Subchronic toxicity of cyclohexane in rats and mice by inhalation exposure

Inhalation studies were conducted to determine the potential toxicity and/or potential neurotoxicity of cyclohexane. Groups of rats and mice were exposed to 0, 500, 2000, or 7000 ppm concentrations of cyclohexane vapor 6 hr/day, 5 days/week for 14 weeks. Subgroups of rats and mice were further observed during a 1-month recovery period. Functional observational battery (FOB) and motor activity (MA) behavioral tests were conducted on rats. These tests were conducted prior to the exposure series and during weeks 4, 8, and 13 on non-exposure days. Clinical pathology evaluations were conducted after approximately 7, 13, and 18 weeks. Approximately 14 and 18 weeks after study initiation, tissues from rats and mice were histologically processed and evaluated by light microscopy. During exposure to 2000 or 7000 ppm, rats and mice had a diminished response or an absent response to delivery of a punctate auditory alerting stimulus. Immediately following removal of rats from the inhalation chambers, 7000 ppm males and females and 2000 ppm females displayed a compound-related increase in the incidence of wet and/or stained fur (which occurred in the areas of the mouth, chin, and/or perineum). These signs were transient, were not observed during exposure or prior to exposure the following day, and were not associated with any behavioral or morphological changes. During exposure sessions, mice exposed to 7000 ppm exhibited clinical signs of toxicity which included hyperactivity, circling, jumping/hopping, excessive grooming, kicking of rear legs, standing on front legs, and occasional flipping behavior. Clinical signs of toxicity observed in 7000 ppm mice immediately after exposure included hyperactivity, hyperreactivity, ruffled fur (females only), gait abnormalities, spasms in both rear legs, and excessive grooming (males only). The clinical signs observed in mice during and immediately after exposure were transient, and were not present prior to the subsequent exposure. A few mice exposed to 2000 ppm appeared hyperactive during exposure in the latter portion of the study. There were no compound-related changes in mean body weights, body weight gains, food consumption, food efficiency, or mortality; and there were no ophthalmological abnormalities in rats or mice. In addition, there were no compound-related effects on 37 different behavioral parameters assessed during the FOB or during motor activity tests in rats. Male and female mice exposed to 7000 ppm had slight increases in measures of circulating erythrocyte mass (red blood cells, hemoglobin, hematocrit) and plasma protein concentration (males only). Male rats and male and female mice exposed to 7000 ppm had significantly increased relative liver weights, and 7000 ppm male mice also had significantly increased absolute liver weights at the end of the exposure period. At the end of the 1-month recovery period, absolute and relative liver weights of male and female mice were similar to control. However, relative liver weights of 7000 ppm male rats continued to be significantly higher at the end of the recovery period. Male and female rats exposed to 7000 ppm had a significantly increased incidence of hepatic centrilobular hypertrophy at the end of the exposure period, which was not observed at the conclusion of the 1-month recovery period. No microscopic changes were observed in mice. In rats, the no-observed-effect level (NOEL) for acute, transient effects was 500 ppm based on a diminished/absent response to an auditory alerting stimulus at 2000 ppm and above. The NOEL for subchronic toxicity in rats was 7000 ppm based on the lack of adverse effects on body weight, clinical chemistry, tissue morphology, and neurobehavioral parameters. In mice, the NOEL for acute, transient effects was 500 ppm based on behavioral changes during exposure at 2000 ppm and above. The NOEL for subchronic toxicity in mice is 2000 ppm based on hematological changes at 7000 ppm.     

SUBCHRONIC TOXICITY OF CYCLOHEXANE IN RATS AND MICE BY INHALATION EXPOSURE

Inhalation studies were conducted to determine the potential toxicity and/or potential neurotoxicity of cyclohexane. Groups of rats and mice were exposed to 0, 500, 2000, or 7000 ppm concentrations of cyclohexane vapor 6 hr/day, 5 days/week for 14 weeks. Subgroups of rats and mice were further observed during a 1-month recovery period. Functional observational battery (FOB) and motor activity (MA) behavioral tests were conducted on rats. These tests were conducted prior to the exposure series and during weeks 4, 8, and 13 on non-exposure days. Clinical pathology evaluations were conducted after approximately 7, 13, and 18 weeks. Approximately 14 and 18 weeks after study initiation, tissues from rats and mice were histologically processed and evaluated by light microscopy.

During exposure to 2000 or 7000 ppm, rats and mice had a diminished response or an absent response to delivery of a punctate auditory alerting stimulus. Immediately following removal of rats from the inhalation chambers, 7000 ppm males and females and 2000 ppm females displayed a compound-related increase in the incidence of wet and/or stained fur (which occurred in the areas of the mouth, chin, and/or perineum). These signs were transient, were not observed during exposure or prior to exposure the following day, and were not associated with any behavioral or morphological changes. During exposure sessions, mice exposed to 7000 ppm exhibited clinical signs of toxicity which included hyperactivity, circling, jumping/hopping, excessive grooming, kicking of rear legs, standing on front legs, and occasional flipping behavior. Clinical signs of toxicity observed in 7000 ppm mice immediately after exposure included hyperactivity, hyperreactivity, ruffled fur (females only), gait abnormalities, spasms in both rear legs, and excessive grooming (males only). The clinical signs observed in mice during and immediately after exposure were transient, and were not present prior to the subsequent exposure. A few mice exposed to 2000 ppm appeared hyperactive during exposure in the latter portion of the study. There were no compound-related changes in mean body weights, body weight gains, food consumption, food efficiency, or mortality; and there were no ophthalmological abnormalities in rats or mice. In addition, there were no compound-related effects on 37 different behavioral parameters assessed during the FOB or during motor activity tests in rats.

Male and female mice exposed to 7000 ppm had slight increases in measures of circulating erythrocyte mass (red blood cells, hemoglobin, hematocrit) and plasma protein concentration (males only).

Male rats and male and female mice exposed to 7000 ppm had significantly increased relative liver weights, and 7000 ppm male mice also had significantly increased absolute liver weights at the end of the exposure period. At the end of the 1-month recovery period, absolute and relative liver weights of male and female mice were similar to control. However, relative liver weights of 7000 ppm male rats continued to be significantly higher at the end of the recovery period. Male and female rats exposed to 7000 ppm had a significantly increased incidence of hepatic centrilobular hypertrophy at the end of the exposure period, which was not observed at the conclusion of the 1-month recovery period. No microscopic changes were observed in mice.

In rats, the no-observed-effect level (NOEL) for acute, transient effects was 500 ppm based on a diminished/absent response to an auditory alerting stimulus at 2000 ppm and above. The NOEL for subchronic toxicity in rats was 7000 ppm based on the lack of adverse effects on body weight, clinical chemistry, tissue morphology, and neurobehavioral parameters. In mice, the NOEL for acute, transient effects was 500 ppm based on behavioral changes during exposure at 2000 ppm and above. The NOEL for subchronic toxicity in mice is 2000 ppm based on hematological changes at 7000 ppm.     

Acute and subchronic neurotoxicological evaluation of tetrahydrofuran by inhalation in rats.

Groups of adult male and female rats received exposure to tetrahydrofuran (THF) vapor by inhalation in acute or subchronic exposure scenarios. Acute exposure concentrations were 0, 500, 2500, or 5000 ppm for 6 hr. Evaluations conducted immediately after exposure included clinical observations, motor activity assessments (MA), and a battery of functional tests (FOB) designed to reveal nervous system dysfunction. During exposure to 2500 and 5000 ppm, rats had a diminished or absent startle response to a punctate auditory alerting stimulus. Following exposure to 5000 ppm, male and female rats were lethargic, exhibited abnormal gait or mobility, and splayed rear feet. Lethargy and splayed rear feet were also observed in females exposed to 2500 ppm. During the subsequent FOB, males exposed to 5000 ppm had a lower incidence of palpebral closure, higher incidences of slow or absent righting reflex, and a biphasic pattern of reduced motor activity followed by increased motor activity. Females exposed to 5000 ppm had increased incidences of palpebral closure in the open field, increased incidences of slow or absent righting reflex, and decreased motor activity. During the 14-week subchronic exposure series, daily THF exposure concentrations were 0, 500, 1500, or 3000 ppm, and neurobehavioral evaluations occurred on non-exposure days at approximately monthly intervals. Diminished startle responses to an auditory alerting stimulus were observed during exposure to 1500 or 3000 ppm; however, repeated exposures did not cause additional neurobehavioral or pathological effects. This pattern of effects is suggestive of transient sedation. Despite daily reinstatement of acute sedative effects during repeated exposure with up to 3000 ppm, THF did not produce any persistent or cumulative effects on nervous system structure or function. The demonstrated no-observed-effect level of THF for both acute and subchronic exposure was 500 ppm.     

Inhalation toxicity and genotoxicity of hydrochlorofluorocarbon (HCFC)-225ca and HCFC-225cb

The acute, subchronic and genetic toxicity of the hydrochlorofluorocarbons HCFC-225ca and HCFC-225cb were evaluated to assist in establishing proper handling guides. In acute inhalation studies, rats were exposed for 4 h to various concentrations of each isomer. Based on the mortality incidence, the LC50 value for HCFC-225cb for males and females (combined) was 36800 ppm. For HCFC-225ca, the LC50 for males and females (combined) was 37300 ppm. Narcotic-like effects, e.g. prostration, incoordination and reduced motor activity, were observed during exposure to either isomer, but these signs were not evident 15 min after termination of exposure. Histopathological examination of the liver revealed an increase in mitotic figures with vacuolation of hepatocytes and fluid-filled, congested hepatic sinusoids. In cardiac sensitization studies, HCFC-225cb induced a cardiac sensitization response at 20000 ppm, with one fatal response, whereas a blend of the two isomers (45% HCFC-225ca/55% HCFC-225cb) produced a cardiac sensitization response at 15000 ppm. In 4-week subchronic inhalation studies, male and female rats were whole-body exposed to HCFC-225cb at concentrations of 0, 1000, 5000 or 15000 ppm for 6 h a day, 5 days per week. Similarly, male and female rats were whole-body exposed to HCFC-225ca concentrations of 0, 50, 500 or 5000 ppm for 6 h a day, 5 days per week. During exposure, narcotic-like and irritant effects were observed. A dose-related decrease in cholesterol and triglycerides was observed in the treated rats, with males being affected more than females. Increases in liver weight were observed in most male and female rats exposed to either isomer. The increase in liver weight was consistent in male rats with microscopic evidence of hepatocyte hypertrophy. Although liver weight was increased in female rats, no hepatocyte enlargement was observed in treated female rats. Increases in cytochrome P-450 and beta-oxidation activities were also observed in male and female rats exposed to either isomer. Neither of the HCFC-225 isomers was mutagenic in the Ames reverse mutation assay, or clastogenic in the chromosomal aberration assay with Chinese hamster lung cells. Also, neither isomer induced unscheduled DNA synthesis in liver cells. However, both isomers were clastogenic in the chromosomal aberration assay with human lymphocytes in the absence of S-9. No increases in aberrant cells were observed in activated cells exposed to either isomer.     

ACUTE AND SUBCHRONIC NEUROTOXICOLOGICAL EVALUATION OF TETRAHYDROFURAN BY INHALATION IN RATS

Groups of adult male and female rats received exposure to tetrahydrofuran (THF) vapor by inhalation in acute or subchronic exposure scenarios. Acute exposure concentrations were 0, 500, 2500, or 5000 ppm for 6 hr. Evaluations conducted immediately after exposure included clinical observations, motor activity assessments (MA), and a battery of functional tests (FOB) designed to reveal nervous system dysfunction. During exposure to 2500 and 5000 ppm, rats had a diminished or absent startle response to a punctate auditory alerting stimulus. Following exposure to 5000 ppm, male and female rats were lethargic, exhibited abnormal gait or mobility, and splayed rear feet. Lethargy and splayed rear feet were also observed in females esposed to 2500 ppm. During the subsequent FOB, males exposed to 5000 ppm had a lower incidence of palpebral closure, higher incidences of slow or absent righting reflex, and a biphasic pattern of reduced motor activity followed by increased motor activity. Females exposed to 5000 ppm had increased incidences of palpebral closure in the open field, increased incidences of slow or absent righting reflex, and decreased motor activity.

During the 14-week subchronic exposure series, daily THF exposure concentrations were 0, 500, 1500, or 3000 ppm, and neurobehavioral evaluations occurred on non-exposure days at approximately monthly intervals. Diminished startle responses to an auditory alerting stimulus were observed during exposure to 1500 or 3000 ppm; however, repeated exposures did not cause additional neurobehavioral or pathological effects. This pattern of effects is suggestive of transient sedation. Despite daily reinstatement of acute sedative effects during repeated exposure with up to 3000 ppm, THF did not produce any persistent or cumulative effects on nervous system structure or function. The demonstrated no-observed-effect level of THF for both acute and subchronic exposure was 500 ppm.     

Toxicology and carcinogenesis studies of 1-bromopropane (CAS No. 106-94-5) in F344/N rats and B6C3F1 mice (inhalation studies)

In the early to mid 1990s, 1-bromopropane was used primarily as an intermediate in the production of pesticides, quaternary ammonium compounds, flavors and fragrances, pharmaceuticals, and other chemicals in well-controlled, closed processes. In the mid to late 1990s, it was introduced as a less toxic replacement for methylene chloride in emissive applications such as vapor and immersion degreasing operations and critical cleaning of electronics and metals. 1-Bromopropane was also introduced as a nonflammable, nontoxic, fast-drying, and inexpensive solvent for adhesive resins, and has been marketed as a replacement for ozone depleting refrigerants. 1-Bromopropane was nominated for study by the Occupational Safety and Health Administration based on the potential for widespread occupational and environmental exposure and a lack of toxicity and carcinogenicity data. Male and female F344/N rats and B6C3F1 mice were exposed to 1-bromopropane (99% or greater pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli and mouse peripheral blood. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, 500, 1,000, or 2,000 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study except one 500 ppm male. Mean body weights of 2,000 ppm rats were significantly less than those of the chamber controls. The absolute kidney weight of 1,000 ppm males, relative kidney weights of all exposed groups of males, and absolute and relative kidney weights of all exposed groups of females were significantly increased. The absolute and relative liver weights of 1,000 ppm males, relative liver weights of 500 and 2,000 ppm males, and absolute and relative liver weights of 500 ppm or greater females were significantly increased. Nasal lesions included suppurative inflammation in males exposed to 500 ppm or greater, respiratory epithelial necrosis in 1,000 and 2,000 ppm males, and respiratory epithelial regeneration in 1,000 and 2,000 ppm females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, 500, 1,000, or 2,000 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. All 2,000 ppm males, two 2,000 ppm females, four 500 ppm males, one 1,000 ppm male, and one 1,000 ppm female died early. The mean body weight gain of 1,000 ppm males was significantly less than that of the chamber controls. Abnormal breathing, lethargy, and eye discharge were observed primarily during week 1 in groups exposed to 500 ppm or greater. Liver weights of 1,000 ppm males and of females exposed to 500 ppm or greater were significantly increased. Kidney weights of 1,000 and 2,000 ppm females were significantly increased. Microscopic lesions related to 1-bromopropane exposure occurred in the lung, liver, and nose of males and females and were primarily seen in mice exposed to 500 ppm or greater. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, 250, 500, or 1,000 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were exposed to the same concentrations for 23 days. All rats survived to the end of the study. Mean body weights of 1,000 ppm males were significantly less than those of the chamber controls. The increases in sorbitol dehydrogenase activities in 500 ppm males and 1,000 ppm males and females were consistent with the histopathologic evidence of mild hepatotoxicity caused by 1-bromopropane. Liver weights of males exposed to 250 ppm or greater and of females exposed to 125 ppm or greater were significantly increased. Spleen and kidney weights of 1,000 ppm females were significantly increased. Exposure concentration-related decreases of 28% in sperm motility and 37% in sperm counts were seen in the 1,000 ppm group of male rats. Female rats in all three exposure groups evaluated exhibited altered estrous cycles, spending significantly more time in extended estrus and less time in extended diestrus. The incidences of cytoplasmic vacuolization of the liver were significantly increased in males exposed to 250 ppm or greater and in females exposed to 500 ppm or greater. Hepatocyte degeneration was also observed in 1,000 ppm females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 14 weeks. One 250 ppm male and four males and five females in the 500 ppm groups died early. Mean body weights of exposed groups were similar to those of the chamber controls. Lethargy was observed in males and females exposed to 500 ppm, and abnormal breathing was observed in moribund mice. The kidney, liver, and lung weights of 500 ppm females were significantly greater than those of the chamber controls. The kidney weights of 500 ppm males were significantly decreased. Sperm counts in the 500 ppm group of male mice were 28% less than that in the chamber controls. Female mice exhibited altered estrous cycles, with females in the 500 ppm group spending significantly more time in extended diestrus and those in the 250 ppm group spending significantly more time in extended estrus compared to the chamber controls. Nonneoplastic lesions were observed in the nose, larynx, trachea, lung, and liver of 500 ppm males and females and in the adrenal cortex of 500 ppm females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, or 500 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 105 weeks. Survival of 500 ppm males was significantly less than that of the chamber control group. Mean body weights of exposed groups were similar to those of the chamber controls. Increased incidences of macroscopic, soft, pale-yellow to green, variably sized nodules were seen predominantly in the nose and skin of exposed rats. The number of animals with multiple masses was increased in the 500 ppm groups. In most cases, these lesions were microscopically shown to be suppurative inflammation, many with Splendore-Hoeppli material. The incidence of adenoma of the large intestine (colon or rectum) was significantly greater in 500 ppm females than in the chamber control group. The incidence of adenoma of the large intestine in 250 ppm males exceeded the historical control ranges for inhalation studies and all routes. The incidences of keratoacanthoma, basal cell adenoma, basal cell carcinoma, or squamous cell carcinoma (combined) were significantly greater in all exposed groups of males than in the chamber control group and exceeded the historical control range for inhalation studies. The incidences of keratoacanthoma and of keratoacanthoma or squamous cell carcinoma (combined) in 250 and 500 ppm males were also significantly increased and exceeded the historical control ranges for inhalation studies. In 500 ppm females, the incidence of squamous cell papilloma, keratoacanthoma, basal cell adenoma, or basal cell carcinoma (combined) exceeded the historical control range for inhalation studies. The incidence of malignant mesothelioma was significantly greater in 500 ppm males than in the chamber control group. The incidences of pancreatic islet adenoma in all exposed groups of males and of pancreatic islet adenoma or carcinoma (combined) in 125 and 250 ppm males were significantly increased. Treatment-related nonneoplastic lesions were observed in the respiratory system of exposed male and female rats. In the nose, the incidences of suppurative chronic inflammation, chronic active inflammation, glandular hyperplasia, respiratory epithelial hyperplasia (females), and respiratory metaplasia of the olfactory epithelium (females) were increased in all exposed groups. In the larynx, the incidences of chronic active inflammation and squamous metaplasia (except 125 ppm females) were increased in all exposed groups, and the incidences of suppurative chronic inflammation were increased in the 500 ppm groups. Also, chronic inflammation of the lung was observed in the 500 ppm females. In the trachea, there were increased incidences of chronic active inflammation in all exposed groups of females and 500 ppm males, and the incidence of epithelial hyperplasia was increased in 500 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, or 250 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups was similar to that of the chamber controls. Mean body weights of all exposed groups were similar to those of the chamber controls throughout the study. In the females, there were increased incidences of alveolar/bronchiolar adenoma, alveolar/bronchiolar carcinoma, and alveolar/bronchiolar adenoma or carcinoma (combined); the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were significantly increased in all exposed groups of females. There were significantly increased incidences of cytoplasmic vacuolization of the bronchiolar epithelium in all exposed male groups and regeneration of the bronchiolar epithelium in all exposed groups of males and females. In the nose, there were significantly increased incidences of cytoplasmic vacuolization of the respiratory epithelium in all exposed groups of males and in 125 and 250 ppm females. There were significantly increased incidences of respiratory epithelial hyperplasia in all exposed female groups and in 62.5 and 250 ppm males. (ABSTRACT TRUNCATED)     

Toxicology and carcinogenesis studies of diethylamine (CAS No. 109-89-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Diethylamine is used mainly as a chemical intermediate to produce the corrosion inhibitor N,N-diethylethanolamine and a lesser amount is used to produce pesticides and insect repellants and in rubber processing. Diethylamine was nominated for study by the National Institute of Environmental Health Sciences based upon its high production volume and ubiquitous natural occurrence in trace amounts and because of the lack of chronic toxicity and carcinogenicity data on the chemical. Male and female F344/N rats and B6C3F1 mice were exposed to diethylamine (approximately 99.9% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in bacterial mutagenicity tester strains and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study. The mean body weights of 250 and 500 ppm males and females and 125 ppm males were significantly less than those of the chamber controls. Clinical findings included lethargy, nasal/eye discharge, abnormal breathing, thinness, eye abnormalities, and discolored urine. The thymus weights of males exposed to 125 ppm or greater and females exposed to 500 ppm were significantly less than those of the chamber controls. Focal eye lesions were noted at necropsy in four males and three females exposed to 500 ppm and one male exposed to 250 ppm. Crusty noses were observed in most 500 ppm males and females and in two 250 ppm males. Suppurative inflammation, necrosis of the turbinates (except in one 125 ppm female), and squamous metaplasia of the respiratory epithelium of the nose were present in all rats exposed to 125 ppm or greater. Ulcer of the respiratory epithelium and atrophy of the olfactory epithelium occurred in all rats exposed to 250 or 500 ppm, and ulcer of the nasopharyngeal duct was present in all 500 ppm rats. Suppurative inflammation of the cornea was present in most rats exposed to 500 ppm. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. Two males and three females exposed to 500 ppm died during the first week of the study. The mean body weights of males and females exposed to 125 ppm or greater were significantly less than those of the chamber controls. Males and females exposed to 250 or 500 ppm lost weight during the study. Lethargy, abnormal breathing, and thinness were observed in most mice exposed to 250 or 500 ppm. Eye irritation and discharge, nasal discharge, and low fecal and urine output were noted in 500 ppm mice. Thymus weights of 250 and 500 ppm males and 125 ppm or greater females were significantly less than those of the chamber controls. Suppurative inflammation of the nose occurred in all males exposed to 250 or 500 ppm and all females exposed to 125 ppm or greater, and most males exposed to 125 ppm. Turbinate necrosis occurred in all exposed mice except one 31 ppm female. Squamous metaplasia of the respiratory epithelium and olfactory epithelial atrophy were seen in mice exposed to 125 ppm or greater. In the lung, the incidence of minimal chronic active inflammation of mainstem bronchi was significantly increased in 500 ppm males. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. There were significant exposure concentration-related decreases in sperm motility in 32, 62, and 125 ppm males; there were no significant differences in the lengths of estrous cycles between chamber control and exposed groups of females. Exposure-related nasal lesions were seen primarily in rats exposed to 62 or 125 ppm. These lesions included turbinate necrosis, suppurative inflammation, respiratory epithelial hyperplasia, squamous metaplasia of the respiratory epithelium, and olfactory epithelial atrophy. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. The mean body weights of 125 ppm males and females were significantly less than those of the chamber controls. There were significant exposure concentration-related decreases in sperm motility in males exposed to 32, 62, or 125 ppm; the estrous cycle of 125 ppm females was significantly longer than that of the chamber controls but only by half a day. Histopathologic changes were noted primarily in the nasal cavity and involved both the respiratory and olfactory epithelium of males and females principally in the 62 or 125 ppm groups. These lesions included suppurative inflammation, squamous metaplasia of the respiratory epithelium, olfactory epithelial atrophy, and necrosis of the turbinates. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, or 125 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of rats was similar to that of the chamber control groups. Mean body weights of males and females exposed to 125 ppm were less than those of the chamber controls after week 57. Increased incidences of eye abnormality occurred in exposed males and females. A spectrum of nonneoplastic lesions was observed in the respiratory and olfactory epithelium of the nose in exposed rats. The lesions included suppurative inflammation, ulceration of the respiratory epithelium, hyaline droplet accumulation in the glands of the respiratory epithelium, necrosis of the turbinates, squamous metaplasia of the respiratory epithelium, hyperplasia of the respiratory epithelium, atrophy of the olfactory epithelium, hyaline droplet accumulation in the respiratory and olfactory epithelium, basal cell hyperplasia of the olfactory epithelium, respiratory metaplasia of the olfactory epithelium, and goblet cell hyperplasia. The incidence of chronic inflammation of the pleura was significantly increased in 125 ppm females. The incidences of histiocytic cellular infiltration of the alveolus of the lung were significantly increased in all exposed groups of females and the incidence of chronic inflammation was significantly increased in 125 ppm females. In 125 ppm males, the incidence of suppurative inflammation of the cornea was significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to diethylamine vapor at concentrations of 0, 16, 31, or 62.5 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of mice was similar to that of the chamber control groups. Mean body weights of males and females were similar to those of the chamber controls. Eye abnormality was observed in greater incidence in exposed groups of males than in the chamber controls, and torso/ventral ulcer/abscess was observed in six 62.5 ppm males compared to none in the chamber controls. A similar spectrum of nonneoplastic lesions was seen in the nose of exposed mice as was seen in rats. GENETIC TOXICOLOGY: Diethylamine was not mutagenic in either of two independent bacterial mutagenicity assays, each conducted with and without exogenous metabolic activation enzymes. Bacterial strains tested included Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 and Escherichia coli strain WP2 uvrA/pKM101. In addition to the negative results in the two bacterial assays, no significant increases in the frequencies of micronucleated erythrocytes were seen in peripheral blood of male or female B6C3F1 mice from the 3-month study. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was no evidence of carcinogenic activity of diethylamine in male or female F344/N rats exposed to 31, 62.5, or 125 ppm. There was no evidence of carcinogenic activity of diethylamine in male or female B6C3F1 mice exposed to 16, 31, or 62.5 ppm. Exposure to diethylamine resulted in increased incidences of nonneoplastic lesions of the nose in male and female rats and mice, of the cornea in male rats, and of the pleura and lung in female rats.     

Influences of gender,development, pregnancy and ethanol consumption on the hematotoxicity of inhaled 10 ppm benzene

 The hematotoxic effects of benzene in both humans and animals are well documented. Current estimates concerning the risks associated with benzene exposure are usually based on adult, male cohort studies; however, there are indications that females may respond differently than males to benzene and that fetuses may respond differently than adults. Another factor to be considered in risk estimates is the impact of personal habits. In experimental animals, ethanol consumption is known to increase the hematotoxicity of benzene; therefore, alcohol consumption may also alter the potential risk of individuals exposed to benzene. To address some of the factors that may confound risk estimates for benzene exposure, a series of experiments were performed. Age-matched male as well as pregnant and virgin female Swiss Webster mice were exposed to 10 ppm benzene for 6 h a day over 10 consecutive days (days 6 through 15 of gestation for the pregnant females). Half of the animals also received 5% ethanol in the drinking water during this period. On day 11, bone marrow cells from the adults and liver cells from the fetuses were assayed for the numbers of erythroid colony-forming units (CFU-e). CFU-e assays were also performed on bone marrow cells isolated from 6-week postpartum dams exposed during gestation and from in utero-exposed 6-week old males and females. Gender differences were clearly observed in the responses to the various exposure protocols. Depressions in CFU-e numbers were only seen in male mice while elevations in CFU-e numbers were only seen in female mice. Male mice exposed as adults for 10 days to benzene (B), ethanol (E) or benzene+ethanol (B+E) exhibited depressed CFU-e levels as did male fetal mice exposed to B in utero. In addition, adult male mice which had been exposed in utero to either B or to E individually displayed depressed CFU-e levels. In contrast, none of the groups of female mice exhibited any depressions in CFU-e numbers after any of the exposures. Elevations in CFU-e numbers were observed among pregnant females exposed to E and among adult females exposed to B+E in utero. In summary, a majority (6/9) of the exposure protocols produced depressions in the CFU-e numbers of male mice, whereas a majority (7/9) of the exposure protocols produced no changes in the CFU-e numbers of female mice. Those changes that were observed in females consisted of elevations of CFU-e numbers. These results suggest that the male erythron is more susceptible than the female erythron to the hematotoxicants benzene and ethanol, regardless of whether exposures occur in utero or during adulthood. Received: 21 February 1995 / Accepted: 14 May 1995     

Toxicology and carcinogenesis studies of propargyl alcohol (CAS No. 107-19-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Propargyl alcohol is a commercially available acetylenic primary alcohol. It is also a by-product in the industrial synthesis of butynediol from acetylene and formaldehyde with copper acetylide as catalyst. Propargyl alcohol is used as a reactant/chemical intermediate, pharmaceutical intermediate, agricultural chemical intermediate, soil fumigant, corrosion inhibitor, solvent stabilizer, and polymer modifier. It has also been used to prevent the hydrogen embrittlement of steel. Propargyl alcohol was nominated by the National Cancer Institute for study because of the potential for human exposure in occupational settings through inhalation and dermal contact. Male and female F344/N rats and B6C3F1 mice were exposed to propargyl alcohol (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 propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90 )(12 minutes) per day, 5 days per week for 16 days. All males exposed to 125 ppm or greater and all females exposed to 250 or 500 ppm died by the end of day 3 of the study, and one 125 ppm female died on day 5. Mean body weights were significantly decreased in 62.5 ppm males and 125 ppm females. Clinical findings in the 125 and 250 ppm groups included lethargy, ataxia, abnormal breathing, and nasal/eye discharge. Right kidney weights of 62.5 and 125 ppm females and liver weights of 125 ppm females were significantly greater than those of the chamber controls. All 250 and 500 ppm males and females had moderate to marked periportal necrosis, congestion, and erythrophagocytosis of the liver. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 17 days. All mice exposed to 125 ppm or greater died by day 3 of the study. Mean body weights of mice exposed to 62.5 ppm were significantly less than those of the chamber controls. Clinical findings in the 62.5 and/or 125 ppm groups included abnormal breathing, nasal/eye discharge, thinness, and lethargy. Right kidney weights of 31.3 ppm mice were significantly greater, and thymus weights of 62.5 ppm males were significantly less than those of the chamber controls. The livers of all males and females exposed to 250 or 500 ppm exhibited marked periportal necrosis, congestion, and erythrophagocytosis; these lesions also occurred in all 125 ppm males with less severity. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. The incidences of minimal to mild hyperplasia of respiratory epithelium of the nose were significantly increased in all exposed groups except 8 ppm males and 4 ppm females. Squamous metaplasia of the respiratory epithelium was noted in a few males and most females exposed to 64 ppm. Necrosis of olfactory epithelium was present in half of the males and females exposed to 64 ppm and in a few males and females exposed to 32 ppm. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 8 ppm or greater and 32 and 64 ppm females were significantly less than those of the chamber control groups. Histopathologic changes occurred in the nasal cavity of mice and involved both the respiratory and olfactory epithelium in groups exposed to 16 ppm or greater. Lesions included minimal to moderate suppurative inflammation, minimal to moderate squamous metaplasia of the respiratory epithelium, minimal to mild hyaline degeneration (accumulation) in the respiratory epithelium, minimal to moderate olfactory epithelial atrophy, minimal to moderate hyperplasia of glands in the olfactory region, minimal necrosis of olfactory epithelium, and minimal to moderate turbinate atrophy. There were no biologically significant differences in organ weights between exposed and chamber control groups. Reproductive tissue parameters of exposed males were similar to those of the chamber controls. Only 2/9 female mice in the 64 ppm group exhibited regular estrous cyclicity compared to 6/10 in the controls. Females exposed to 16 ppm differed from chamber controls in the relative time in the estrous stages, and 64 ppm females had a significantly increased probability of extended estrus. No gross lesions were observed at necropsy. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 16, 32, or 64 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of 32 and 64 ppm males was significantly less than that of the chamber control group. Mean body weights of males exposed to 64 ppm were less than those of the chamber controls after week 24 of the study. Nasal respiratory epithelial adenomas were present in three 64 ppm males and one 32 ppm female; the incidence in 64 ppm males exceeded the historical control ranges. A spectrum of nonneoplastic lesions occurred in the respiratory and olfactory epithelium of rats at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and olfactory basal cell hyperplasia were significantly increased in all exposed groups of rats. The incidences of lesions of the olfactory epithelium including hyperplasia, glandular hyperplasia, atrophy, respiratory metaplasia, degeneration, necrosis, hyaline droplet accumulation, and chronic active inflammation were significantly increased in one or more exposed groups of males and/or females. The incidence of mononuclear cell leukemia was significantly increased in males exposed to 64 ppm, and the incidence exceeded the historical control ranges. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 8, 16, or 32 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups was similar to that of the chamber control groups. Mean body weights of 16 and 32 ppm females were less than those of the chamber control group after weeks 73 and 21, respectively. Eye abnormality (unspecified) was observed after one full year of exposure with the incidence increasing in an exposure concentration-related manner. The incidences of nasal respiratory epithelial adenoma increased with a positive trend and were significantly increased in groups exposed to 32 ppm. A spectrum of nonneoplastic lesions occurred in the nasal respiratory and olfactory epithelium of mice at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and squamous metaplasia were significantly increased in most exposed groups of mice. Suppurative inflammation was often associated with the squamous metaplasia, and turbinate atrophy was present in all exposed mice (except one 16 ppm male). The incidences of olfactory epithelial atrophy and respiratory metaplasia were increased in the 16 and 32 ppm groups. Significantly increased incidences of Harderian gland adenoma occurred in 8 and 32 ppm males. GENETIC TOXICOLOGY: Propargyl alcohol was mutagenic in Salmonella typhimurium strain TA100 in the absence of liver S9 activation enzymes only; no mutagenicity was observed in TA100 in the presence of S9 enzymes, in TA1535 without S9, or in TA98 with or without S9. In vivo, no significant increases in the frequencies of micronucleated normochromatic erythrocytes were observed in peripheral blood samples from male mice exposed by inhalation to propargyl alcohol for 3 months. In female mice, propargyl alcohol exposure produced a small increase in micronucleated erythrocytes that was judged to be equivocal. No significant changes in the percentage of polychromatic erythrocytes were seen in either male or female mice after 3 months of exposure to propargyl alcohol. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenetic activity of propargyl alcohol in male F344/N rats based on increased incidences of nasal respiratory epithelial adenoma and mononuclear cell leukemia. There was no evidence of carcinogenic activity of propargyl alcohol in female F344/N rats exposed to 16, 32, or 64 ppm. There was some evidence of carcinogenic activity of propargyl alcohol in male and female B6C3F1 mice based on increased incidences of nasal respiratory epithelial adenoma. The increased incidences of Harderian gland adenoma in male B6C3F1 mice may have been related to exposure to propargyl alcohol. Exposure to propargyl alcohol resulted in increased incidences of nonneoplastic nasal lesions in male and female rats and mice. Synonyms: Ethynylcarbinol; 1-hydroxy-2-propyne; 3-hydroxy-1-propyne; PA; 1-propyn-3-ol; 1-propyn-3-yl alcohol; 2-propynol; 3-propynol; propynyl alcohol; 2-propynyl alcohol.     

Developmental and reproductive toxicity evaluation of toluene vapor in the rat. I. Reproductive toxicity

The reproductive toxicity of toluene was evaluated in a 2-generation test in which male and female Sprague–Dawley rats, parental (F0) and first generation (F1), were exposed to toluene via whole body inhalation, 6 h/day, 7 days/week for 80 days premating and 15 days of mating at concentrations of 0, 100, 500 and 2000 ppm (0, 375, 1875 and 7500 mg/m³). Toluene was administered at 2000 ppm to both sexes, or to females or males only to be mated with untreated partners. Pregnant females at all dose levels were exposed from gestation day (GD) 1–20 and lactation day (LD) 5–21. At LD5, females were removed from their litters for daily exposure and returned when 6 h of exposure was completed. F1 pups selected to produce the F2 generation were treated for 80 days beginning immediately after weaning (LD21) and initially mated at a minimum of 100 days of age. F2 pups were not exposed to toluene by inhalation.

Toluene exposure did not induce adverse effects on fertility, reproductive performance, or maternal/pup behaviors during the lactation period in males and females of the parental or first generation, but did inhibit growth in F1 and F2 offspring in the 2000 ppm (both sexes treated) and 2000 ppm (females only treated) groups. Caesarean section of selected 2000 ppm (both sexes treated) dams at GD20 showed reduced fetal body weight and skeletal variations. Exposure to toluene caused decreased pup weights throughout lactation in F1 and F2 2000 ppm (both sexes treated), and 2000 ppm (females only treated) groups. Exposure at 2000 ppm to male parents only did not induce similar weight inhibition in offspring. The toluene offspring NOAEL is 500 ppm in groups in which maternal animals were exposed, and 2000 ppm for male only treated groups.     

Styrene Inhalation Toxicity Studies in Mice: II. Sex Differences in Susceptibility of B6C3F1 Mice

Styrene is a commercially important chemical used in the productionof plastics and resins. In initial short-term styrene inhalationstudies, toxicity was significantly greater in male B6C3F1 micethan in females, suggesting that males may metabolize styrenemore extensively and/or may be less able to detoxify reactivemetabolites. In addition, a nonlinear dose-response was observedwhere toxicity and mortality were greater in mice exposed to250 ppm than in those exposed to 500 ppm. These studies wereconducted to investigate potential mechanism(s) for sex differencesand the nonlinear dose-response in styrene toxicity by evaluatingthe effects of repeated styrene exposure on styrene oxide production,hepatic GSH availability, and hepatotoxicity in male and femaleB6C3F1 mice. Mice (36/sex/dose) were exposed to 0, 125, 250,or 500 ppm styrene 6 hr/day for up to 3 days. Styrene exposurecaused increased mortality and hepatotoxicity (centrilobularnecrosis, increased serum liver enzymes) in males and femalesafter one or two exposures to 250 and 500 ppm. Hepatic GSH levelswere decreased in a dose-dependent manner in males and females.After one exposure, GSH levels in males rebounded above controlsin all dose groups. After three exposures to 125 or 250 ppmmales appeared to maintain GSH levels; GSH was still decreasedin the 500 ppm group. GSH levels in females were decreased aftereach exposure in all dose groups to lower levels than in males,and did not rebound above controls. Male mice had significantlygreater blood styrene levels than females after one exposureto 500 ppm; however, there were no significant sex differencesin blood styrene after subsequent exposures. Levels of SO inblood were not significantly greater in male mice than femaleswithin a dose group, and did not change significantly with repeatedstyrene exposures for 3 days. Blood styrene and SO levels weresignificantly higher at 500 ppm than at 250 ppm indicating thatstyrene uptake and metabolism are greater at 500 ppm than at250 ppm. The higher incidence of mortality in male mice andthe nonlinear dose-response to styrene cannot be explained bygender- or dose-related differences in hepatotoxicity, GSH depletion,or blood styrene or SO levels.     

NTP toxicology and carcinogenesiss studies of citral (microencapsulated) (CAS No. 5392-40-5) in F344/N rats and B6C3F1 mice (feed studies)

Citral is used primarily as lemon flavoring in foods, beverages, and candies. It is also used as a lemon fragrance in detergents, perfumes, and other toiletries. Citral was nominated by the National Cancer Institute for study because of its widespread use in foods, beverages, cosmetics, and other consumer products and its structure as a representative beta-substituted vinyl aldehyde. Male and female F344/N rats and B6C3F1 mice were exposed to microencapsulated citral (greater than 96% pure) in feed for 14 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing starch microcapsules with a load of 31.3% citral. The concentration of citral in the diet was 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 345, 820, 1,785, and 1,585 mg citral/kg body weight to males and 335, 675, 1,330, and 2,125 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, all rats in the 31,300 ppm groups were killed moribund. Mean body weights of exposed males and females that survived to the end of the study were generally significantly less than those of the vehicle controls. Feed consumption by 15,600 and 31,300 ppm males and females was less than that by the vehicle controls during the first week of the study. Males and females in the 31,300 ppm groups exhibited listlessness, hunched posture, absent or slow paw reflex, and dull eyes. Exposure of rats to citral may have been associated with forestomach epithelial hyperplasia and hyperkeratosis, bone marrow atrophy and hemorrhage, and nephrotoxicity. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 745, 1,840, 3,915, and 8,110 mg/kg to males and 790, 1,820, 3,870, and 7,550 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, four males in the 31,300 ppm group were killed moribund. Mean body weights of all exposed groups of males and females were significantly less than those of the vehicle controls. Feed consumption by females exposed to 7,800 ppm or greater was less than that by the vehicle controls during the first week of the study. By the end of the study, feed consumption by all exposed groups was greater than that by the vehicle controls. Mice in the 15,600 and 31,300 ppm groups were generally thin and lethargic; a few males in the 7,800 ppm group were also thin. The incidences of ovarian atrophy were significantly increased in females exposed to 15,600 or 31,300 ppm. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,000, or 4,000 ppm microencapsulated citral for 2 years. Additional groups of 50 male and 50 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,000, and 4,000 ppm delivered average daily doses of approximately 50, 100, and 210 mg/kg to males and females. Survival of all exposed groups of males was significantly greater than that of the vehicle control group. Mean body weights of rats exposed to 4,000 ppm were generally less than those of the vehicle controls from week 49 (males) or 25 (females) to the end of the study. Feed consumption by exposed groups was similar to that by the vehicle controls. No neoplasms or nonneoplastic lesions were attributed to exposure to citral. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 500, 1,000, or 2,000 ppm microencapsulated citral for 2 years. Additional groups of 50 male and 50 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 500, 1,000, and 2,000 ppm delivered average daily doses of approximately 60, 120, and 260 mg/kg to males and females. Survival of exposed males and females was similar to that of the vehicle control groups. Mean body weights of mice exposed to 1,000 or 2,000 ppm were generally less than those of the vehicle controls throughout the study, and mean body weights of 500 ppm females were less from week 30 to the end of the study. Feed consumption by the exposed groups was similar to that by the vehicle controls. The incidences of malignant lymphoma occurred with a positive trend in female mice, and the incidence in 2,000 ppm females was significantly greater than that in the vehicle control group. Tissues most commonly affected by malignant lymphoma were the spleen, mesenteric lymph node, thymus, and, to a lesser extent, the ovary. GENETIC TOXICOLOGY: Citral was not mutagenic in S. typhimurium strain TA98, TA100, TA1535, or TA1537 with or without induced rat or hamster liver S9 enzymes. In cytogenetic tests with cultured Chinese hamster ovary cells, citral induced sister chromatid exchanges with and without S9, but chromosomal aberrations were not significantly increased after exposure to citral, with or without S9. Negative results were obtained in an in vivo bone marrow micronucleus test in male B6C3F1 mice treated by intraperitoneal injection with 250 to 750 mg/kg daily for 3 days. Likewise, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples collected from male and female mice within 24 hours of the final exposure in the 14-week study. In conclusion, citral gave negative results in in vitro and in vivo tests for genotoxicity, with the exception of the in vitro mammalian cell test for sister chromatid exchange induction CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of citral in male or female F344/N rats exposed to 1,000, 2,000, or 4,000 ppm. There was no evidence of carcinogenic activity of citral in male B6C3F1 mice exposed to 500, 1,000, or 2,000 ppm. There was equivocal evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of malignant lymphoma.     

Toxicology and carcinogenesis studies of tetralin (CAS No. 119-64-2) in F344/N rats and B6C3F1 mice (inhalation studies)

Tetralin is used as an industrial solvent primarily for naphthalene, fats, resins, oils, and waxes; as a solvent and stabilizer for shoe polishes and floor waxes; as a solvent for pesticides, rubber, asphalt, and aromatic hydrocarbons (e.g., anthracene); as a dye solvent carrier in the textile industry; as a substitute for turpentine in lacquers, paints, and varnishes; in paint thinners and as a paint remover; in alkali-resistant lacquers for cleaning printing ink from rollers and type; as a constituent of motor fuels and lubricants; for the removal of naphthalene in gas distribution systems; and as an insecticide for clothes moths. Tetralin was nominated by the National Cancer Institute for carcinogenicity and disposition studies because of its structure, high production volume, and high potential for worker and consumer exposure. Male and female F344/N rats and B6C3F1 mice were exposed to tetralin (at least 97% pure) by inhalation for 2 weeks, 3 months, or 2 years; male NCI Black Reiter (NBR) rats were exposed to tetralin by inhalation for 2 weeks. Male NBR rats do not produce 2u-globulin; the NBR rats were included to study the relationship of 2u-globulin and renal lesion induction. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male (F344/N and NBR) and five female (F344/N) rats were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 12 exposures. All rats survived to the end of the studies. The final mean body weight of female rats exposed to 120 ppm and mean body weight gains of female rats exposed to 30 ppm or greater were significantly less than those of the chamber controls. Final mean body weights of exposed groups of male NBR rats and mean body weight gains of all exposed groups of male rats were significantly less than those of the chamber controls. Dark-stained urine was observed in all 120 ppm rats. Squinting, weeping, or matted fur around the eyes were noted in the majority of F344/N rats exposed to 120 ppm. The 2u-globulin concentrations in the kidney of male F344/N rats were significantly greater in all exposed groups than in the chamber control group. The absolute kidney weight of 60 ppm females and the relative kidney weights of male F344/N rats exposed to 30 ppm or greater and female rats exposed to 15 ppm or greater were significantly increased. The absolute liver weight of 120 ppm NBR male rats and the relative liver weights of male and female rats exposed to 60 or 120 ppm were significantly increased. In the nose, the incidences of mononuclear cell cellular infiltration were generally significantly increased in all exposed groups of rats, and incidences of olfactory epithelium degeneration and glandular hypertrophy occurred in all male F344/N rats exposed to 120 ppm. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 13 exposures. All mice survived to the end of the study. Mean body weights of male and female mice were similar to those of the chamber controls. Dark-stained urine was observed in most of the exposed mice. The absolute and relative liver weights of 60 and 120 ppm males and 30 and 120 ppm females and the relative liver weights of 60 ppm females were significantly greater than those of the chamber controls. In the nose, the incidences of olfactory epithelium atrophy were significantly increased in 60 and 120 ppm males and females. Glandular dilatation occurred in all 120 ppm females, and glandular hyperplasia occurred in all 120 ppm males and females. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. The same exposure concentrations were given to additional groups of 10 male and 10 female clinical pathology study rats for up to 6 weeks and five male renal toxicity rats for 2 weeks. All rats survived to the end of the study. During the first 4 weeks of exposure, dark-stained urine was observed in the catch pans of rats exposed to 30, 60, or 120 ppm. Tetralin induced a minimal decrease in the erythron in both sexes that resulted in a hematopoietic response. Tetralin increased urine aspartate aminotransferase and urine lactate dehydrogenase activities (males and females) and glucose/creatinine ratio (males), suggestive of renal injury. The absolute kidney weights of 60 and 120 ppm females and the relative kidney weights of males and females exposed to 15 ppm or greater were significantly greater than those of the chamber controls. Concentrations of 2u-globulin in the kidney of exposed male rats were generally greater than those of the chamber controls at all time points and greater at 6 and 14 weeks than at 2 weeks. There were significantly increased incidences of olfactory epithelium necrosis in rats exposed to 30 ppm or greater and of olfactory epithelium regeneration in 60 and 120 ppm rats. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of 120 ppm males were significantly less than those of the chamber controls. Dark-stained urine was observed in the catch pans of mice exposed to 30, 60, or 120 ppm during the first month of the study. Tetralin induced a minimal decrease in the erythron in both sexes that resulted in a hematopoietic response. The relative liver weights of 120 ppm males and 30 ppm or greater females were significantly greater than those of the chamber controls. Incidences of olfactory epithelium metaplasia in 60 and 120 ppm males and females, respiratory epithelium hyaline droplet accumulation in 120 ppm males and 60 and 120 ppm females, cytoplasmic eosinophilic granules within the transitional epithelium lining the urinary bladder in all exposed groups of males and females, and ovarian atrophy and uterine atrophy in 60 and 120 ppm females were significantly increased. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to tetralin at air concentrations of 0, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 105 weeks. Additional groups of five male and five female rats were exposed to the same concentrations for 12 months. Survival of all exposed groups of rats was similar to that of the chamber controls. Mean body weights of 120 ppm females were 6% less than those of the chamber controls after week 29. Dark-stained urine was observed in all exposed groups of rats. Creatinine-adjusted levels of all urinary metabolites increased with increasing exposure concentration in males and females. In the standard evaluation of the kidney, there were slightly increased incidences of cortical renal tubule adenoma in male rats. In the combined analysis of single and step sections, the incidence of cortical renal tubule adenoma was significantly increased in the 120 ppm group. In the combined analysis, there was also a significantly increased incidence of renal tubule hyperplasia in the 120 ppm group. In 120 ppm males in the standard evaluation, the severity of chronic nephropathy was increased and the incidence of transitional epithelial hyperplasia in the renal pelvis was significantly increased. Three hepatocellular adenomas occurred in 120 ppm females, and one hepatocellular carcinoma each was observed in the 60 and 120 ppm groups. The incidences of uterine stromal polyp and endometrium hyperplasia were significantly increased in 120 ppm females. Incidences of interstitial cell adenoma and germinal epithelium atrophy of the testis in 30 and 120 ppm males were significantly greater than those in the chamber controls. The incidences of olfactory epithelium degeneration, metaplasia, basal cell hyperplasia, suppurative inflammation, and mineralization (except 30 ppm females) in the nose were significantly increased in all exposed groups of rats. The incidences of glandular dilatation were significantly increased in 120 ppm males and all exposed groups of females. The incidences of respiratory epithelium chronic inflammation were significantly increased in males exposed to 60 or 120 ppm and all exposed groups of females. The incidences of lens cataract in 120 ppm females were significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to tetralin at air concentrations of 0, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 105 weeks. Additional groups of five male and five female mice were exposed to the same concentrations for 12 months. Survival of 60 and 120 ppm female mice was significantly greater than that of the chamber controls. The mean body weights of all exposed groups of male and female mice were similar to those of the chamber controls by the end of the study. Dark-stained urine was observed in all exposed groups of male mice and in females exposed to 60 or 120 ppm. Creatinine-adjusted levels of all urinary metabolites increased with increasing exposure concentration in males and females. The incidence of hemangiosarcoma of the spleen was increased in 120 ppm females and exceeded the historical control range for inhalation studies. The incidences of olfactory epithelium atrophy, respiratory metaplasia, glandular hyperplasia, and suppurative inflammation in exposed groups of mice were significantly greater than those in the chamber controls. Transitional epithelium cytoplasmic eosinophilic granules were present in the urinary bladder of all exposed mice. (ABSTRACT TRUNCATED)     

Subchronic Toxicity of 4-Vinylcyclohexene in Rats and Mice by Inhalation Exposure

This study was conducted to evaluate the subchronic toxicityof 4-vinylcyclohexene (VCH). Male and female Sprague–Dawleyrats and B6C3F₁ mice were exposed by inhalation to VCH 6 hr/day, 5 days/week for 13 weeks. Rats were exposed to 0, 250,1000, or 1500 ppm, and mice were exposed to 0, 50, 250, or 1000ppm. In addition, another group of rats and mice was exposedto 1000 ppm butadiene so that a comparison could be made betweenthe two compounds. Exposure to 1000 ppm VCH resulted in deathsof all male mice and 5/10 female mice on Test Days 11 or 12.Three additional female mice exposed to 1000 ppm VCH died priorto study completion. The most notable compound-related clinicalsign was lethargy observed in the 1500 ppm VCH-exposed ratsand 1000 ppm VCH-exposed mice. Male rats exposed to 1500 ppmVCH had significantly lower body weights compared to controls,and male and female rats in the 1500 ppm group had signifi cantlylower body weight gains. None of the VCH-exposed animals orbutadiene-exposed rats showed any compound-related hemato logicaleffects. However, mice exposed to 1000 ppm butadiene exhibitedmild macrocytic anemia. Clinical chemistry evaluation and urinalysisshowed no compound-related effects in rats exposed to eitherVCH or butadiene. Male and female rats exposed to 1000 or 1500ppm VCH or 1000 ppm butadiene had increased absolute and/orrelative liver weights, and male rats in these same exposuregroups had increased relative kidney weights. Microscopically,in creased accumulation of hyaline droplets was observed inthe kid neys of male rats from all VCH exposure groups. Althoughcompound–related, the droplets were not accompanied bycytotoxicity. In mice, the most notable adverse histopathologicaleffect was ovarian atrophy in females exposed to 1000 ppm VCHor 1000 ppm butadiene. The atrophy was slightly more severein the VCH exposed females than in the butadiene–exposedfemales. There were no other compound–related pathologicaleffects in male or female mice exposed to VCH. Additionally,butadiene–exposed male mice had decreased testicular weights,accompanied by slight testicular degeneration and atrophy. ForVCH exposure, the no–observed-adverse–effect–levelis 1000 ppm for rats based on leth argy and lowered body weightsand 250 ppm for mice based on mortality and ovarian atrophy.     

Chronic treatment with polychlorinated biphenyls (PCB) during pregnancy and lactation in the rat: Part 1: Effects on somatic growth, growth hormone-axis activity and bone mass in the offspring

Polychlorinated biphenyls (PCBs) are pollutants detected in animal tissues and breast milk. The experiments described in the present paper were aimed at evaluating whether the four PCB congeners most abundant in animal tissues (PCB-138, -153, -180 and -126), administered since fetal life till weaning, can induce long-term alterations of GH-axis activity and bone mass in the adult rat. We measured PCB accumulation in rat brain and liver, somatic growth, pituitary GH expression and plasma hormone concentrations at different ages. Finally, we studied hypothalamic somatostatin expression and bone structure in adulthood, following long-term PCB exposure.Dams were treated during pregnancy from GD15 to GD19 and during breast-feeding. A constant reduction of the growth rate in both male and female offspring from weaning to adulthood was observed in exposed animals. Long-lasting alterations on hypothalamic-pituitary GH axis were indeed observed in PCB-exposed rats in adulthood: increased somatostatin expression in hypothalamic periventricular nucleus (both males and females) and lateral arcuate nucleus (males, only) and decreased GH mRNA levels in the pituitary of male rats. Plasma IGF-1 levels were higher in PCB-exposed male and female animals as compared with controls at weaning and tended to be higher at PN60. Plasma testosterone and thyroid hormone concentrations were not significantly affected by exposure to PCBs. In adulthood, PCBs caused a significant reduction of bone mineral content and cortical bone thickness of tibiae in male rat joint to increased width of the epiphyseal cartilage disk. In conclusion, the developmental exposure to the four selected PCB compounds used in the present study induced far-reaching effects in the adult offspring, the male rats appearing more sensitive than females.     

Comparison of Styrene Hepatotoxicity in B6C3F1 and Swiss Mice

Inhalation exposure to styrene at concentrations that causemetabolic saturation results in significantly greater hepatotoxicityin B6C3F1 mice than in Swiss mice; females of both strains aremore susceptible than males. These studies were conducted toinvestigate the mouse strain and gender differences in susceptibilityto hepatotoxicity caused by repeated exposure to styrene atconcentrations that do not cause metabolic saturation. Maleand female B6C3F1 and Swiss mice (8 weeks old) were exposedto 0, 150, or 200 ppm styrene for 6 hr/day, 5 days/week, forup to 2 weeks. Changes in body and liver weights, serum alanineaminotransferase (ALT) and sorbitol dehydrogenase (SDH) levels,liver histopathology, and total liver glutathione (GSH) wereevaluated after 2, 3, 5, and 10 exposures (six mice/sex/strain/timepoint/concentration). Blood levels of styrene and styrene-7,8-oxide(SO) were measured in mice exposed to 200 ppm styrene for 2,3, or 5 days (six mice/sex/strain/time point/concentration).Serum ALT and SDH levels were significantly elevated only infemale B6C3F1 mice after 3 exposures to 200 ppm styrene; enzymelevels had returned to control levels when measured after 5and 10 exposures. Degeneration and coagulative necrosis of centrilobularhepatocytes were observed in female B6C3F1 mice exposed 2, 3,and 5 days to 150 or 200 ppm styrene; incidences of these lesionswere greater in the 200 ppm than in the 150 ppm dose group.After 10 days of exposure to 150 or 200 ppm styrene, hepatocellularlesions had resolved, although a residual chronic inflammationwas present in livers of most female B6C3F1 mice. Degenerationof centrilobular hepatocytes was observed in one male B6C3F1mouse after 3 exposures to 200 ppm, and no significant lesionswere observed in livers of exposed Swiss mice. Significant dose-relateddecreases in hepatic GSH were observed in both sexes of bothstrains throughout the 2-week exposure. In general, hepaticGSH depletion was greatest in female B6C3F1 mice. Exposure to200 ppm caused 60–70% GSH depletion in female B6C3F1 miceat each time point. GSH depletion generally decreased in B6C3F1mice and increased in Swiss mice with continued exposure to150 ppm styrene. With continued exposure to 200 ppm, GSH depletiongenerally decreased in all mice. Blood styrene and SO levelsincreased in all groups with the number of exposures. Styrenelevels were significantly higher in B6C3F1 mice than in Swissmice; however, within each strain gender differences were notsignificant. These data suggest that the transient hepatotoxicityin female B6C3F1 mice was related to greater hepatic GSH depletionand/or slower GSH regeneration in these animals.     

Subchronic toxicity and carcinogenicity studies of 1,2-dichloropropane inhalation to mice

Abstract

The subchronic toxicity and carcinogenicity of 1,2-dichloropropane (DCP) in male and female B6D2F1 mice exposed to DCP by inhalation for 13 weeks or for 2 years was investigated. The DCP concentrations used were 50, 100, 200, 300 or 400?ppm (v/v) in the 13-week study, and 32, 80 or 200?ppm (v/v) in the 2-year study. Thirteen weeks inhalation exposure of mice to DCP caused death in the mice exposed to 300?ppm and above, and was found to induce hemolytic anemia and lesions of the liver, forestomach and heart. Two years exposure to DCP significantly increased the combined incidence of bronchiolo-alveolar adenomas and carcinomas in females and marginally increased the incidence of Harderian gland adenomas in males. As non-neoplastic lesion, atrophy and respiratory metaplasia in the olfactory epithelium, and respiratory metaplasia in the submucosal gland of the nasal cavity were increased. Thus, two years inhalation exposure to DCP is carcinogenic in female mice and there is a marginal evidence of carcinogenicity in males.     

Toxicology and carcinogenesis studies of divinylbenzene-HP (Cas No. 1321-74-0) in F344/N rats and B6C3F1 mice (inhalation studies)

Divinylbenzene-HP is used for producing vinyl polymers. Divinylbenzene-HP was nominated for study by the National Cancer Institute because of the potential for worker exposure and the structural similarity of divinylbenzene to styrene, a potential human carcinogen. Male and female F344/N rats and B6C3F1 mice were exposed to divinylbenzene-HP (80%) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study. Significant decreases in mean body weights occurred in both male and female rats in the 400 ppm groups. Relative kidney weights of 50 ppm or greater males and relative liver weights of 200 and 400 ppm males were significantly greater than those of the chamber controls. A clear serous nasal/eye discharge was observed in groups of males exposed to 100 ppm or greater and females exposed to 50 ppm or greater. Minimal or mild rhinitis occurred in 400 ppm rats of both sexes. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. All 400 ppm males and females died on or before the second day of the study, and two male and two female 200 ppm mice died early. Mean body weights of 100 and 200 ppm males were significantly less than those of the chamber controls. Thymus weights of exposed groups of males were significantly less than those of the chamber controls, and relative liver weights of 100 and 200 ppm males were significantly increased. Kidney and liver weights of exposed groups of females were significantly greater than those of the chamber controls. Mice exposed to 200 and 400 ppm had liver lesions including degeneration, necrosis, hemorrhage or cytomegaly. Renal tubule necrosis and regeneration occurred at 200 ppm. Necrosis or metaplasia of nasal epithelium and glands occurred in the nose in all exposure groups. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to divinylbenzene-HP at concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. There were no biologically significant changes in body weight in either sex. Nasal/eye discharge was noted in 400 ppm males and 100 ppm females. Kidney and liver weights of exposed groups of males and of 400 ppm females were generally greater than those of the chamber controls. In addition, the relative weights of the heart and testis were significantly increased in 200 and 400 ppm males. Incidences of degeneration of the olfactory epithelium in 200 and 400 ppm rats and basal cell hyperplasia of the olfactory epithelium in rats exposed to 100 ppm or greater were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to divinylbenzene-HP at concentrations of 0, 12.5, 25, 50, 100, or 200 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All 200 ppm males and nine 200 ppm females died early. Final mean body weights were significantly lower in males and females exposed to 25, 50, or 100 ppm when compared with chamber controls. Lethargy or hypoactivity was observed in the higher exposure concentration groups. Exposure to divinylbenzene was associated with necrosis of the liver and kidney in 200 ppm males and females dying early. In all exposed groups of male and female mice, there was necrosis of nasal cavity lateral walls, olfactory epithelium, and glands with resultant atrophy of olfactory epithelium and glands in females. A lower number of animals had necrotic or degenerative changes of the upper respiratory tract. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to divinylbenzene-HP at concentrations of 0, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of 400 ppm females was significantly less than that of the chamber control group. Survival of all exposed groups of males was similar to that of the chamber control group. Mean body weights of 400 ppm males and females were significantly less than those of the controls during the second half of the study. Renal tubule carcinomas occurred in two of 50 males exposed to 400 ppm in the original kidney sections, an incidence that exceeded the historical control range. In 400 ppm males, the incidence of renal tubule hyperplasia was increased, and the incidence of nephropathy was significantly increased. Following combined analysis of single and step-section data, the incidences of renal tubule adenoma and adenoma or carcinoma (combined) were marginally higher in 200 and 400 ppm males, and the incidence of renal tubule hyperplasia was significantly increased in 400 ppm males. The incidences of malignant glial cell tumors (malignant astrocytoma and oligodendroglioma) in the brain were slightly increased in 100 and 200 ppm males, and the incidence in the 200 ppm group exceeded the historical range for chamber controls. There were increased incidences of degenerative and regenerative changes in the olfactory epithelium in the nose of all exposed groups of rats. The incidence of focal chronic inflammation in the lung of 400 ppm males was significantly greater than in the chamber control group. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to divinylbenzene-HP at concentrations of 0, 10, 30, or 100 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of all exposed groups of male and female mice was similar to that of the chamber controls. Mean body weights were lower relative to chamber controls in 100 ppm males and in 30 and 100 ppm females. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in 100 ppm males were greater than chamber control incidences, but the incidences of adenoma or carcinoma (combined) were within the historical control range. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in all exposed groups of females were generally greater than those of the chamber controls; the incidences were at the upper end or exceeded the historical control ranges. There was a greater incidence and severity of alveolar epithelial hyperplasia in 100 ppm females and a greater severity of this lesion in 30 ppm females, when compared to chamber controls. The incidences and/or severities of atypical bronchiole hyperplasia were significantly increased in all exposed groups of mice. Nonneoplastic nasal lesions occurred in most exposed mice. GENETIC TOXICOLOGY: Divinylbenzene-HP was not mutagenic in any of three independent gene mutation assays using Salmonella typhimurium strains TA97, TA98, TA100, TA1535, or TA1537 or Escherichia coli tester strain WP2 uvrA with or without induced hamster or rat liver enzymes. No increases in the frequencies of micronucleated normochromatic erythrocytes or alterations in the percentages of polychromatic erythrocytes were seen in peripheral blood of male or female B6C3F1 mice exposed to divinylbenzene-HP by inhalation for 3 months. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was equivocal evidence of carcinogenic activity of divinylbenzene-HP in male F344/N rats based upon the occurrence of carcinomas in the kidney and glial tumors in the brain. There was no evidence of carcinogenic activity in female F344/N rats exposed to 100, 200, or 400 ppm divinylbenzene-HP. There was no evidence of carcinogenic activity in male B6C3F1 mice exposed to 10, 30, or 100 ppm divinylbenzene-HP. There was equivocal evidence of carcinogenic activity of divinylbenzene-HP in female B6C3F1 mice based on the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in the lung. Exposure to divinylbenzene-HP caused nonneoplastic lesions of the nasal cavity in male and female rats and of the lung and nasal cavity in male and female mice.     

Toxicology and carcinogenesis studies of goldenseal root powder (Hydrastis Canadensis) in F344/N rats and B6C3F1 mice (feed studies)

Goldenseal root powder is used in folk medicine for the treatment of gastrointestinal disturbances, urinary disorders, hemorrhage, skin, mouth, and eye infections, and inflammation. The major alkaloids in goldenseal are berberine, hydrastine, and canadine. Goldenseal root powder was nominated for study by the National Institute of Environmental Health Sciences based on the potential for human exposure and the lack of carcinogenicity data, and because it is one of the most widely used herbs in the United States. Male and female F344/N rats and B6C3F1 mice were exposed to ground goldenseal root powder in feed for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 155, 315, 630, 1,190, 2,465, and 4,815 mg goldenseal root powder/kg body weight for males and 150, 290, 640, 1,240, 2,370, and 4,870 mg/kg for females) for 15 days. All rats survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Liver weights of males exposed to 6,250 ppm or greater and females exposed to 12,500 ppm or greater were significantly greater than those of the controls. Minimal to moderate hepatocellular hypertrophy occurred in three males and all females exposed to 25,000 ppm and in all 50,000 ppm males and females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 380, 840, 1,760, 3,435, 6,700, and 15,170 mg/kg body weight for males and 330, 670, 1,240, 2,375, 4,760, and 8,475 mg/kg for females) for 15 days. All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Significant increases in liver weights occurred in males exposed to 25,000 and 50,000 ppm and in females exposed to 50,000 ppm. Absolute and relative thymus weights of 12,500 and 50,000 ppm males were significantly decreased. Minimal hypertrophy of centrilobular hepatocytes occurred in all males and females exposed to 50,000 ppm. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 255, 500, 1,000, 2,020, and 4,060 mg/kg for males and 260, 500, 1,030, 2,070, and 4,100 mg/kg for females) for 14 weeks. Additional groups of 10 male and 10 female clinical pathology study rats were given the same concentrations for 23 days. All rats survived to the end of the study. None of the body weights or mean body weight gains were significantly different from those of the controls. Feed consumption by exposed groups was generally similar to that by controls throughout the study. Liver weights were significantly increased in males exposed to 6,250 ppm or greater and in all exposed groups of females. The incidences of hepatocyte hypertrophy were significantly increased in the liver of males and females exposed to 12,500 ppm or greater; cytoplasmic vacuolization of hepatocytes occurred in all exposed males. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 680, 1,360, 2,260, 5,370, and 10,550 mg/kg for males and 590, 1,250, 2,345, 4,790, and 10,740 mg/kg for females) for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 50,000 ppm and females exposed to 25,000 or 50,000 ppm were significantly less than those of the controls. Feed consumption by 3,121, 6,250, 12,500, 25,000, and 50,000 ppm males was similar to that by controls. Liver weights were significantly increased in males exposed to 12,500 ppm or greater and in females exposed to 25,000 or 50,000 ppm. The left epidydimal weight in male mice was significantly decreased relative to controls. The incidences of hepatocyte hypertrophy were significantly increased in males and females exposed to 12,500 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 135, 400, and 1,175 mg/kg for males and 150, 470, and 1,340 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly greater than that of the controls. Mean body weights of females exposed to 9,000 ppm were 6% less than those of the controls after week 37, and those of 25,000 ppm females were 6% less than those of the controls after week 8. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. The incidences of hepatocellular adenoma were significantly increased in males and females exposed to 25,000 ppm, and the incidence of hepatocellular adenoma or carcinoma (combined) was significantly increased in 25,000 ppm males. All exposed groups of males and females had significantly increased incidences of hepatocyte hypertrophy. The incidences of hepatocyte degeneration were significantly increased in all exposed groups of males and in 9,000 and 25,000 ppm females. The incidences of eosinophilic focus were significantly increased in 9,000 and 25,000 ppm males and all exposed groups of females. The incidences of cardiomyopathy were significantly decreased in all exposed groups of males and in 25,000 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 375, 1,120, and 3,275 mg/kg for males and 330, 1,000, and 2,875 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly less than that of the controls. Mean body weights of females exposed to 25,000 ppm were 3% to 9% less than those of the controls after week 13, 6% less for weeks 14 to 52, and 5% less for weeks 53 to 101. Feed consumption by exposed groups of males and females was generally similar to that of the controls throughout the study. The incidences of hepatocellular adenoma occurred with a positive trend in males, and the incidences of multiple hepatocellular adenoma were significantly increased in 9,000 and 25,000 ppm males. The incidences of hepatoblastoma occurred with a positive trend in males with a marginal increase in the 25,000 ppm group. Significantly increased incidences of eosinophilic focus or mixed cell focus occurred in all exposed groups of males. GENETIC TOXICOLOGY: Goldenseal root powder was not mutagenic in Salmonella typhimurium or Escherichia coli tester strains, with or without liver S9 metabolic activation enzymes. In addition, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples from mice exposed to goldenseal root powder in feed for 3 months. Berberine chloride was also tested for mutagenicity in standard screening assays. No mutagenicity was observed in several tester strains of Salmonella typhimurium, with or without rat or hamster liver S9 metabolic activation enzymes. In an acute exposure assay, no increase in the frequency of micronucleated polychromatic erythrocytes was seen in bone marrow of male mice administered three intraperitoneal injections of berberine chloride at 24-hour intervals. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenic activity of goldenseal root powder in male F344/N rats based on the increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of goldenseal root powder in female F344/N rats based on the increased incidence of hepatocellular adenoma. There was some evidence of carcinogenic activity of goldenseal root powder in male B6C3F1 mice based on the increased incidences of hepatoblastoma and multiple hepatocellular adenoma. There was no evidence of carcinogenic activity of goldenseal root powder in female B6C3F1 mice exposed to 3,000, 9,000, or 25,000 ppm goldenseal root powder in feed for 2 years. Administration of goldenseal root powder resulted in increased incidences of nonneoplastic lesions in the liver of male and female rats and male mice.     

Subchronic Inhalation Studies of Styrene in CD Rats and CD-1 Mice

Groups of 10 male and 10 female Charles River (CRL) CD (Sprague-Dawley-derived)rats were exposed to styrene vapor at 0, 200, 500, 1000, or1500 ppm 6 hr per day 5 days per week for 13 weeks. Styrenehad no effect on survival, hematology, or clinical chemistry.Males at 1500 ppm weighed 10% less after 13 weeks and malesand females at 1000 and 1500 ppm consumed more water than controls.Histopathologic changes were confined to the olfactory epitheliumof the nasal mucosa. Groups of 20 male and 20 female CRL CD-1and B6C3F1 mice were exposed to styrene vapor at 0, 15, 60,250, or 500 ppm 6 hr per day 5 days per week for 2 weeks. Mortalitywas observed in both CD-1 and B6C3F1 mice exposed to 250 or500 ppm; more female mice, but not males, died from exposureto 250 ppm than from 500 ppm. Groups of 10 male and 10 femaleCRL CD-1 mice were exposed to styrene vapors at 0, 50, 100,150, or 200 ppm 6 hr per day 5 days per week for 13 weeks. Twofemales exposed to 200 ppm died during the first week. Livertoxicity was evident in the decedents and in some female survivorsat 200 ppm. Changes were observed in the lungs of mice exposedto 100, 150, or 200 ppm and in the nasal passages of all treatmentgroups, those exposed to 50 ppm being less affected. Satellitegroups of 15 male rats and 30 male mice were exposed as describedabove for 2, 5, or 13 weeks for measurement of cell proliferation(BrdU labeling). No increase in cell proliferation was foundin liver of rats or mice or in cells of the bronchiolar or alveolarregion of the lung of rats. No increase in labeling index oftype II pneumocytes was seen in mouse lungs, while at 150 and200 ppm, an increased labeling index of Clara cells was seenafter 2 weeks and in occasional mice after 5 weeks. Large variationsin the labeling index among animals emphasize the need for largegroup sizes. For nasal tract effects, a NOAEL was not foundin CD-1 mice, but in CD rats, the NOAEL was 200 ppm. For othereffects, the NOAEL was 500 ppm in rats and 50 ppm in mice.