Short-term Toxicity Studies Research Articles

Historical data of neoplastic and non-neoplastic lesions in B6C3F1(C57BL/6CrSlc*C3H/HeSlc) mice.

Historical data are presented for neoplastic and non-neoplastic lesions in B6C3F1 (C57BL/6×C3H) mice that served as controls for short-term toxicity, long-term toxicity and carcinogenicity studies conducted at the Biosafety Research Center, Foods, Drugs, and Pesticides, (An-Pyo Center) during a 12-yr period (1980-1992). Patterns consistent with spontaneouslly-occurring tumors in specific organs were found in male and female mice and were similar to those reported in the literature. The incidence of most of the neoplastic and non-neoplastic lesions increased with age, suggesting that these pathological alterations are age-associated processes. However, some were believed to be caused by latent viral infections, nutritional or hormone-dependent factors. The wide variety and a high incidence of these lesions seen in long-term studies may greatly complicate histopathological evaluations and the elucidation of treatment-related effects. Consequently, both quantitative and qualitative interpretations are needed for meaningful evaluations.

Validation of an improved nose-only exposure system for rodents.

Several types and modifications of nose-only inhalation chambers for exposing rodents are described. The improvement of this 'flow-past' -like nose-only exposure system is that it is modular, i.e. it can be used for acute studies with a maximum of 20 rodents (one segment) or for chronic inhalation studies with 100 (or more) rodents per chamber with five (or more) segments. Another goal was to design a nose-only exposure system that provides maximal computer support and automatization, as well as robust aerosol collection conditions. The evaluation of the five-segment chamber, charged with 98 rats, revealed that a flow rate of 0.75 l air min-1 or approximately 2.5 times the rat minute ventilation volume per exposure port is sufficient to provide homogeneous temporal and spatial exposure conditions. Also, the aerosol size distribution was constant throughout the chamber. Experimental data suggest that computer-controlled sampling of the test atmosphere up to ca. 6 l air min-1 did not alter the flow dynamics of the exposure system. The nose-only inhalation chamber developed is suitable for short-term and long-term inhalation toxicity studies using small laboratory rodents with minimal consumption of test compound.

Final Report on the Safety Assessment of Ethyl Ester of PVM/MA Copolymer and Butyl Ester of PVM/MA Copolymer

Ethyl Ester of PVM/MA Copolymer and Butyl Ester of PVM/MA Copolymer are polymers consisting of the partial ethyl ester and butyl ester, respectively, of the polycarboxylic resin formed from vinyl methyl ether and maleic anhydride. These esters are used in cosmetic formulations as film formers and hair fixatives. Ethyl Ester and Butyl Ester of PVM/MA Copolymer had oral LD50s for rats of >25.6 g/kg. Butyl Ester of PVM/MA Copolymer was not toxic in a short-term oral toxicity study. Neither ester was toxic in subchronic inhalation animal studies and were neither ocular or dermal primary irritants. Neither was a skin irritant, sensitizer, or photosensitizer when assayed in human volunteers. Butyl Ester of PVM/MA Copolymer was not mutagenic in a mouse forward mutation assay with or without metabolic activation, and was inactive in an unscheduled DNA Synthesis assay. This ingredient was weakly active in the in vitro transformation of Balb/3T3 cells assay. On the basis of the animal and clinical data presented in this report, it is concluded that Ethyl Ester of PVM/MA Copolymer and Butyl Ester of PVM/MA Copolymer are safe in a neutralized form as cosmetic ingredients in the present practices of use.

Toxicity studies of Caramel Colour III and 2-acetyl-4(5)-tetrahydroxybutylimidazole in F344 rats

Caramel Colour III is used as a colour additive in beers and a variety of foods. Beer is the most important single source of Caramel Colour III in the diet although consumption of dark beers has been decreasing in recent years. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has established an acceptable daily intake of 200 mg/kg/day for Caramel Colour III. The safety of Caramel Colour III has been questioned during recent years following feeding studies in the rat that were associated with reduced white cell and lymphocyte counts. These effects have been attributed to the presence of 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI) in this class of caramel colour. Short-term oral toxicity studies were conducted on low-THI and high-THI samples of Caramel Colour III (13 wk) and on a sample of THI (28 days). In both studies, the test materials were mixed with demineralized water and the solutions were given to the animals ad lib. in the drinking fluid. In the 13-wk subchronic toxicity study of Caramel Colour III, groups of 20 rats/sex were given concentrations of caramel colour equivalent to intakes of 0, 10, 15 or 20 g low-THI caramel colour/kg body weight/day or 20 g/kg of a high-THI caramel colour. In the 4-wk toxicity study with THI, groups of 20 rats/sex were given 0, 8 or 64 ppm THI (equivalent to approx. 0, 0.9 or 7.2 mg/kg/day) and 10 rats/sex were given 1, 2, 4, 16 or 32 ppm THI (equivalent to approx. 0.1, 0.2, 0.5, 1.9 or 3.7 mg/kg/day) for 4 wk followed by a 2-wk recovery phase for 10 rats/sex in the 0, 8 and 64 ppm groups. Rats given Caramel Colour III had soft faeces; there were no other treatment-related clinical observations and no treatment-related deaths occurred. All treated groups given Caramel Colour III had lower food and fluid consumption than controls. Males given 15 or 20 g low-THI caramel colour/kg or 20 g high-THI caramel colour/kg and females given 20 g/kg of either type had lower body weights than controls. In the 4-wk toxicity study with THI, there were no treatment-related ante-mortem observations, and no effects on body weights or food consumption. Fluid consumption by males and females treated with 64 ppm THI was lower than that of controls. Haematological changes noted in both studies included lower total white blood cell and lymphocyte (absolute and percentage) counts, and higher absolute and percentage neutrophil counts; these changes returned to normal by study termination in the caramel colour study, and by the third day post-treatment in the THI study. There were no consistent treatment-related alterations in blood chemistry or urinalysis variables for either study, and any changes noted were not associated with macroscopic or microscopic pathological alterations. There were no toxicologically important pathological findings for either study. Based on these studies the no-observed-adverse-effect level (NOAEL) for low-THI Caramel Colour III was considered to be 20 g/kg body weight. The acceptable daily intake for this caramel colour established by JECFA is 200 mg/kg body weight. The NOAEL for THI was found to be 0.38 mg/kg body weight for male rats and 0.12 mg/kg body weight for females.

5 Final Report on the Safety Assessment of Jojoba Oil and Jojoba Wax

Jojoba Oil is obtained from seeds of the desert shrub, Jojoba ( Simmondsia chinensis) and is used in cosmetic products at concentrations ranging from ≥ 0.1% to 25.0%. The oral LD50 for male rats is greater than 21.5 ml/kg. Results from short-term oral toxicity studies of Jojoba Oil indicated no treatment-related effects. Only slight conjunctival hyperemia was observed in the eyes of rabbits 1 h after the instillation of Jojoba Oil. Reactions had cleared by 24-h post-instillation. No significant skin irritation reactions were observed in albino guinea pigs patch tested with undiluted Jojoba Oil. In a maximization test, no sensitization reactions were observed in 20 male and female albino marmots patch tested with 10.0% Jojoba alcohol. A mixture of Jojoba Oil and hydrogenated Jojoba Wax was not mutagenic, with and without activation, in the Ames assay. A topical oil product containing 0.5% Jojoba Oil and a lip balm product containing 20.0% Jojoba Oil were classified as nonirritants and nonsensitizers to humans. Sensitization reactions to undiluted Jojoba Oil were not observed in a group of 28 patients with no known sensitivities. On the basis of the available animal and clinical data presented in this report, it is concluded that Jojoba Oil and Jojoba Wax are safe as cosmetic ingredients in the present practices of use and concentration.

Toxicology of Volatile Organic Compounds in Indoor Air and Strategy for Further Research

Indoor air is a variable complex mixture of chemicals and airborne particles. Volatile organic compounds (VOC) constitute a major group of indoor air pollutants encompassing diverse chemicals such as aldehydes, terpenes. and aromatic, aliphatic and halogenated hydrocarbons. Of many of these compounds, our knowledge of their possible health effects is very limited. To improve the situation, combined information should be assembled about the nature of VOC, the degree of human exposure, the number of people exposed and, most importantly, the toxicology of VOC. Evidence of carcinogenic potential in animals is convincing for formaldehyde and acetaldehyde vapor. Formaldehyde carcinogenesis is a highdose phenomenon with a determining role for cytolethahty. This may also be true for acetaldehyde carcinogenesis, but further studies are needed to verify this assumption. Being a reactive, potent DNA-protein cross-linker and a major indoor air contaminant, acrolein should be tested in a long-term rat inhalation carcinogenicity study. Studies with combinations of aldehydes, including superimposed peak exposures, would contribute a great deal to a realistic health hazard assessment of this class of compounds. Short-term inhalation toxicity studies, including toxicokinetics of a number of relevant terpenes. are deemed desirable to find out whether this category of chemicals forms a priority indoor air issue. Benzene is a human carcinogen at high hemotoxic exposure levels. There is evidence to suggest that at non-hemotoxic exposure concentrations the risk of leukemia decreases more than proportionally, soon becoming negligibly small. In comparison with benzene, detoxification of toluene and xylene is rapid which may explain the non-carcinogenicity of these benzene homologues. In nonoccupational situations, indoor air hexane concentrations are orders of magnitude lower than exposure levels associated with clinically overt neuropathy. Therefore, hexane is not regarded as an indoor air pollutant of major concern. Main elements of a strategy for further toxicological studies of (VOC in) indoor air include: (a) setting of priorities for testing individual compounds, classes of compounds and combinations of compounds; (b) identification of the type of information to be assembled; (c) prediction and experimental verification of synergism or additiveness between compounds; (d) application of biologically or physiologically based pharmacokinetic modelling to optimize extrapolation of toxicodynamic data obtained in fixed-time animal experiments to low-dose/long-time human situations, and (e) (geno)toxicity testing of relevant existing combinations of chemicals (e.g. 20 to 30) at concentrations of, e.g., a factor 3 or 10 higher than those occurring in indoor air. Studies along the lastmentioned practical line may be very helpful in narrowing down the number of indoor situations of real health concern.

Retroviral therapy and clinical trials for HIV-infected children

Antiretroviral therapy in children has built on advances in the treatment of HIV-infected adults, in conjunction with an appreciation of the developmental impact of AIDS in children and the different clinical manifestations and altered pharmacokinetics of drugs in the pediatric population. The first effective drug for the treatment of AIDS is the dideoxynucleoside AZT. This drug's principal mode of action is to block HIV replication by inhibition of the DNA polymerase reverse transcriptase. 1 In a double-blind placebo-controlled study of adults with AIDS and advanced AIDS-related complex, patients treated with AZT had improved survival and decreased incidence of opportunistic infections2; this study led to approval by the Food and Drug Administration of the drug for use in the treatment of adults with AIDS. In this study, clinical status, T lymphocyte counts, and surrogate markers of viral activity also improved. However, therapeutic effects were offset against significant bone marrow toxicity, resulting in dose-limiting neutropenia and anemia that required transfusion) Treatment with AZT was introduced to pediatric patients with HIV infection on the basis of successful interventions in adults. Initial dose ranging, safety, and shortterm toxicity studies in children indicated a safety profile similar to that in adults. In a dose escalation study in children between the ages of 5 months and 13 years, neutropenia (defined as <750 cells/ram 3) occurred in 25%, and anemia requiring transfusion in 20%; this study included sequential intravenous and oral therapy. 4 Infectious complications of HIV-1 infection continued to occur despite therapy, and included 22 catheter-related infections in 13 patients, otitis media, sinusitis, impetigo, and localized cellulitis. However, only two of these infections were temporally related to neutropenia. Of note is that the frequency of viral isolation from individual patients did not change over the period of the study. In a limited number of patients for whom data were available, viral cultures from cerebrospinal fluid tended to become negative. This study also

Oral Toxicity of Formaldehyde and Its Derivatives

Formaldehyde (FA) has been commercially produced since the early 1900s. Its widespread use in a variety of applications is known to result in appreciable exposure of workers and of a section of the general population. Formaldehyde is a normal metabolite in mammalian systems. It occurs in air as a product of the natural photooxidation of automobile exhaust, combustion processes, incinerators; formaldehyde has been found in municipal and industrial effluents and is present in food either naturally (fruits and vegetables, in the order of parts per million), or as a result of its use as a food additive. The use of FA and its derivative, hexamethylenetetramine (HMT), which gradually decomposes to FA under acidic conditions as antimicrobial agents in food, raises questions about their potential chronic oral toxicity. Furthermore, since FA is a very reactive compound and reacts with different macromolecules such as proteins and nucleic acids, the safety evaluation of FA as a cheese additive must take into account the toxicity of the reaction products between FA and milk components. Biochemical aspects, acute and short-term toxicity studies including mutagenicity, multigeneration, and reproduction studies, long-term carcinogenicity studies after oral administration of FA and HMT are reviewed in this paper. The results of these studies indicate that repeated oral exposure of a relatively large amount of FA that could overwhelm the normal metabolic capacity of animals to convert FA into formiate, CO2, and water produces histopathological gastric changes. This paper correlates the hazard caused by the exposure to low levels of FA, as far as its carcinogenic potential by oral route is concerned per se or regarding its use as a food additive. Based on the evidence that FA is formed naturally in food and is a normal mammalian metabolite and that a threshold for carcinogenicity exists both after exposure by inhalation and oral administration, it may be deduced that FA is not carcinogenic at low levels of exposure.

Toxicological evaluation of sicklepod and black nightshade seeds in short-term feeding studies in rats

Nutritionally complete diets containing sicklepod or black nightshade seed at 1, 2, 4, 8, 16 and 32% were fed to groups of three to five male Sprague-Dawley rats in a series of short-term (8–9 days) toxicity studies. Gross clinical observations, body weights and feed and water intake data were recorded. Clinical chemistry analyses, haematology, histology and bone-marrow evaluation for evidence of clastogenic effects were performed. In addition, groups of five female rats were fed sicklepod seed at the same dosages to compare effects on body weight and feed and water consumption. For sicklepod, all of the animals fed diet containing 32% seed and one (female) fed diet containing 16% seed died by day 8. Body-weight gain and feed and water consumption were decreased with increasing doses of sicklepod seed. Other effects of sicklepod seed included: testicular hypospermia at dosages of 8% or greater; and bone-marrow depletion, reduced numbers of polychromatic erythrocytes in the bone marrow, increased neutrophil:lymphocyte ratio, and red nasal discharge at 16%. Black nightshade seed was relatively non-toxic compared with the sicklepod. The principal adverse effects of black nightshade were decreased body-weight gain and feed consumption, which occurred during the first 3 days of the study in animals fed 32% seed.

Practical Application of Microcapsulation for Toxicity Studies Using Bromodichloromethane as a Model Compound

Gelatin-starch syrup (food grade) microcapsulation was applied for toxicology studies of bromodichloromethane (BDCM). BDCM concentrations were stable for 120 days in the microcapsules and for 9 months when incorporated in the powder diet. BDCM concentration in the blood following the administration of microcapsules in olive oil suspension was retained at higher levels than when BDCM was administered as olive oil solution. Subsequently, the microcapsules were mixed in powder diet and were given at concentrations of microcapsulated BDCM of 0, 0.024, 0.072, and 0.215% to groups of 7 male Wistar rats for 1 month. For comparison, BDCM dissolved in olive oil was administered by gavage to groups of 7 male rats for 1 month at dosage levels adjusted to those in the feeding study (0, 20, 60, and 180 mg/kg body weight). Suppression of body weight gain was seen in the high-dosage groups in both the feeding and the gavage studies and was more severe in the former. Similar histopathologic lesions in the liver were shown in both studies, including vacuolization, swelling, and single necrosis of liver cells. Hepatic cord irregularity and bile duct proliferation were observed in the feeding study but not the gavage study. Serum biochemical changes, such as decreases in glucose, triglyceride, and cholinesterase levels, which reflected the histopathologic findings in the liver, were also observed in both studies. Accordingly, the microcapsulation process was proved to pose no qualitative toxic effects on toxicity of BDCM in short-term toxicity studies. It is concluded that the application of microcapsulation is useful for toxicity tests of volatile chemicals when incorporated into food.

Short term toxicity study in rats dosed with isoeugenol benzyl ether.

Isoeugenol benzyl ether was given to rats by gavage for 28 days at 0, 60, 120, and 240 mg/kg body weight/day. For both sexes at the highest dose and females at the intermediate dose statistically significantly decreased values were found for body weight, blood glucose (also for males at intermediate dose), blood urea and relative liver weights. No dose-related histopathological changes were seen in any organs. The no effect level was 60 mg/kg body weight/day.

Effects of salicylate on rat liver in short-term toxicity studies

Effects of salicylate on rat liver in short-term toxicity studies

Results of a short-term toxicity study for three organic chemicals found in Niagara River drinking water.

During the past decade concern has been raised over the quality of drinking water in the communities that draw their supply directly from the Niagara River, which is known to be contaminated with a number of chemical pollutants. At the present, attention is focused on trace organic chemicals in the Niagara River and in Lake Ontario. These substances originate directly from municipal and industrial discharges and indirectly from major waste disposal sites along the river. Dibromomethane, hexanal and tetrahydrofuran among other chemicals were detected in treated drinking water at levels ranging from 0.2-0.8 ..mu..g/L in the Niagara River area. There are no toxicity data available on these chemicals when they are administered to laboratory animals in drinking water. Since the mode of administration may affect the pharmacokinetic behavior and hence the toxic effects of these compounds, it was considered that further animal studies were needed for the regulatory agencies to assess the potential adverse effects in humans associated with the ingestion of the organic chemicals via drinking water. To this end short-term toxicity studies (4 weeks) on dibromomethane, hexanal, and tetrahydrofuran in the rat were carried out.

Local reactions of the saponin Quil A and a Quil A containing iscom measles vaccine after intramuscular injection of rats: A comparison with the effect of DPT-polio vaccine

A short-term toxicity study was performed to investigate local reactions and hematological changes after im injection of Quillaia A (Quil A; 50 or 600 μg/ml) an essential component of an immunostimulating complex (iscom), a novel form of a subunit vaccine, and of iscom measles vaccine containing 360 μg Quil A/ml. The effects were compared with those caused by a sterile phosphate-buffered saline solution and by diphtheria-pertussis-tetanus-polio (DPT-polio) vaccine. Groups of six male rats were injected im with 0.25 ml of the test solution: on Day 0 in the left and on Day 7 in the right musculus gastrocnemius. On Day 14 the animals were killed, and the left and right inguinal lymph nodes were weighed. These organs and the left and right musculus gastrocnemius were investigated microscopically. The only hematological changes observed occurred in the group injected with DPT-polio vaccine: a decrease in the Hb value and in the number of erythrocytes and an increase in mean corpuscular hemoglobin content and in the number of leucocytes. The weights of the left and right inguinal lymph nodes were significantly increased in rats injected with DPT-polio vaccine, iscom measles vaccine, and the high dose of Quil A. The most intense granulomatous inflammatory reaction, mainly consisting of activated macrophages, was observed at the injection sites of all animals of the DPT-polio group. Only one animal injected with the iscom measles vaccine showed a moderate inflammatory reaction of the same type. The regional lymph nodes in all animals of both vaccine groups were activated, indicating a good immune response. Quil A in the highest concentration caused in all animals a different type of inflammatory reaction, characterized mainly by a proliferation of fibroblasts. The low-concentration Quil A revealed an inflammatory reaction only in one animal. Considering the absence of local and hematological effects it can be concluded that there are no objections against the use of Quil A in an iscom vaccine at a concentration of 50 μg/ml vaccine.

Short-term toxicity study of Green S in rats

Groups of 15 rats of each sex were fed Green S at dietary concentrations to provide dose levels of 0 (control), 250, 500 or 1500 mg/kg body weight/day for 13 wk. Additional groups of five animals of each sex were given the same treatments for 2 or 6 wk. There was a marked excretion of green colour in the faeces and some green colouring of the urine, although the latter may have been due to contamination. The males showed increased water and food intakes associated, particularly at the highest dose, with a higher rate of body-weight gain. Haematological examination revealed a transitory mild anaemia at the highest dose level, whilst no findings indicative of a toxic effect were found in the renal concentration tests or the serum analyses. With a dose of 1500 mg Green S/kg a greater proportion of the rats showed higher urinary protein, protein casts, increased caecal weight, thyroid degeneration in female animals and enlargement of the lymph nodes in the intestine wall. The no-effect dose level for Green S in this study was considered to be 500 mg/kg.

Sub-chronic toxicity of methyl benzimidazole carbamate in rats.

Methyl benzimidazole carbamate (MBC) is a broad spectrum systemic fungicide effectively used against a wide variety of pests of vegetable crops and fruit orchards. On seed treatment MBC was found to be actively absorbed by the seedlings and transported to aerial parts. The residual activity of the chemical on various parts of vegetable and food crops was reported to vary from 3.5 to 6.3 ppm persisting from 15 days to 45 days in different parts of the plant. However, WHO has recommended the desirability of conducting short-term and long-term toxicity studies of this fungicide in mammals. Subsequent studies revealed its embryotoxic potential in rats and rabbits. This paper gives the results of sub-chronic administration of MBC in rats designed to assay the possible toxicity to vital organs like the haemopoetic system, liver and kidneys.

Short-term toxicity study in rats dosed with menthone

Menthone, a component of peppermint oil, was given p.o. to groups of 10 male and 10 female rats at dose levels of 0, 200, 400 and 800 mg/kg b.w./day, respectively, for 28 days. After 19 days the dose was reduced to 400 mg/kg b.w. in the female group receiving the highest dose. Analyses of plasma showed a dose-dependent decrease in creatinine content and a dose-dependent increase in alkaline phosphatase activity and bilirubin. The relative weights of liver and spleen were increased. Cyst-like spaces were seen histopathologically in the white matter of the cerebellum of the two highest dose groups. The no-effect level for menthone in this study was lower than 200 mg/kg b.w./day.

Short-term toxicity study of 4-dimethylaminoazobenzene in marmosets.

The marmoset, a small non-human primate, has rarely been used in toxicological studies. A short-term toxicity study was performed on common marmosets (BW = 330 +/- 32 g). Fifteen male marmosets received oral administration of DAB at a dose level of 56 mg/kg/day and 4 control animals received corn oil alone for a period of 15 days. Hematological, biochemical, histopathological and bone marrow examinations were carried out on the 5th, 10th and 15th day of treatment. Body weight decreased continuously and two animals died on day 10. Decreases in RBC, Hb and Ht and increases in MCV and WBC were observed. Uric acid and glucose were increased and AlP and LAP were decreased. Aldolase, GOT and GPT were increased by day 10, and thereafter recovery of aldolase to the control level and decreases of GOT and GPT were observed. Relative organ weights of the liver, kidney, spleen and adrenal were increased. Histologically, C-cell hyperplasia of the thyroid and slight changes of the liver were noted. Marrow total cell counts were not changed, but the G/E ratio was reduced. Thus, macrocytic anemia, an increase of marrow erythroblasts due to anemia and changes of biochemical parameters indicating liver injury were observed in marmosets; these findings were similar to those in rats in the previous experiments.

Safety assessments of chemicals with thresholded effects

Toxicological evaluation of chemicals with thresholded effects involves the estimation of their acceptable daily intakes (ADI). The following steps are involved in the evaluation: judging the completeness of the available chemical and biological data, determination of the no-effect level (NEL), selection of an appropriate safety factor, and extrapolation of the NEL to the ADI using the selected safety factor. The relative insignificance of the sample size on the NEL, the advantages of body weight (compared to the body surface) as a basis for interspecies extrapolation, the size of the safety factor as a function of the nature of the toxic effects, and the multiplicity of the toxicological investigations, in addition to the conventional short-term and long-term toxicity studies, are described. In addition, the possible inadvisability of overemphasizing the importance of dose-response relationship at the expense of in-depth, relevant studies is discussed.

Short-term (6-week) oral toxicity study of selenium in Syrian hamsters

The subacute toxicity of selenium was tested by feeding sodium selenite to Syrian hamsters at dietary levels of 0.1, 1, 5, 10 and 20 ppm selenium for 42 days. General health, survival and organ weights were not adversely affected at any of the dose levels. Weight gain and food intake were relatively low in males fed the highest dose level. The differences from the control values were not statistically significant and there was no similar effect in females. Hamsters fed 10 or 20 ppm retained considerably higher levels of selenium in the liver than did the controls. Microscopic examination of the liver revealed degenerative changes in males and females in the 20-ppm group. The no-toxic-effect level of selenium fed in the diet for 42 days to Syrian hamsters was found to be 10 ppm, equivalent to an intake of about 0.7 mg selenium/kg body weight/day.