Trimethyl orthoacetate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

limited documentation

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Toxicological Research of Methanol as a fuel for Power Station. Summary Report on Tests with Monkeys, Rats and Mice.

Author:

New Energy Development Organization

Year:

1987

Bibliographic source:

New Energy Development Organization, Tokyo

Reference 2

Reference Type:

publication

Title:

Long-term effects of methanol vapor at low concentration.

Author:

Takeda, K. and Katoh, N.

Year:

1988

Bibliographic source:

Proc. of the 8th Int. Symp. Alcohol Fuels, 1051-1056, Tokyo, Japan

Reference 3

Reference Type:

publication

Title:

Methanol, Environmental Health Criteria 196

Author:

IPCS/WHO

Year:

1997

Bibliographic source:

International Programme on Chemical Safety, World Health Organisation Geneva, 1997

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

- limited documentation

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methanol

EC Number:

200-659-6

EC Name:

Methanol

Cas Number:

67-56-1

Molecular formula:

CH4O

IUPAC Name:

methanol

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan Inc.
- Age at study initiation: 6 weeks
- Housing: The animals were housed individually in wire-mash cages attached to the inhalation chamber.
- Diet (e.g. ad libitum): solid chow for mice (CRF-1, Charles River Japan Inc.)
- Water (e.g. ad libitum): filtered and sterilised tap water
- Acclimation period: 6 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 °C
- Humidity (%): 55 ± 15 %
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: not applicable

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Hazleton 1000 Inhalation Exposure Chamber

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analytical control of chamber concentration: analytical values close to nominal ones.

Duration of treatment / exposure:

12 months (males: 7202-7225 h; females: 7352-7373 h)

Frequency of treatment:

continuously, mean daily exposure time: 19.8 hours

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0.013 mg/L air (nominal)

Remarks:

corresponding to 10 ppm

Doses / concentrations 2

Dose / conc.:

0.13 mg/L air (nominal)

Remarks:

corresponding to 100 ppm

Doses / concentrations 3

Dose / conc.:

1.3 mg/L air (nominal)

Remarks:

corresponding to 1000 ppm

No. of animals per sex per dose:

30

Control animals:

yes

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes


DETAILED CLINICAL OBSERVATIONS: Yes


BODY WEIGHT: Yes
- Measurements were carried out on all animals once a week.


FOOD CONSUMPTION:
- The measurements were done weekly during the first 13 weeks of exposure, and monthly thereafter.


HAEMATOLOGY: Yes


CLINICAL CHEMISTRY: Yes


URINALYSIS: Yes

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
For interim examination, 10 animals per sex and dose were sacrificed after 6 months.

Statistics:

All the data obtained were analysed by t-test, Fischer´s exact test or Armitage´s chi-square test as appropriate for any significant difference.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

During the whole study, there were no changes in the general appearance that could suggest any relation to methanol treatment.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

One female animal of the 0.13 mg/L group died on day 174, another female animal (also of the 0.13 mg/L group) had to be sacrificed in moribund state on day 178.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body-weights of both sexes of the treated groups tended to be higher than the controls in the second half of the study (NEDO, Fig. 3, p. 168).

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

There was decreased food consumption in high-dose females during the first 2 months and from month 7 throughout the study.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

All clinical and blood tests failed to reveal any methanol-related alteration in parameters from normal.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

All clinical and blood tests failed to reveal any methanol-related alteration in parameters from normal.

Urinalysis findings:

no effects observed

Description (incidence and severity):

Urinary protein was in the normal range of physiological variations. None of pH, glucose, ketones, bilirubin, occult blood or urobilinogen showed any changes suggesting effects from the treatment.

Behaviour (functional findings):

not examined

Immunological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

In the group of high-dose females, an increase in organ weight with significant differences was noted for the liver after 6 months and for the kidney and spleen after 12 months, however, the latter without statistical significance and a clear dose-response.
The organ/body weight ratio did not show any significant difference.

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Histopathological examinations revealed various non-tumoral changes. Except for vacuolar degeneration of the ureter epithelium at the kidney, all findings were observed due to aging or of accidental nature commonly seen in mice of this age and strain (6 or 12 month old, B6C3F1).

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Necropsy of animals sacrificed after 6 or 12 months of treatment revealed a sporadical incidence of accidental changes for both males and females. But there were no changes which occurred in a high incidence or specifically in the treated groups.
The two females of the mid-dose group (0.13 mg/L) which died or were sacrificed in extremis had thoracic or abdominal dropsy, atrophy of the thymus and spleen, severe roughness and grey-coloration of the kidney surface.
Liver: After 12 months, the incidence of more severe fatty degeneration of hepatocytes was pronounced in high-dose males: This was graded as moderate in 8/20, mild in 8/20 and negative in 4/20 surviving males vs. 1/20 (moderate), 9/20 (mild) and 10/20 negative in the male control group. On the other hand, this effect was common and found to similar extent in untreated/external male mice. The female mice showed no difference among the groups compared to control.

Effect levels

1

Key result

Dose descriptor:

NOAEC

Effect level:

1.3 mg/L air (nominal)

Sex:

male/female

Basis for effect level:

other: histopathological examinations; body weight; food consumption; organ weights

2

Key result

Dose descriptor:

NOEC

Effect level:

0.13 mg/L air (nominal)

Sex:

male/female

Basis for effect level:

other: histopathological examinations; body weight; food consumption; organ weights

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

According to the authors, only in the 1.3 mg/L dose-group changes could be considered treatment-related. But based on the minor degree and severity, these changes have no pathological meaning and are considered as toxicologically irrelevant.

Levels of 0.13 mg/L or less did not produce any effect (=NOEC). 1.3 mg/L can be established as NOAEC, while it is the LOEC for non-pathological, apparently treatment-related effects.