Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 1910–42–5
NIOSH REL: 0.1 mg/m3 (respirable dust) TWA [skin]
Current OSHA PEL: 0.5 mg/m3 (respirable dust) TWA [skin]
1989 OSHA PEL: 0.1 mg/m3 (respirable dust) TWA [skin]
1993-1994 ACGIH TLV: 0.1 mg/m3 (respirable dust) TWA,
0.5 mg/m3 (total dust) TWA
Description of substance: Yellow solid with a faint, ammonia-like odor.
LEL: . Noncombustible Solid
Original (SCP) IDLH: 1.5 mg/m3
Basis for original (SCP) IDLH: The chosen IDLH is based on the statements by Gage  that “after single exposures the LC50 appears to be a function of the duration and of the concentration; in the rat the lethal concentration-time product is about 6 micrograms/liter-hour. Guinea pigs and male mice are about as sensitive as rats. Female mice are less sensitive. The dog can tolerate a concentration-time product of 25 micrograms/liter-hour without ill effects.”
Short-term exposure guidelines: None developed
ACUTE TOXICITY DATA:
Lethal concentration data:
|Species||Reference||LC50||LCLo||Time||Adjusted 0.5-hrLC (CF)||Derived value|
|Respirable dust G. pig||Gage 1968||3 mg/m3||—–||30 min||3.0 mg/m3 (1.0)||0.30 mg/m3|
|Respirable dust Mouse||Gage 1968||3 mg/m3||—–||30 min||3.0 mg/m3 (1.0)||0.30 mg/m3|
|Respirable dust Rat||Gage 1968||—–||1 mg/m3||6 hr||2.3 mg/m3 (2.3)||0.23 mg/m3|
|Nonrespirable dust Rat||Palazzolo 1965||—–||6,400 mg/m3||4 hr||12,800 mg/m3 (2.0)||1,280 mg/m3|
Lethal dose data:
|Species||Reference||Route||LD50(mg/kg)||LDLo(mg/kg)||Adjusted LD||Derived value|
|Bailey & White 1965Barabas et al. 1981
Murray &Gibson 1972
|399 mg/m3840 mg/m3
|40 mg/m384 mg/m3
Human data: It has been stated that the high acute inhalation toxicity of paraquat is dependent wholly on the size of the particulate, with respirable sizes (i.e., <5 micrometer mass median diameter) found to be 5 to 6 times more toxic than nonrespirable dusts [McElligo 1965]. It has been reported that under paraquat spraying conditions particle sizes appear to be nonrespirable [Swan 1969].
|Revised IDLH: 1 mg/m3Basis for revised IDLH: The revised IDLH for paraquat is 1 mg/m3 based on the acute inhalation toxicity data for respirable particulate in animals [Gage 1968]. This is a conservative value if the occupational exposure is totally to nonrespirable size particles of paraquat since respirable aerosols are much more toxic [McElligo 1965; Swan 1969].|
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2. Barabas K, Vigh L, Horvath I, Szabo L, Matkovics B . Effects of paraquat in vivo on fatty acids of mouse and guinea pig tissues. Gen Pharmacol 12:225-227.
3. Gage JC . Toxicity of paraquat and diquat aerosols generated by a size-selective cyclone: effect of particle size distribution. Br J Ind Med 25:304-314.
4. Iyakuhin Kenkyu (Study of Medical Supplies) ; 10:520-522 (in Japanese).
5. McElligo TF . Industrial hygiene research lab report IHR/172. Alderly Park, Macclesfield, Cheshire, England: Imperial Chemicals Industries, Ltd. [From ACGIH . Paraquat. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 1159-1161.]
6. Murray RE, Gibson JE . A comparative study of paraquat intoxication in rats, guinea pigs and monkeys. Exp Molec Pathol 17:317-325.
7. Palazzolo RF . Report to Imperial Chemical Industries, Ltd. Alderly Park, Macclesfield, Cheshire, England. [From ACGIH . Paraquat. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 1159-1161.]
8. Swan AAB . Exposure of spray operators to paraquat. Br J Ind Med 26:322-329.