Methylhydrazine

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP, no guideline mentionned, but similar to the applicable guideline and adequate design and coherence. Unknown purity is the only aspect with possible impact on results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1969

Report date:

1969

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

not referenced but similar

GLP compliance:

no

Remarks:

prior to GLP

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methylhydrazine

EC Number:

200-471-4

EC Name:

Methylhydrazine

Cas Number:

60-34-4

Molecular formula:

CH6N2

IUPAC Name:

methylhydrazine

Details on test material:

- name: monomethylhydrazine, MMH
- MMH manufactured under military specification MIL-P-27404
- long term storage was avoided, and any samples showing decomposition or discoloration were discarded.
- purity not mentionned

Test animals

Species:

other: see below

Strain:

other: see below

Details on test animals or test system and environmental conditions:

- Groups of 10 male Sprague-Dawley rats (125-175 g)
- Groups of 20 male ICR (Swiss) mice (17-23 g) - x2 parallel experiments
- Groups of 1 to 5 male and/or female beagle dogs, 8 to 30 months of age (7 to 13 kg)
- Groups of 1 to 5 young female squirrel monkeys (Saimiri sciurea) (560 to 680 g)
- Groups of 1 or 2 male and/or female rhesus monkeys (Macaca mulatta).
care was taken to include as much as possible the same range of body weights in each of the exposure groups.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: nitrogen-air mixture

Details on inhalation exposure:

Rodents were exposed for 30-, 60-, 120-, and 240-minute periods,
dogs and squirrel monkeys for 15, 30, and 60 minutes,
and rhesus monkeys for 60 minutes only.

exposure: filtered air in Rochester Chambers; MMH was introduced under nitrogen.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

by electron capture instrument measuring a MMH / trifluoroacetic acid reaction

Duration of exposure:

>= 0.25 - <= 4 h

Remarks on duration:

see above

Concentrations:

Initial analytical and toxicity experiments evidenced oxidative degradation of MMH. Therefore corrective changes were made to equipment
and methods to provide the air flow capacity, temperature, and relative humidity control necessary for conducting animal exposures to unreacted MMH.

No. of animals per sex per dose:

see above

Control animals:

yes

Details on study design:

All rodents were weighed on the day of exposure, at least 3-, 7-, and 14-day postexposure, and observed for toxic signs during exposure and for 14 days.
All dogs/monkeys were weighed on the day of the exposure; symptoms of toxic stress observed during exposure and postexposure until the animals died or were killed for pathologic examination were recorded.

Hematology and blood chemistry determinations were made before and after exposure at several intervals, on blood samples collected from the femoral vein of the rhesus monkeys and from the jugular or cephalic vein of the beagles.

Some rodents that died during or were killed following exposure were submitted for histopathologic studies of the lung, liver, kidney, heart,
and spleen after routine gross examination. All dogs/monkeys that died during or following exposure were submitted for postmortem gross and histopathologic examination.

Statistics:

The respective LC50 values and their 95% confidence limits were calculated by
- rodents: the probit method utilizing the BMD03S Computer Program
- dogs/monkeys: Thompson method of moving averages

Results and discussion

Preliminary study:

The initial animal exposure attempts showed that MMH was a highly toxic substance that required the use of relatively low concentrations.

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

LC50

Effect level:

65 ppm

Based on:

test mat.

95% CL:

63 - 66

Exp. duration:

4 h

Remarks on result:

other: mouse

Effect levels 2

Sex:

male

Dose descriptor:

LC50

Effect level:

78 ppm

Based on:

test mat.

95% CL:

71 - 86

Exp. duration:

4 h

Remarks on result:

other: rat

Effect levels 3

Sex:

female

Dose descriptor:

LC50

Effect level:

82 ppm

Based on:

test mat.

95% CL:

67 - 101

Exp. duration:

1 h

Remarks on result:

other: squirrel monkey

Effect levels 4

Sex:

male/female

Dose descriptor:

LC50

Effect level:

96 ppm

Based on:

test mat.

Exp. duration:

1 h

Remarks on result:

other: dog

Effect levels 5

Sex:

male/female

Dose descriptor:

LC50

Effect level:

162 ppm

Based on:

test mat.

95% CL:

118 - 222

Exp. duration:

1 h

Remarks on result:

other: rhesus monkey

Effect levels 6

Sex:

male/female

Dose descriptor:

other: LOAEC for hemolysis

Effect level:

<= 92 ppm

Based on:

test mat.

Exp. duration:

1 h

Remarks on result:

other: dog

Mortality:

extremely steep dose-lethality curves in all species. no measurable difference due to sex.

rodents, dogs and squirrel monkeys: LC50 x Exposure Time was a constant, with:
- dog: LC50 x T = 5860 ppm.min
- squirrel monkey: LC50 x T = 4840 ppm.min
- these data enable extrapolation of LC50 for the required 4h duration for classification.

Clinical signs:

other: dose and concentration-dependent lists: Rodents: - irritation of nose and eyes - diarrhea, abnormally frequent urination and more rapid labored breathing - Increased alertness; piloerection; hyperactivity, interrupted by periods of inactivity with rigid

Body weight:

loss or reduced gain

Gross pathology:

all species:
pulmonary congestion with some hemorrhage, hepatic congestion of varying degree, and swelling of the renal tubular epithelium which was frequently glassine and eosinophilic in appearance.

In large animals whose brain tissues were examined, subarachnoid hemorrhage was frequently observed (probably related to the severe convulsions); in dogs remarkably bloodless spleens in which the sinusoids were virtually empty. In some cases, the splenic smooth muscle bundles appeared thickened and contracted.
The amount of visceral congestion / hemorrhage observed was not sufficient to produce death: death was due to CNS damage only.

At 2 months post-exposure, renal damage from mild swelling of the tubular epithelium to vacuolization and coagulative necrosis of those epithelial cells, was noted.

Other findings:

blood in urine/feces, frequent, in dogs (all doses)

Hematocrit, hemoglobin, red blood cell and reticulocyte values obtained from blood samples taken before, immediately after, and twice weekly postexposure from surviving dogs and rhesus monkeys clearly indicated red blood cell hemolysis. Anemia occured in all exposed dogs and rhesus monkeys (all doses). Recovery took around one month.

Applicant's summary and conclusion

Interpretation of results:

very toxic

Remarks:

Migrated information also Acute Tox 1 Criteria used for interpretation of results: EU

Executive summary:

Key data after acute inhalation of MMH:

• Lethality: LC50-4h values:

- squirrel monkey: 20 ppm*

- dog: 24 ppm*

- rhesus monkey: 40 ppm**

- mouse: 65 ppm

- rat: 78 ppm

The lowest of above values corresponds to 38 µg/L at 25°C, atmospheric pressure.

• Intense hemolytic anemia with halving of all RBC parameters, taking up to 2 months to recover, occured at or extremely close to the LC50, notably at 0.047 mg/L** in dogs (23 ppm**).

*: extrapolated for higher duration based on demonstration LC50 x Time = constant

**: same approach assumed as for *, extended to another species and/or sublethal effects