2-tert-butylcyclohexyl ethyl carbonate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Parental systemic toxicity: NOAEL ≥ 500 mg/kg bw/d

Fertility: NOAEL ≥ 500 mg/kg bw/d (OECD 422, RA, K, Rel.2)

(equivalent to an overall intake of at least 437 mg/kg bw/day in female rats and 505 mg/kg bw/day in male rats)

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The key study is GLP-compliant and of high quality. The study was fully reliable (Klimisch score = 1), however the reliability score was lowered to 2 which is the maximum score for read-across.

Additional information

No study was available on the substance itself. However a key study was identified on the supporting substance (TNO Triskelion, 2012). In this combined oral repeated dose toxicity study and reproductive/developmental toxicity screening test performed in accordance with OECD test guideline No. 422 and in compliance with GLP, 2-tert-butylcyclohexyl acetate was daily administered to Wistar strain rats at doses of 0, 75, 200 or 500 mg/kg bw/day in diet during a premating period of 10 weeks and during mating (1 week), gestation and lactation until postnatal day 4.

Daily clinical observations during the premating, gestation and lactation period did not reveal any treatment-related changes in the animal’s appearance, general condition or behaviour. One animal in the low dose was sacrificed moribund during lactation. Neurobehavioural observations and motor activity assessment did not indicate any neurotoxic potential of the test substance.

A lower body weight and body weight gain was observed in the males of the high dose group. Since the effect on body weight gain was most clear in the first weeks of the study, the effect may be (partly) due to the palatability of the test substance in the diets and, for that reason, considered of marginal toxicological relevance. Also in the female animals of the mid- and high-dose groups, a slightly lower body weight gain was observed in the first week of dosing only. No effects on food consumption were observed for the males. In the females, food consumption was lower in the mid and high dose group during the first week of dosing only.

The mean test substance intake (mg Verdox/kg body weight/day), calculated from the nominal dietary concentration, feed consumption and the body weight was 56 for the males and 52 – 59 for the females of the low dose group, 168 for the males and 151 – 177 for the females of the mid dose group and 505 for the males and 437 – 554 for the females of the high dose group. However, the actual test substance intake was lower since the test substance concentration was not met in the low dose group (-11%) and was not stable in the diet in the mid dose group (-12%). For that reason the actual test substance intake ranged between 50 – 56 for males and 46 – 59 for the females of the low dose group. For the mid dose group the actual test substance concentration ranged from 148 – 168 for the males and 133 – 177 for the females.

No treatment related effects were observed on pre-coital time, mating index, male and female fertility indices, female fecundity index, gestation index, duration of gestation, pre- and postimplantation loss, number of corpora lutea, number of implantation sites and number of pups delivered.

No effects were observed on litter size, pup sex and weight and pup survival.

No treatment-related effects were observed on sperm-parameters (epidydimal sperm motility, sperm count and morphology and testicular sperm count).

At autopsy the males of the high dose group showed an increased relative liver weight. Since no adverse effects were observed on histopathology of the liver and on clinical chemistry parameters the increased liver weight as observed in the male animals is considered as an adaptive response to increased physiological demand and of no toxicological relevance. A dose related increase in relative kidney weight was observed in the mid and high dose males. The increased weight of the kidneys were related to α2u-microglobulin nephropathy (see next paragraph) and considered of no toxicological relevance. No effects on organ weights were observed in females.

The male animals showed a dose-dependent increase of hyalin droplet nephropathy that resembled that of chemically induced α2u-globulin nephropathy. Immunohistochemical staining confirmed the increased accumulation of α2u-globulin in the cortical tubular epithelial cells. The discrepancy between the incidence of hyalin droplet nephropathy observed in the HE stained slides and the incidence of increased α2u-globulin staining was caused by the different approach of the evaluation. In the HE stained slides the kidneys were examined with high magnification necessary to establish the presence of the intracellular hyalin droplets. The immunohisto- chemically stained slides were examined for the presence of α2u-globulin which was done by judging the general positive staining intensity which has to be assessed with low magnification.

The proposed mechanism of hyalin droplet nephropathy is that the test substance or its metabolite(s) bind(s) to the α2u-globulin protein. This protein/chemical complex is filtered at the glomerulus and is reabsorbed into the proximal tubule cells. The binding of the chemical inhibits the lysosomal breakdown of the α2u-globulin and the protein/chemical complex builds up in the lysosomes (hyalin droplets formation). Ultimately the lysosomes rupture and the cells die as a result (eosinophilic debris in the tubular lumen). The α2u-globulin is produced in the liver and androgen controlled, hence not present in female rats. α2u-Globulin nephropathy is a well known phenomenon. It is male rat specific and considered of no toxicological relevance.

In conclusion, based on these results, the no observed adverse effect level (NOAEL) for males and females was:

- 500 mg/kg bw/d (nominal) in male and female rats for sexual function and fertility, corresponding to 505 mg/kg bw/day for males and 437 mg/kg bw/day for females (actual dose received),

- 500 mg/kg bw/d (nominal) for developmental toxicity (foetal and pup growth until Day 4), corresponding to 437 mg/kg bw/day for females (actual dose received

- 500 mmg/kg bw/d (nominal) for the lactation (during 4 days), corresponding to 437 mg/kg bw/day for females (actual dose received).

Conclusion: According to the similar physico-chemical proporties between 2-tert-butylcyclohexyl acetate and 2-tert-butylcyclohexyl carbonate, the registered test substance is considered to have a NOAEL ≥500 mg/kg body weight/d for fertility and developmental toxicity.

Effects on developmental toxicity

Description of key information

A developmental toxicity study is not required at Annex VIII level. As no alerts for reproductive toxicity to were highlighted in the screening study, no additional study is proposed at this tonnage level.

Justification for classification or non-classification

Harmonized classification:

The substance has no harmonized classification according to the Regulation (EC) No 1272/2008 (CLP).

Self-classification:

Based on the available data, no self-classification is proposed regarding the reproductive toxicity after oral dose-repeated exposure according to the Annex VI of the Regulation (EC) No. 1272/2008 (CLP) and to the GHS.

Data lacking for toxicity on or via lactation is proposed based on the criteria of the Regulation (EC) No. 1272/2008 (CLP) and to the GHS. However, few information is available in the reproductive/developmental toxicity screening test where no effect was observed during the period of lactation of 4 days.

No data are available regarding the dermal and inhalation route.