Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Additional information

Several studies concerning the acute toxicity of methylhydrazin (MH) are available in open literature. For an overview please see:

- ACGIH 2001: Methylhydrazine TLV-TWA

- MAK (german "maximum concentration value at the workplace") derivation of 1988.

Acute toxicity effects: convulsion, neurological effects, hypoglycemia, vomiting, anemia, bilirubinemia, increased methemoglobinemia.

Acute oral LD 50 values:

Mouse:       33 mg/kg bw

rat:              32 / 71 mg/kg bw

hamster:       22 mg/kg bw

Dermal LD 50 values:

Hamster:              183 and 239 mg/kg bw

Guinea pig:            47 mg / kg bw

rabbit:                   93 mg / kg bw

The substance is readily absorbed by the skin: Undiluted MH applied to the skin of dogs was detected in blood within 30 seconds following application.

Inhalation LC50 values:

rats 74 - 78 ppm (4 -hour exposure) = 74 ppm vapour = (74 ppm x 47 [molecular weight] / 24,1 [factor at RT]) = 0,144 mg/L

mice 56 - 65 ppm (4 -hour exposure)

monkeys 162 ppm (1 -hour exposure)

dogs 96 ppm (1 -hour exposure)


Methylhydrazine can cause adverse effects on the blood (hemolysis, methemoglobin) and on the CNS (tonic-clonic convulsions). Effects on the lung (irritation) are covered by the classification as being corrosive.

Justification for classification or non-classification

According to the effects described, the substance is classified:


DSD: R25 - Toxic if swallowed / GHS: Acute Toxicity (oral) Cat. 2


DSD: R24 - Toxic in contact with skin / GHS: Acute Toxicity (dermal) Cat. 2


DSD: R28 - Very toxic by inhalation / GHS: Acute Toxicity (inhalation) Cat. 1

STOT SE Cat. 1 (Target Organs: blood and CNS).