Methoxycarbonyloxycyclooct-4-ene

Endpoint summary

Description of key information

The NOAEL for repeated dose toxicity is set to 500 mg/kg bw based on acute and all repeated dose toxicity information. 

Several studies are used to derive a NOAEL for repeated dose toxicity. Based on the acute oral toxicity study (LC50 2400 mg/kg bw) the highest dose selected in the 28-day gavage OECD TG 407 was 500 mg/kg bw at which no adverse effects were seen.

Dietary dosing was selected for the next studies (DRF for OECD TG 421 and OECD TG 421) because peak exposure are prevented as well as potential acidic/irritation due to ester (carboxylate) cleavage. The highest dose in the 14-day DRF for the Reproscreen study was 1000 mg/kg bw (15000 ppm) nominal. At this dose food consumption and body weight were reduced (probably due to palatability). Also high increased relative liver weight especially in males was seen (+48%). Therefore the highest dose tested in the Reproscreen study is  500 mg/kg bw (7500 ppm) in which no adverse repeated dose toxicity was seen. Therefore the NOAEL is set to 500 mg/kg bw based on acute oral toxicity at 2000 mg/kg bw (2 females died) and based on highly increased liver weight at 1000 mg/kg bw (+48%) in the DRF for the OECD TG 421.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

subacute

Experimental exposure time per week (hours/week):

168

Species:

rat

Organ:

kidney

liver

Additional information

As presented above all studies are used to derive the NOAEL for systemic toxicity. The executive summaries are presented below. The study records of the dose range finder of the OECD 421 and the OECD 421 can be found in the 'toxicity to reproduction' section.

Violiff – Repeated dose - OECD TG 407

Violiff was tested in a 28-day oral repeated dose toxicity study comparable to the OECD TG 407, according to GLP principles with rats. Five male and five female rats were orally exposed to the substance at 0, 20, 100 and 500 mg/kg bw/ day. The doses were selected based on the acute oral toxicity study with the lowest LD50 for females at 2400 mg/kg bw and 2 females were dead at 2000 mg/kg bw.

Results: No treatment-related clinical effects were seen, no effects were detected on body weight gain or food consumption. No treatment related effects were seen on haematology in males and females. In males slight decreases in WBC counts were seen (ca 20%) which were not dose related and not considered to be toxicologically relevant. No adverse effects on biochemistry were seen. The slight decrease in GPT and GOT, which parameters can be related to e.g. liver function, are not considered to toxicologically relevant because increases may be indicative of concern but not decreases.

Organ and related effects: In males and females there were no or minimal effects on liver, kidney, and adrenal weights, macroscopic or microscopic effects. In males no effects on testes was seen and in females there were no effects on ovaries. In males moderate cortical tubular epithelial eosinophilic inclusions were observed in the kidneys of all male rats receiving 500 mg/kg/day and minimal eosinophilic inclusions in all males receiving 100 mg/kg/day and 20 mg/kg/day. However, since eosinophilic inclusions in the kidney are considered to be related to light hydrocarbon nephropathy which is specific for the male rat this effect will not be considered for deriving the NOAEL for humans. The NOAEL is set at 500 mg/kg bw/day  the highest dose tested because the effects seen are considered minimal, adaptive in nature and/or not relevant for humans.

Violiff – 14d DRF for OECD TG 421

A 14-day range-finding study in the diet was performed to select the dose levels for a subsequent oral (diet) reproduction toxicity screening study (OECD 421) with the test substance in rats. Diet was chosen to prevent potential acidic/irritating effects due to ester cleavage. Four male and female rats were administered different dose levels of the test substance in the diet for 14 subsequent days. Test diets with concentrations of 0, 20, 100, 500 and 1000 mg/kg bw nominal (equivalent to 300, 1500, 7500 and 15000 mg/kg diet) were prepared shortly before the start of the study and stored in daily portions in a ≤ -18 °C freezer. The food was refreshed daily. In-life parameters included, mortality, clinical observations, body weight and food consumption. For the females the estrous cycle was measured. At sacrifice animals were examined for gross anatomical changes, and terminal body weight, liver weight and kidney weight were determined. For the males sperm parameters were measured. From all animals urine and blood was collected. For the males and females of the high dose group and top dose group blood and urine were analysed for carboxylic acid concentrations as potential acid formation was considered.

Results: No mortalities and no clinical signs were observed in all dose groups. A markedly reduced feed consumption and reduced body weight in males and females of the high dose and top dose groups for the first days after the start of exposure was observed. This was related to the palatability of the test substance. The final body weights at the top dose were decreased but < 10%.

Organ related findings: An increased dose related (relative) liver weight in males of the mid dose, high dose and top dose group was seen up to 48%. In females in the top dose relative liver weight was increased with 18% at the top dose. Increased (relative) kidney weight in males from the high dose and top dose groups was reported up to 19%. No effects were found on the estrus cycle and on testicular or epididymal sperm counts or motility. The urinary pH ranged from 6.79 to 7.20 and no treatment related effects were observed. The test item concentration did not decrease in the diets from 1 day to 6 days in the animal room. The test substance was not homogeneously distributed in the diets. No carboxylic acid was observed in plasma however carboxylic acid was observed in the urine. The carboxylic acid levels in urine samples from the high dose and top dose animals showed large inter-individual differences. Based on the effects observed in food consumption and body weight of the high dose and top dose animals as well as the high increased liver and kidney weights in males the 500 mg/kg bw (7500 ppm) is proposed as a high dose level in the subsequent reproduction toxicity screening test. No effects were observed in the low dose group and minimal effects in the mid dose group. Based on the absence of effects, 100 mg/kg bw (1500 ppm) is proposed as a low dose level in the subsequent reproduction toxicity screening test.

Violiff – Reproscreen study – OECD TG 421

In an OECD 421 guideline study performed in compliance with GLP, male and female Wistar rats were exposed to the test substance via the diet at nominal mg/kg bw doses of 100 (1500 ppm), 300 (5000 ppm) or 500 (7500 ppm). The doses in the diet were selected based on the 14-day DRF. Exposure to the substance covered a premating period of 2 weeks, during mating (1 week), gestation and lactation until postnatal day 4. In life parameters included clinical observations, body weight, and food consumption. At necropsy animals were macroscopically examined, liver and kidney weight were recorded. Male (testes, epididymides, seminal vesicles and prostate) and female (ovaries and uterus) reproductive organs, kidneys and livers were examined microscopically.

Results: Analysis: The test item was considered to be homogeneously distributed in the diets. The results of the stability experiments showed that the test item was not stable in the diets at ambient temperature in the animal room. Relative decreased of the test item concentration were 29%, 24% and 22% after seven days for the low dose, mid dose and high dose groups, respectively. Analysis for test item content of the diets showed that the concentration of the test item in the diets was close to intended.

Clinical signs: No mortality or morbidity was observed during the study. Statistically significantly decreased body weight gains during the first week of treatment in males and females in the high dose group was seen. This was accompanied with statistically significantly reduced food consumption during the first week of treatment in males and females in the mid dose and high dose group as compared to the control group. These effects were related to palatability of the test substance and not considered adverse.

Organ weights: Statistically significantly increased mean relative liver weight in males of the high and mid dose: +23 and +15%, respectively not accompanied by microscopic abnormalities. Statistically significantly dose related increased relative kidney weights in males of all test item-treated groups were observed (+16% in the high dose. These were related to alpha-2u-globulin nephropathy (confirmed by immune staining) and therefore not considered adverse for humans. No effects in females were seen on these organs.

Fertility: Finally, no effects on organ weight, macroscopical or microscopical examination of the reproductive organs were observed. No effects on mating index, fertility index, pregnancy rates, gestation index or days. No effects on number of corpora lutea, implantation sites or preimplantation loss.

Conclusion: Based on the absence of adverse effects in males and females the NOAEL for parental toxicity was established at 500 mg/kg bw (nominal) corresponding to a dose of at least 332 mg/kg body weight per day for males and at least 378 mg/kg body weight for females.

Justification for classification or non-classification

Based on the results of a sub-acute repeated dose study and a reproduction/developmental toxicity screening test the substance does not have to be classified for repeated dose toxicity in accordance with Regulation (EC) No. 1272/2008.