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

Assessing the Safety of Mechanically Fibrillated Cellulose Nanofibers (fib-CNF) via Toxicity Tests on Mice: Single Intratracheal Administration and 28 Days' Oral Intake

Mechanically fibrillated cellulose nanofibers, known as fib-CNF (fiber length: 500 nm; diameter: 45 nm), are used in composites and as a natural thickener in foods. To evaluate their safety, we conducted a 28-day study in mice with inhalation exposure at 0.2 mg/body and oral administration of 400 mg/kg/day. Inhalation exposure to fib-CNF caused transient weight loss, changes in blood cell counts, and increased lung weights. These changes were attributed to adaptive responses. The oral administration of fib-CNF for 28 days resulted in no apparent toxic effects except for a slight decrease in platelet counts. The fib-CNF administration using the protocols studied appears to be safe in mice.

Single and Repeated Oral Dose Toxicity and Genotoxicity of the Leaves of Butterbur

Butterbur (Petasites japonicus (Siebold & Zucc.) Maxim) leaves are available to consumers in the marketplace, but there is no guarantee that they are safe for human consumption. Previously, we demonstrated that hot water extracts of P. japonicus leaves (KP-1) had anti-inflammatory properties and attenuated memory impairment. However, data regarding KP-1 toxicity are lacking. This study assessed the safety of KP-1 by examining oral and genotoxic effects using in vivo and in vitro tests, respectively. In a single oral dose toxicity and two-week repeated oral dose toxicity study, we observed no toxicologically significant clinical signs or changes in hematology, blood chemistry, and organ weights at any dose during the experiment. Following a thirteen-week repeated oral dose, toxicity, hyperkeratosis, and squamous cell hyperplasia of the limiting ridge in the stomach were observed. The no observable adverse effect level (NOAEL) was found to be 1250 mg/kg/day in male and female rats. However, hyperkeratosis and hyperplasia were not considered to be of toxicological significance when extrapolating the NOAEL to humans because the limiting ridge in the stomach is species-specific to rats. Therefore, in our study, the NOAEL was considered to be 5000 mg/kg/day when the changes in the stomach’s limiting ridge were discounted. Moreover, in vitro bacterial reverse mutations and chromosomal aberrations in Chinese hamster lung (CHL) cells and the in vivo micronucleus in Institute of cancer research (ICR) mice assays showed that KP-1 possessed no mutagenicity. Although additional research is required, these toxicological evaluations suggest that KP-1 could be safe for human consumption.

Prenatal exposure to bisphenols affects pregnancy outcomes and offspring development in rats

The objective of this study was to evaluate the effects of gestational exposure to low doses of bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF) on pregnancy outcomes and offspring development. Pregnant Sprague-Dawley rats were orally dosed with vehicle, 5 μg/kg body weight (BW)/day of BPA, BPS and BPF, or 1 μg/kg BW/day of BPF on gestational days 6-21. Pregnancy and gestational outcomes, including number of abortions and stillbirths, were monitored. Male and female offspring were subjected to morphometry at birth, followed by pre- and post-weaning body weights, post-weaning food and water intakes, and adult organ weights. Ovarian follicular counts were also obtained from adult female offspring. We observed spontaneous abortions in over 80% of dams exposed to 5 μg/kg of BPF. BPA exposure increased Graafian follicles in female offspring, while BPS and BPF exposure decreased the number of corpora lutea, suggesting reduced ovulation rates. Moreover, BPA exposure increased male kidney and prostate gland weights, BPF decreased epididymal adipose tissue weights, and BPS had modest effects on male abdominal adipose tissue weights. Prenatal BPS exposure reduced anogenital distance (AGD) in male offspring, suggesting possible feminization, whereas both BPS and BPA induced oxidative stress in the testes. These results indicate that prenatal exposure to BPF affects pregnancy outcomes, BPS alters male AGD, and all three bisphenols alter certain organ weights in male offspring and ovarian function in female offspring. Altogether, it appears that prenatal exposure to BPA or its analogues can induce reproductive toxicity even at low doses.

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.

Effects of prepubertal exposure to forchlorfenuron through prenatal and postnatal gavage administration in developing Sprague-Dawley rats

Forchlorfenuron (CPPU), a plant growth regulator, is widely used in agriculture. However, its long-term exposure effects on humans, especially neonates, remain unclear. Therefore, we investigated the developmental toxicity of prenatal and postnatal gavage administration of CPPU in rats. Pregnant Sprague-Dawley rats were administered 300 mg/kg/day CPPU by gavage from day 6 of gestation to the cessation of nursing. During weaning, rat offspring were administered 0, 30, 100, or 300 mg/kg/day CPPU for 4 weeks, followed by a 4-week CPPU-free recovery period. There were no significant differences in clinical symptoms, body weight, development indicators, serum biochemical parameters, sex hormone levels, sperm motility, relative organ weights, and histopathological changes among the 0-100 mg/kg/day CPPU groups. In the 300 mg/kg/day CPPU group, female rats exhibited decreased body weight, earlier time of vaginal opening (VO) and first estrus time (FE), elevated estradiol and blood urea nitrogen (BUN) levels, and upregulation of estrogen receptor 1 gene expression, whereas male rats only exhibited increases in serum BUN, creatinine, and glucose levels. Most changes were reversed after the recovery period. Furthermore, the endometrial epithelial height was significantly increased in female rats despite the absence of significant changes in uterine wall thickness and endometrial glands. Thus, CPPU may promote estradiol secretion, resulting in altered VO and FE and adverse effects in prepubertal female rats. These findings may be applied for risk assessment following CPPU exposure in humans.

Initial hazard assessment of 1,4-dichlorobutane: Genotoxicity tests, 28-day repeated-dose toxicity test, and reproductive/developmental toxicity screening test in rats

1,4-Dichlorobutane (1,4-DCB) is used as raw materials for drugs, pesticides, fragrances, and chemical fibers, and being used as a solvent. Its toxicity data was insufficient for screening assessment under the Japanese Chemical Substances Control Law. We conducted toxicity tests and hazard classification for screening assessment 1,4-DCB showed negative in the Ames test, positive in the in vitro chromosomal aberrations test with metabolic activation, and negative in the in vivo mouse bone-marrow micronucleus test. The 28-day repeated-dose toxicity study, where male and female rats were administered 1,4-DCB by gavage at 0, 12, 60, and 300 mg/kg/day, showed significant effects on the liver and pancreas from 12 mg/kg/day and kidney at 300 mg/kg/day. Based on periportal hepatocellular hypertrophy and decreased zymogen granules in pancreas, the lowest observed adverse effect level (LOAEL) of 12 mg/kg/day was obtained. The reproductive/developmental toxicity screening study, in which male and female rats were administered 1,4-DCB by gavage at dose of 0, 2.4, 12, and 60 mg/kg/day for 42-46 days, showed that the delivery index was decreased at 60 mg/kg/day without maternal toxicity. Based on the general toxicity, we classified this chemical as hazard class 2, with a D-value (Derived No Effect Level) of 0.002 mg/kg/day.

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.