Diethyl carbonate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Diethyl carbonate

EC Number:

203-311-1

EC Name:

Diethyl carbonate

Cas Number:

105-58-8

Molecular formula:

C5H10O3

IUPAC Name:

diethyl carbonate

Test material form:

solid

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Rat, Han: of Wistar origin

Sex:

male/female

Details on test animals or test system and environmental conditions:

The rat is commonly used species for toxicological studies in accordance with international recommendations.
The Wistar rat was the system of choice because it has been the preferred and most commonly used species for oral gavage toxicity tests and is a well-known laboratory model with sufficient historical data.

Administration / exposure

Route of administration:

oral: gavage

Details on route of administration:

The test item was administered orally via gavage.

Vehicle:

vegetable oil

Remarks:

Sunflower oil

Details on oral exposure:

Diethyl carbonate was suspended in the vehicle (sunflower oil) in concentrations of 25, 75 and 250 mg/mL.
Formulations were prepared in the formulation laboratory of the Test Facility beforehand for not longer than 4 days and stored in a refrigerator (5±3 °C) until use.
Table 1 contains the group numbers, doses and concentration of formulations that were administered to the animals.

Table 1: Concentrations used in the study

Groups
Dose
(mg/kg bw/day) Nominal concentration of formulations (mg/mL)
Group 1 0 0
Group 1 R⃰ 0 0
Group 2 100 25
Group 3 300 75
Group 4 1000 250
Group 4 R⃰ 1000 250
⃰ = Recovery

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical control of dosing formulations (verification of concentrations and homogeneity) was performed in the Analytical Laboratory of Test Facility three times during the study.

Duration of treatment / exposure:

90/91 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

control group

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

300 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

15 animals/sex in the control and highest dose groups – including recovery animals – and 10 animals/sex in the low and middle dose groups

Control animals:

yes, concurrent no treatment

Positive control:

without positive control group

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

Diethyl carbonate did not induce clinical signs at 100, 300 or 1000 mg/kg bw/day in male or female animals during the course of the 90/ 91-day administration or the four weeks recovery period.

Mortality:

no mortality observed

Description (incidence):

There was no mortality in the control, 100, 300, or 1000 mg/kg bw/day groups during the 90/91-day treatment (male/ female, respectively) period or during the following 4-week recovery period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

There were no test item related changes in the mean body weight and body weight gain in the male and female animals at 100, 300 and
1000 mg/kg bw/day.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

No adverse effects on the mean food consumption development were observed at 100, 300 or 1000 mg/kg bw/day in male or female animals (main and recovery groups).

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No alterations were detected in the eyes of the animals of the high dose group at the end of treatment or recovery periods.

Haematological findings:

no effects observed

Description (incidence and severity):

There were no test item related adverse pathological changes in the investigated hematological or blood coagulation parameters in any group
(main and recovery groups).

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

Pathological test item effects were not detected upon the evaluation of the clinical chemistry parameters in male or female animals at 100, 300 and 1000 mg/kg
bw/day (main and recovery groups).
In male and female animals at 100, 300 and 1000 mg/kg bw/day the level of FT3 (free T3) and FT4 (free T4) thyroid hormones
were normal at the end of treatment and recovery period. The levels of TSH were below the limit of detection.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

No treatment related alterations were found in the organ weight results (absolute weights, relative to the body weight and brain weight) in male and female animals
compared to the control parameters (main and recovery groups).

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Macroscopic alterations related to the test item were not detected at the necropsy at the termination of the treatment and at the end of the recovery period.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

There were no test item related lesions in the organs or tissues of high dose animals (no general histopathological examination was performed for low and mid dose
animals).

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

A test item effect on the estrous cycle was not detected at any dose level. In accordance with this observation, histopathological examinations did not reveal
changes in the morphology of uterus or ovaries in this study.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects caused by the test item were observed during the study.

Target system / organ toxicity

Key result

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

Under the conditions of the present study, Diethyl carbonate did not cause adverse
effects in male or female Han:WIST rats after 90/91-day consecutive oral (by gavage) administration of 100, 300 or 1000 mg/kg bw/day doses.

There were no toxic changes in the examined parameters (clinical signs, body weight
and body weight gain, food intake, ophthalmology, hematology, blood coagulation and clinical chemistry, serum levels of thyroid hormones, estrous cycle necropsy findings, organ weights or histopathological findings).

Based on the observations made in this toxicity study the No Observed Adverse Effect
Level (NOAEL) was determined as follows.

NOAEL: 1000 mg/kg bw/day for male and female animals

Executive summary:

The objective of this study was to obtain information on the possible health hazards likely to arise from repeated exposure of Diethyl carbonate over a 90/91-day period of time covering post-weaning maturation and growth well into adulthood followed by a 28-day recovery (post treatment) period in order to assess reversibility, persistence or delayed occurrence of potential toxic effects according to OECD 408.The study intended to provide information on the major toxic effects, indicate target organs and the possibility of accumulation, and an estimate of a no-observed-adverse-effect level (NOAEL) of exposure.

Four dose groups of Han:WIST ratsconsisting of15 animals/sex in the control and highest dose groups – including recovery animals – and 10 animals/sex in the low and middle dose groups were administered orally (by gavage) once daily at 0 (vehicle only), 100, 300and 1000 mg/kg body weight/day (mg/kg bw/day) doses in concentrations of 0, 25, 75and 250 mg/mL corresponding to a 4 mL/kg bw dosing volume. A group of vehicle (Sunflower oil) treated animals (n= 15/sex) served as a control.

The suitability of the chosen vehicle (recovery and stability) for the test item at the intended concentrations was analytically verified up front.

Diethyl carbonateconcentrations in the dose forms used for administration of animals varied within the range of 95 % to 100 % in comparison to the nominal values, thereby confirming proper dosing.

 

General clinical cage side observations were made once a day, at approximately the same time after treatment and during the course of the recovery period. Detailed clinical observations were performed weekly during the treatment and recovery period andfunctional observations were made during the last week of treatment and recovery periods. Body weights and food consumption were determined weekly during the entire study.Ophthalmologic examinations were performed on all animals being considered for study before the first treatment and on all animals of the control and high dose groups during the last week of treatment and recovery periods.Clinical pathology (hematology, blood coagulation, clinical chemistry andthyroid hormones) and gross pathology examinations were conducted on all animals one day after the last treatment and at the end of the recovery period. Selected organs were weighed. Full histopathological examinations were performed on the organs and tissues of the control and high dose groups (main and recovery groups). The estrous cycle of each female animal was examined on the day of necropsy.

The results of this study were summarized as follows:

Mortality: There was no mortality during the course of the study.

Clinical observations: No clinical signs related to the test item were found at general daily

or detailed weekly clinical observations at 100, 300 and 1000 mg/kg bw/day. The functional

observations did not reveal any test item influence on the animal behavior or neurological functions.

Body weight and body weight gain: There were no test item related changes in the mean body weight and body weight gain in the male and female animals at 100, 300 and

1000 mg/kg bw/day.

Food consumption: No adverse effects on the mean food consumption development were observed at 100, 300 or 1000 mg/kg bw/day in male or female animals (main and recovery groups).

Ophthalmoscopy: No alterations were detected in the eyes of the animals of the high dose group at the end of treatment or recovery periods.

Hematology and blood coagulation: There were no test item related adverse pathological changes in the investigated  hematological or blood coagulation parameters  in any group

(main and recovery groups).

Clinical chemistry: Pathological test item effects were not detected upon the evaluation of the clinical chemistry parameters in male or female animals at 100, 300 and 1000 mg/kg

bw/day (main and recovery groups).

Determination of serum levels of thyroid hormones: In male and female animals at 100, 300 and 1000 mg/kg bw/day the level of FT3 (free T3) and FT4 (free T4) thyroid hormones

were normal at the end of treatment and recovery period. The levels of TSH were below the limit of detection.

Organ weight: No treatment related alterations were found in the organ weight results (absolute weights, relative to the body weight and brain weight) in male and female animals

compared to the control parameters (main and recovery groups).

Histopathology: There were no test item related lesions in the organs or tissues of high dose animals  (no  general  histopathological  examination was performed  for  low and mid  dose

animals).

Estrous cycle examination: A test item effect on the estrous cycle was not detected at any dose level. In accordance with this observation, histopathological examinations did not reveal

changes in the morphology of uterus or ovaries in this study.

Necropsy: Macroscopic alterations related to the test item were not detected at the necropsy at the termination of the treatment and at the end of the recovery period.