Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 121–75–5
NIOSH REL: 10 mg/m3 TWA [skin]
Current OSHA PEL: 15 mg/m3 TWA [skin]
1989 OSHA PEL: 10 mg/m3 TWA [skin]
1993-1994 ACGIH TLV: 10 mg/m3 TWA [skin]
Description of substance: Deep-brown to yellow liquid with a garlic-like odor.
LEL: . . Unknown
Original (SCP) IDLH: 5,000 mg/m3
Basis for original (SCP) IDLH: No useful data on acute inhalation toxicity are available on which to base the IDLH for malathion. The chosen IDLH, therefore, has been estimated from the statement by Stolman  that the acute oral LD50 values for mice and rats range from 480 to 5,800 mg/kg.
Short-term exposure guidelines: None developed
ACUTE TOXICITY DATA:
Lethal concentration data:
|Species||Reference||LC50||LCLo||Time||Adjusted 0.5-hrLC (CF)||Derived value|
|Cat||Izmerov et al. 1982||—–||10 mg/m3||4 hr||20 mg/m3 (2.0)||20 mg/m3 (2.0)|
|Rat||Sapegin & Mikhailov 1986||84.6 mg/m3||—–||4 hr||169 mg/m3 (2.0)||17 mg/m3|
Lethal dose data:
|Species||Reference||Route||LD50(mg/kg)||LDLo(mg/kg)||Adjusted LD||Derived value|
|Rat||Izmerov et al. 1982||oral||290||—–||2,030 mg/m3||203 mg/m3|
|Mouse||Izmerov et al. 1982||oral||190||—–||1,330 mg/m3||133 mg/m3|
|G. pig||von Dozent et al. 1955||oral||570||—–||3,990 mg/m3||399 mg/m3|
Human data: Workers exposed to initial concentrations up to 85 mg/m3 for 1 hour (that may have declined rapidly) over 42 consecutive days suffered no adverse effects [Golz 1959]. Workers exposed to concentrations that peaked at 56 mg/m3 and averaged 3.3 mg/m3 for 5 hours had normal cholinesterase levels [Culver et al. 1956]. A lethal oral dose of 246 to 471 mg/kg has been reported [Farago 1967; Jusic and Milic 1978]. [Note: An oral dose of 246 to 471 mg/kg is equivalent to a 70-kg worker being exposed to about 11,500 to 22,100 mg/m3 for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]
|Revised IDLH: 250 mg/m3Basis for revised IDLH: The revised IDLH for malathion is 250 mg/m3 based on acute toxicity data in humans [Farago 1967; Golz 1959; Jusic and Milic 1978].|
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2. Farago A . Fatal, suicidal malathion poisonings. Arch Toxikol 23:11-16 (in German).
3. Golz HH . Controlled human exposures to malathion aerosols. AMA Arch Ind Health 19:516-523.
4. Izmerov NF, Sanotsky IV, Sidorov KK . Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 56.
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