2,2'-[6-(4-methoxyphenyl)-1,3,5-triazine-2,4-diyl]bis{5-[(2-ethylhexyl)oxy]phenol}

Endpoint summary

Description of key information

90 day NOAEL (Oral, rat): >= 1000 mg/kg bw 
90 day NOAEL (Dermal, rat): >= 1000 mg/kg bw

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

chronic

Species:

rat

Additional information

Oral:

In the key study for oral repeated dose toxicity, i.e. a subchronic toxicity study acc. to OECD TG 408), Bemotrizinol was administered orally by gavage to Wistar rats of both sexes at dose levels of 100, 500 or 1000 mg/kg body weight/day, daily for a period of at least 92 days (RCC 667541; 1998). Each group comprised 20 animals per sex. A similarly constituted group received the vehicle only and served as a control. Mortality/viability, clinical signs, food consumption and body weights were recorded periodically during the acclimatization and treatment period. Ophthalmoscopic examinations were performed during acclimatization and in the last week of the treatment period (control and high dose animals only). A functional observational battery including an evaluation of hind- and forelimb grip strength was performed during pretest and at weeks 6 and 12. At weeks 5, 9 and 13, blood samples were withdrawn from 10 rats per sex and group for hematology and clinical biochemistry analyses, and urine samples were collected for urinalysis. All animals were killed, necropsied and examined post mortem after at least 92 days of treatment. The weights of the adrenals, brain, kidneys, liver, spleen, testes, thyroid and thymus were recorded. Organs and tissues from all animals of any groups, as well as gross lesions from all animals, were processed as hematoxylin and eosin stained slides and examined by light microscopy.

The oral administration of Bemotrizinol to Wistar rats at doses of 100, 500 or 1000 mg/kg/day, for at least 92 days, resulted in no evidence, either on the in-life or pathomorphologic parameters, of toxic effects of the test article. In particular, no adverse effect on the immune system was recorded and there was no evidence of any neurotoxic effect of Bemotrizinol. The few changes noted in clinical biochemistry and urinalysis parameters were considered to be typical findings within the range of biological variation and the historical control data. Based on the results of this study, the no-observed-effect-level (NOEL) for Bemotrizinol was defined as 1000 mg/kg. 

 

Dermal

In the key study for dermal repeated dose toxicity, i.e. a subchronic toxicity study acc. to OECD TG 411), four treated groups of 13 male and 13 female Wistar Han rats (including three satellite males and three satellite females) received Bemotrizinol daily by cutaneous application at the dose-levels of 250, 500, 1000 (without protective collar) or 1000 mg/kg/day (with protective collar) for 13 weeks (CIT 25378, 2004). An additional group of 10 males and 10 females received the vehicle alone (polyethylene glycol 400) under the same experimental conditions and acted as a control group. Animals of the second high-dose group (given 1000 mg/kg/day) wore a protective plastic collar over at least a 6-hour period after each application. After the exposure period, the application site of these animals was cleaned with tap water and dried with absorbent paper. The animals were checked daily for mortality and clinical signs. Detailed clinical examinations were performed before the beginning of the treatment period and then once a week. Body weight and food consumption were recorded once a week during the study. Neurotoxic evaluation using functional observation battery (FOB) was carried out at the end of the treatment period on animals of the vehicle control and high-dose groups (without collar). Ophthalmological examinations were performed on animals of the vehicle control and high-dose groups (without collar). The estrous cycle stage was determined for 14 consecutive days during weeks 11 and 12 for each female. Hematology, blood biochemical investigations and urinalysis were performed at the end of the treatment period. Satellite animals were allocated for the determination of the test item plasma levels and were sampled prior to dosing, on day 8 and weeks 6 and 13. On completion of the treatment period, the animals were killed and submitted to a full macroscopic post-mortem examination. Designated organs were weighed and selected tissue specimens were preserved. A microscopic examination was performed on selected tissues from animals of the vehicle control and the two high-dose groups and on all macroscopic lesions in the low- and mid-dose groups.

No clinical signs, hematological, blood biochemical, urinary or histopathological findings were observed at any dose-level. Plasma levels indicated that the test item was not bioavailable. Consequently, under the experimental conditions of the study, the No Observed Effect Level (NOEL) of the test item is 1000 mg/kg/day.

In support, in a dermal carcinogenicity study in Wistar rats (acc. to OECD TG 451), three test-treated groups of 100 Wistar Han rats (50 males and 50 females) received Bemotrizinol at 100, 500 or 1000 mg/kg/day by daily cutaneous application for 104 weeks (CIT 25382; 2006). Another group of 50 males and 50 females received no treatment and acted as an untreated control group. An additional group of 50 males and 50 females received the vehicle alone (polyethylene glycol 400) under the same experimental conditions and acted as vehicle control group. The animals were checked daily for mortality, clinical signs and possible signs of skin irritation. The animals were palpated every 2 weeks after 6 months of treatment in order to monitor the onset and progression of any masses. Body weight and food consumption were recorded at designated intervals (weekly during the first 3 months of treatment and then monthly). Ophthalmological examinations were performed on all the animals before the beginning of the treatment period and on 10 animals/sex in the vehicle control and high-dose groups in weeks 26, 52, 78 and 103. The differential white cell count was determined in weeks 52 and 78 for the animals in the vehicle control and high-dose groups. Blood samples for the determination of plasma levels of the test item were taken in weeks 13, 26, 52, 78 and 104. On completion of the treatment period, blood samples were taken from 10 animals/sex and group for hematology and blood biochemistry investigations. All surviving animals were euthanized and submitted to a macroscopic post-mortem examination. Designated organs and any masses or lesions were sampled from each animal and retained for microscopic examination.

The survival rate was not affected by treatment with Bemotrizinol. There were no clinical signs and no effects on body weight or food consumption at any dose-level. At laboratory investigations, no differences among hematological and blood biochemical parameters were attributed to treatment with Bemotrizinol. The systemic exposure seemed similar among the test item treated groups whatever the dose-level applied. Bemotrizinol induced dose-related non-neoplastic skin lesions at the treated skin from 100 mg/kg/day. The pattern of changes was indicative of chronic moderate skin irritation. No other non-neoplastic or neoplastic organ changes were attributed to treatment with Bemotrizinol. Overall, the daily treatment with Bemotrizinol for 104 weeks induced only non-neoplastic findings at the treated skin area indicative of a chronic and moderate local skin irritation.

In a supportive study following daily cutaneous application to Göttingen minipigs for 39 weeks, three groups of four male and four female minipigs received a daily renewed cutaneous application of Bemotrizinol as a suspension in polyethylene glycol 400, on closely clipped dorsal skin (10% of the body surface area), at the dose-levels of 250, 500 or 1250 mg/kg/day (the highest technically achievable dose-level; CIT 25384TCN, 2006). A fourth group, of four males and four females, received the vehicle alone at a constant dosage volume of 2.5 mL/kg under the same experimental conditions and served as a control group.

Bemotrizinol was clinically well tolerated. No local or systemic toxic effects or target organs were identified at any dose-level. Although Bemotrizinol was detected in the plasma of all the animals, their systemic exposure was minimal, as the Bemotrizinol plasma concentrations were lower than 10 ng/mL in most animals. Consequently, under the experimental conditions of this study, the No Observed Effect Level (NOEL) is considered to be higher than 1250 mg/kg/day. 

 

In another supportive study, the local tolerance after repeated cutaneous applications of Bemotrizinol for 2 weeks at concentrations of 3% and 10% was evaluated in Hartley guinea pigs (CIT 23972TSG; 2002). Bemotrizinol was prepared at the concentrations of 3% and 10% in diethoxyethyl succinate. The dosage form preparations were applied open once daily to each animal, at approximately the same time each day, five days a week for a 2-week period. Cutaneous reactions (erythema, oedema and desquamation) were evaluated on both flanks of each animal before each application and on day 15.

Under the chosen experimental conditions, repeated cutaneous applications of Bemotrizinol to guinea pigs resulted in scoring indices of 1.0, 0.3 and 0.0 at the concentrations of 10%, 3% and 0% (vehicle), respectively. The skin effects observed included slight to well defined erythema and  slight desquamation. Except for 1 animal, showing a slight desquamation and erythema at day 15, all skin effects were transient and reversible after prolonged application.

Justification for classification or non-classification

The present data on repeated dose toxicity do not fulfill the criteria laid down in 67/548/EEC and regulation (EU) 1272/2008, and therefore, a non-classification is warranted.