissues examined. Importantly, light microscopic examination of the kidney was unremarkable at the end of the 2-wk dosing period with n-butyl maleate. Although lacking a histopathological correlate, resultant increases in organ weights at 60 mg/kg/d might be considered indicative of an adverse effect. However, renal perturbation induced by n-butyl maleate was mild in comparison to maleic acid-induced renal toxicity, which manifested as impaired tubular resorption and necrosis of the proximal tubules at doses > or = 60 mg/kg/d. The no-observed-adverse-effect level (NOAEL) for the study was 30 mg/kg/d.     

Evaluation of subchronic inhalation toxicity of dimethyl disulfide in rats

This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.     

Evaluation of Subchronic Inhalation Toxicity of Dimethyl Disulfide in Rats

This study was carried out to investigate the potential subchronic inhalation toxicity of dimethyl disulfide (DMDS) via whole-body exposure in F344 rats. Groups of 10 rats of each sex were exposed to DMDS vapor by whole-body exposure at concentrations of 0, 5, 25, or 125 ppm for 6 h/day, 5 days/wk for 13 wk. All the rats were sacrificed at the end of treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were examined. At 25 ppm, a decrease in the body weight gain, food intake, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and blood urea nitrogen (BUN) was observed in the males, but not in the females. However, at 125 ppm, a decrease in the body weight gain, food intake, and thymus weight and an increase in the weights of adrenal glands were observed in both genders. Serum biochemical investigations revealed a decrease in the AST, ALT, BUN, creatine phosphokinase (CPK), and triglyceride levels and an increase in the glucose level. In contrast, no treatment-related effects were observed in the 5 ppm group. The toxic potency of DMDS was slightly higher in males than that in females. In these experimental conditions, the target organ was not determined in rats. The no-observed-adverse-effect concentration (NOAEC) was found to be 5 ppm, 6 h/day for male rats and 25 ppm, 6 h/day for female rats.     

28-Day inhalation toxicity of graphene nanoplatelets in Sprague-Dawley rats

Graphene, a two-dimensional engineered nanomaterial, is now being used in many applications, such as electronics, biological engineering, filtration, lightweight and strong nanocomposite materials, and energy storage. However, there is a lack of information on the potential health effects of graphene in humans based on inhalation, the primary engineered nanomaterial exposure pathway in workplaces. Thus, an inhalation toxicology study of graphene was conducted using a nose-only inhalation system for 28 days (6?h/day and 5 days/week) with male Sprague-Dawley rats that were then allowed to recover for 1-, 28-, and 90-day post-exposure period. Animals were separated into 4 groups (control, low, moderate, and high) with 15 male rats (5 rats per time point) in each group. The measured mass concentrations for the low, moderate, and high exposure groups were 0.12, 0.47, and 1.88?mg/m³, respectively, very close to target concentrations of 0.125, 0.5, and 2?mg/m³. Airborne graphene exposure was monitored using several real-time instrumentation over 10?nm to 20?μm for size distribution and number concentration. The total and respirable elemental carbon concentrations were also measured using filter sampling. Graphene in the air and biological media was traced using transmission electron microscopy. In addition to mortality and clinical observations, the body weights and food consumption were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for blood biochemical tests, and the organ weights were measured. No dose-dependent effects were recorded for the body weights, organ weights, bronchoalveolar lavage fluid inflammatory markers, and blood biochemical parameters at 1-day post-exposure and 28-day post-exposure. The inhaled graphenes were mostly ingested by macrophages. No distinct lung pathology was observed at the 1-, 28- and 90-day post-exposure. The inhaled graphene was translocated to lung lymph nodes. The results of this 28-day graphene inhalation study suggest low toxicity and a NOAEL of no less than 1.88?mg/m³.     

DIESEL EXHAUST AFFECTS THE ABNORMAL DELIVERY IN PREGNANT MICE AND THE GROWTH OF THEIR YOUNG

To clarify the toxic effects of diesel exhaust (DE) on delivery in mice and on growth of young, C57Bl-strain females were exposed to 0.3, 1.0, or 3.0 mg diesel exhaust particles (DEP)/m 3 or filtered clean air (control) for 4 mo (12 h/day, 7 days/wk). After exposure, some females from each group were examined by necropsy, and the remainders were mated with unexposed males. Estrous females for necropsy who had been exposed to 1.0 mg DEP/m 3 had significantly lower uterine weights than the control estrous females. In the mated females, 9.1, 10.0, or 25.0% (0.3, 1.0, or 3.0 mg DEP/m 3) of the pregnancies resulted in abnormal deliveries (abortion and unable delivery), but this was not significant. The rate of good nest construction by delivered females exposed to 3.0 mg DEP/m 3 was significantly lower. Young were weighed at 11, 14, and 21 days, and weekly from wk 4 to 9 after birth. Body weights of male young of dams exposed to 1.0 or 3.0 mg DEP/m 3 were significantly lower at 6 and 8 wk of age. Body weights of female young of dams exposed to 1.0 or 3.0 mg DEP/m 3 were also significantly lower at 6, 8, and 9 wk. Vaginal orifices of young female mice whose dams were exposed to 0.3 and 1.0 mg DEP/m 3 opened significantly earlier. The young were killed at 30 or 70 days during deep anesthesia, and their body weights, organ weights, and body lengths were measured. Anogenital distance (AGD) of 30-day-old males whose dams were exposed to 0.3 mg DEP/m 3 was significantly shorter than that of the controls. Weights of thymus and ovary in 30-day-old females whose dams were exposed to 3.0 mg DEP/m 3 were significantly lower. In 70-day-old males of dams exposed to 3.0 mg DEP/m 3, body weights were significantly lower and AGD was significantly shorter. Weights of adrenals, testes, and seminal vesicles in 70-day-old males with dams exposed to 1.0 mg DEP/m 3 were significantly lower. In 70-day-old females with dams exposed to DE, body weights in the 3.0-mg DEP/m 3 group were significantly lower, and weights of adrenals, liver, and thymus in the 1.0-mg DEP/m 3 group were significantly lower. Thymus weights in 70-day-old females with dams exposed to 0.3 mg DEP/m 3 were significantly lower. Crown-rump length (CR) in 70-day-old females with dams exposed to 1.0 or 3.0 mg DEP/m 3 was significantly shorter. These results show that toxic substances in DE might cause abnormal delivery in mice, and that exposed females affected the growth and sexual maturation of their young.