In vivo mutagenicity assessment of orally treated tert-butyl hydroperoxide in the liver and glandular stomach of MutaMouse.

BACKGROUND: tert-Butyl hydroperoxide (TBHP; CAS 75-91-2), a hydroperoxide, is mainly used as a polymerization initiator to produce polyethylene, polyvinyl chloride, and unsaturated polyester. It is a high-production chemical, widely used in industrial countries, including Japan. TBHP is also used as an additive for the manufacturing of food utensils, containers, and packaging (UCP). Therefore, there could be consumer exposure through oral intake of TBHP eluted from UCPs. TBHP was investigated in various in vitro and in vivo genotoxicity assays. In Ames tests, some positive results were reported with and/or without metabolic activation. As for the mouse lymphoma assay, the positive result was reported, regardless of the presence or absence of metabolic activation enzymes. The results of some chromosomal aberrations test and comet assay in vitro also demonstrated the genotoxic positive results. On the other hand, in in vivo tests, there are negative results in the bone marrow micronucleus test of TBHP-administered mice by single intravenous injection and the bone marrow chromosomal aberration test using rats exposed to TBHP for 5 days by inhalation. Also, about dominant lethal tests, the genotoxic positive results appeared. In contrast, there is little information about in vivo mutagenicity and no information about carcinogenicity by oral exposure. RESULTS: We conducted in vivo gene mutation assay using MutaMice according to the OECD Guidelines for the Testing of Chemicals No. 488 to investigate in vivo mutagenicity of TBHP through oral exposure. After repeated dosing for 28 days, there were no significant differences in the mutant frequencies (MFs) of the liver and glandular stomach up to 300 mg/kg/day (close to the maximum tolerable dose (MTD)). The positive and negative controls produced the expected responses. CONCLUSIONS: These findings show that orally administrated TBHP is not mutagenic in the mouse liver and glandular stomach under these experimental conditions.

In vivo mutagenicity assessment of styrene in MutaMouse liver and lung.

BACKGROUND: Styrene (CAS 100-42-5) is widely used as polystyrene and acrylonitrile-butadiene-styrene resin such as plastic, rubber, and paint. One of the primary uses of styrene is food utensils and containers, but a small amount of styrene transferred into food can be ingested by eating. Styrene is metabolized into styrene 7,8-oxide (SO). SO is mutagenic in bacteria and mouse lymphoma assays. It is clastogenic in cultured mammalian cells. However, styrene and SO are not clastogenic/aneugenic in rodents, and no rodent in vivo gene mutation studies were identified. METHODS: To investigate the mutagenicity of orally administered styrene, we used the transgenic rodent gene mutation assay to perform an in vivo mutagenicity test (OECD TG488). The transgenic MutaMouse was given styrene orally at doses of 0 (corn oil; negative control), 75, 150, and 300 mg/kg/day for 28 days, and mutant frequencies (MFs) were determined using the lacZ assay in the liver and lung (five male mice/group). RESULTS: There were no significant differences in the MFs of the liver and lung up to 300 mg/kg/day (close to maximum tolerable dose (MTD)), when one animal with extremely high MFs that were attributed to an incidental clonal mutation was omitted. Positive and negative controls produced the expected results. CONCLUSIONS: These findings show that styrene is not mutagenic in the liver and lung of MutaMouse under this experimental condition.

Initial hazard assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate: Genotoxicity tests and combined repeated-dose and reproductive/developmental toxicity screening in rats.

Ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate, used in laundry detergents, shampoos, and body soaps, is classified by the Japanese Chemical Substances Control Law as a priority assessment chemical substance for environmental effects. However, its toxicity data for human health are insufficient. This study evaluated this chemical under the Safety Examination of Existing Chemicals and Safety Programmes of the Ministry of Health, Labour and Welfare (MHLW). The MHLW conducted bacterial reverse mutation (Ames test), in vitro chromosomal aberration, and combined repeated-dose and reproductive/developmental toxicity screening tests. We performed a screening assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate for human health. The chemical showed a negative reaction in the Ames test and a positive reaction in the in vitro chromosomal aberration test with metabolic activation in rats. The combined repeated-dose and reproductive/developmental toxicity screening test showed significantly decreased food consumption at 50 mg/kg body weight/day, but no reproductive and developmental toxicity was observed. The no-observed-effect level of 15 mg/kg/day was obtained as a screening value. Therefore, this chemical was classified as hazard class 3, with a derived-no-effect level of 0.025 mg/kg/day. The results of this study will be useful for risk assessment of groups of structurally similar alkyl quaternary ammonium surfactants.

Initial hazard assessment of benzyl salicylate: In vitro genotoxicity test and combined repeated-dose and reproductive/developmental toxicity screening test in rats.

Benzyl salicylate is used as a fragrance ingredient and an ultraviolet light absorber, but its toxicity is unknown. Therefore, toxicity tests and hazard classification were conducted for screening assessment under the Japanese Chemical Substances Control Law. Benzyl salicylate was found to be non-genotoxic in vitro based on the chromosomal aberration test using Chinese hamster lung cells. However, the combined repeated-dose and reproductive/developmental screening toxicity test, in which male and female rats were administered benzyl salicylate by gavage at 0, 30, 100, or 300 mg/kg/day for 42 and 41-46 days, respectively, from 14 days before mating until postnatal Day 4, showed that repeated doses had major effects on the thymus, liver, epididymis, and femur at 100 and/or 300 mg/kg/day. Furthermore, although benzyl salicylate had no effect on the estrus cycle, fertility, corpus lutea, or implantation rate, embryonic resorption, offspring mortality, and neural tube defects were observed at 300 mg/kg/day, and the offspring had lower body weights at 30 and 100 mg/kg/day, suggesting teratogenicity similar to other salicylates. Based on the developmental toxicity, this chemical was classified as hazard class 2, with a lowest observed adverse effect level (LOAEL) of 30 mg/kg/day and a D-value of 0.003 mg/kg/day.

Initial hazard assessment of 4-benzylphenol, a structural analog of bisphenol F: Genotoxicity tests in vitro and a 28-day repeated-dose toxicity study in rats.

4-Benzylphenol (CAS No. 101-53-1), a structural analog of bisphenol F, has estrogenic activity in vitro and in vivo, as is the case with bisphenol F. 4-Benzylphenol is used in plastics and during organic synthesis. Since its safety is largely unknown, we conducted toxicity tests as part of screening risk assessment in an existing chemical safety survey program. Based on results of the Ames test and the chromosomal aberration test using Chinese hamster lung cells (OECD TG 471 and 473), 4-benzylphenol was determined to be non-genotoxic in vitro. In a 28-day repeated-dose toxicity study, Crl:CD (SD) rats were administrated 4-benzylphenol by gavage at 0, 30, 150, or 750 mg/kg/day (OECD TG 407). Consequently, body weight was lower in males at 750 mg/kg/day. In the liver, relative organ weights were increased in both sexes at 750 mg/kg/day, and centrilobular hepatocellular hypertrophy was observed in males at 150 and 750 mg/kg/day. In the forestomach, hyperkeratosis and hyperplasia of squamous cells were observed in males at 150 and 750 mg/kg/day, and in females at 750 mg/kg/day. Based on these results, we identified the NOAEL for 4-benzylphenol as 30 mg/kg/day, with a hazard assessment value (D-value) of 0.05 mg/kg/day corresponding to hazard class 3.