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Paraquat

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May 1994
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 [1968] 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
RatMouse

Dog

G. pig

 Bailey & White 1965Barabas et al. 1981

Iyakuhin 1979

Murray &Gibson 1972

 oraloral

oral

oral

 57120

25

22

 ———-

—–

—–

 399 mg/m3840 mg/m3

175 mg/m3

154 mg/m3

 40 mg/m384 mg/m3

18 mg/m3

15 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].

REFERENCES:

1. Bailey GW, White JL [1965]. Herbicides: a compilation of their physical, chemical, and biological properties. Residue Reviews 10:97-102.

2. Barabas K, Vigh L, Horvath I, Szabo L, Matkovics B [1981]. Effects of paraquat in vivo on fatty acids of mouse and guinea pig tissues. Gen Pharmacol 12:225-227.

3. Gage JC [1968]. 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) [1979]; 10:520-522 (in Japanese).

5. McElligo TF [1965]. Industrial hygiene research lab report IHR/172. Alderly Park, Macclesfield, Cheshire, England: Imperial Chemicals Industries, Ltd. [From ACGIH [1991]. 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 [1972]. A comparative study of paraquat intoxication in rats, guinea pigs and monkeys. Exp Molec Pathol 17:317-325.

7. Palazzolo RF [1965]. Report to Imperial Chemical Industries, Ltd. Alderly Park, Macclesfield, Cheshire, England. [From ACGIH [1991]. 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 [1969]. Exposure of spray operators to paraquat. Br J Ind Med 26:322-329.