Diethoxymethane

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP lab following strict internal SOP similar to OECD Annex V B 8 (Sub-acute inhalation toxicity) with full QA oversight

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: EPA TG-412

Deviations:

yes

Remarks:

two weeks rather than 28 days

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: OECD Annex V B 8: sub-acute inhalation toxicity

Deviations:

yes

Remarks:

two weeks rather than 28 days

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Diethoxymethane

EC Number:

207-330-6

EC Name:

Diethoxymethane

Cas Number:

462-95-3

Molecular formula:

C5H12O2

IUPAC Name:

diethoxymethane

Details on test material:

- Name of test material (as cited in study report): Diethoxymethane
- Physical state: liquid
- Analytical purity: 99.9%
- Impurities (identity and concentrations): pyrogallol 10 ppm
- Lot/batch No.: X-19085-9
- Stability under test conditions: stable
- Storage condition of test material: room temperature

Test animals

Species:

rat

Strain:

other: CRL: CD (SD) BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Age at study initiation: 8 weeks
- Weight at study initiation: 222-257g (males) and 205-232g (females)
- Fasting period before study: no
- Housing: group housed in stainless steel during the isolation period. Singly housed in multicompartmented stainless steel mesh cages designed for inhalation studies afterwards
- Diet (e.g. ad libitum): ad libitum during nonexposure periods
- Water (e.g. ad libitum): ad libitum during nonexposure periods
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.5-23°C during acclimatation and 20-22°C during study
- Humidity (%): 50-52% during acclimatation and 56-61% during study
- Photoperiod (hrs dark / hrs light): 12/12

The following protocol deviation was observed during the study but was not expected to interfere with its outcome. The animal housing quarters temperature fluctuated to one degree Fahrenheit less than the lower limits specified in protocol.

IN-LIFE DATES: From: June 9 1986 To: June 25 1986

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: Not applicable. Exposure to vapor only.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 420l stainless steel and glass inhalation chambers
- Method of holding animals in test chamber: cages
- Source and rate of air: metered, dried, oil free compressed air. 12 air changes per hour
- System of generating vapour: atmospheres produced by passing air over the surface of the test material
- Temperature, humidity, pressure in air chamber: 20-22°C, 56-61%, 125Pa
- Air change rate: 12 /hour
-Method of particle size determination: Twice during exposure, concentration of background nongaseous material was measured in the high dose chamber relative to that of air control chamber in order to insure that exposures were to vapor and not aerosol

TEST ATMOSPHERE
- Brief description of analytical method used: Infrared analyzer
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Chamber vapor concentrations were determined at least once per hour by a Miran (c) IA infrared analyzer equipped for automated sampling and analysis. Distribution of test material was determined initially by measurement from numerous positions throughout the test chamber and was compared to a fixed reference position. A coefficient of variation of 3% was observed.
Analytical concentrations were within 15% of the nominal concentrations. There was no aerosol of the test substance present.

Duration of treatment / exposure:

6 h per day except weekends

Frequency of treatment:

12 exposures over 16 days.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0 ppm
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
750 ppm
Basis:
nominal conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
1500 ppm
Basis:
nominal conc.

Doses / concentrations 4

Remarks:

Doses / Concentrations:
3000 ppm
Basis:
nominal conc.

No. of animals per sex per dose:

5 of each sex to each dose

Control animals:

yes, concurrent vehicle

Details on study design:

Animal assignment at random
No satellite groups

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Not seperatly monitored

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: before and after exposition
Observation before and after exposure included examination of the hair, skin, eyes, motor activity, feces and urine. Visual observation of behavior was conducted during exposure.

BODY WEIGHT: Yes
- Time schedule for examinations: on days: 0, 3, 7, 10, 14 and at necropsy

FOOD CONSUMPTION: Not monitored
FOOD EFFICIENCY: Not monitored
WATER CONSUMPTION: Not monitored
OPHTHALMOSCOPIC EXAMINATION: Not monitored

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at necropsy
- Anaesthetic used for blood collection: Yes CO2
- Animals fasted: Yes
- How many animals: all
- Parameters checked included: hemoglobin concentration, hematocrit, red blood cell count, white blood cell count, differential white blood cell count, platelet count, red blood cell indices and examination of the blood smear for cellular morphology.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at necropsy
- Animals fasted: Yes
- How many animals: all
- Parameters checked included: aspartate aminotransferase, alanine aminotransferase, sorbitol dehydrogenase, alkaline phosphatase, creatinine, urea nitrogen and glucose

URINALYSIS: Not monitored

NEUROBEHAVIOURAL EXAMINATION: Not monitored

Sacrifice and pathology:

GROSS PATHOLOGY and HISTOPATHOLOGY were performed at necropsy. For list of examined parameters, please see results tables in documents "Details on results" which is attached under "Attached background material""

Other examinations:

No other examinations

Statistics:

Mean values were calculated for body weight, organ weights, hematology and clinical chemistries. All mean value data were evaluated using one way analysis of variance (ANOVA), Bartlett's test and Duncan's multiple range test using a p value of =< 0.05 to indicate statistical significance

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

lethargy, gel like casts

Mortality:

mortality observed, treatment-related

Description (incidence):

lethargy, gel like casts

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

slightly lower mean corpuscular hemoglobin, in females exposed to 1500 and 3000ppm, non dose dependent

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

relative liver (for males and to a lesser extent females) and adrenal gland (females) weights slightly increased

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

Please see "Attached background material" for full results summary tables

CLINICAL SIGNS AND MORTALITY
There were no death during the study. Lethargy was exhibited by all animals during exposures although the daily frequency differed. The frequency was concentration dependent. Rats exposed to 750 ppm exhibited minimal lethargy on three days, 1500 ppm produced minimal to minor lethargy on 8 days, and 3000 ppm produced minimal to moderate lethargy on all 12 exposure days. Two females exhibited sialorrhea following exposure on one or two days only.
A number of “gel-like” casts were observed beneath the suspended cages of each exposure group (not for controls). They appeared as translucent rods about 5 mm long and 1mm diameter. These have been seen in males in inhalation studies with other compounds and may represent excretion of seminal fluid. These emissions are probably ingested during routine grooming. Exposure to some chemical may reduce this behavior and thus increase the likelihood of observing the plugs.

BODY WEIGHT AND WEIGHT GAIN
Not effects were observed except body weight gain of males exposed to 3000 ppm and 750ppm was slightly lower than controls. These differences were not statistically significant.

HAEMATOLOGY
No effects were observed except a very slight lower mean corpuscular hemoglobin, which was statistically significant but not concentration-dependent, in females exposed to 1500 and 3000 ppm.

CLINICAL CHEMISTRY
No effects were observed except a spurious observation of an elevated sorbitol dehydrogenase level in one male exposed to 1500 ppm.

ORGAN WEIGHTS
Males exposed to 1500 ppm and 3000 ppm exhibited a concentration dependent increase in absolute and relative liver weights. Relative liver weights were also increased in males exposed to 750 ppm. The differences were small with only the relative liver weight showing statistical difference for 1500 and 3000 pm groups.
Males exposed to 750 ppm also showed increased relative kidney weight (statistically significant). This observation was considered as spurious. Absolute weights were not different from control. No other effects were observed on males.
The absolute and relative liver weights of females exposed to 3000 ppm were slightly but statistically higher in comparison to control values. Absolute and relative liver weight for females exposed to 750 ppm and 1500 ppm were comparable to controls.
Moderate, statistically significant increases of in absolute and relative weight of adrenal gland were observed in females exposed to 3000 ppm. A slight decrease in the absolute and relative weight of adrenal glands was observed in the 750 ppm group. Only the relative weight was statistically significant in the latter case. Absolute and relative weights of adrenal glands from female rats exposed to 1500 ppm were comparable to control values. The slights weight loss in adrenal glands associated with exposure to 750 ppm is probably spurious. Adrenal weight increases associated with exposure to 3000 ppm may be compound-related but were small. No other effects were observed on females.

GROSS PATHOLOGY & HISTOPATHOLOGY
No compound related gross pathology or histopathology was observed in animals in any group

Effect levels

1

Dose descriptor:

NOEL

Effect level:

750 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects clinical signs; mortality; body weight; haematology; clinical chemistry; gross pathology; organ weights; histopathology

2

Dose descriptor:

LOEL

Effect level:

1 500 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects clinical signs; mortality; body weight; haematology; clinical chemistry; gross pathology; organ weights; histopathology

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Diethoxymethane (DEM) exhibited a low order of toxicity in rats exposed for two weeks. Except for transient lethargy, plugs (males) and a small increase in relative liver weight (males) a concentration of 750 ppm is probably close to the No observed effect level for toxicity.

Executive summary:

Groups of five male and five female rats were exposed to target vapor concentrations of 0, 750, 1500 or 3000 ppm diethoxymethane (DEM) for 6 hours per exposure, for 12 exposures. Exposure produced transient central nervous system depression in all groups during exposure which resolved shortly after exposure ceased. Gel-like casts or spontaneous seminal plug emissions, which may reflect changes in grooming habits during exposure, were observed beneath the cages in all treatment groups. No deaths occurred during the study. Exposure to DEM produced no toxicologically significant changes in body weight gain, hematology or clinical chemistry. Slight but statistically significant increases in liver weights in males and females and a small increase also statistically significant, in adrenal gland weights in females exposed to 3000 ppm were probably compound-related. There were no compound-related gross or histopathological changes detected. The no-observed-effect level for toxicity was not determined. However, the effects observed following exposure to 1500 and 3000 ppm DEM were all slight. The effects observed at 750 ppm (transient lethargy, casts (males), increased relative liver weight (males)) were of even lesser severity and frequency. A concentration of 750 ppm is probably close to the no-observed-effect level for toxicity.