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Paraquat																				Related Pages
										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-hr** **LC (CF)**
    **Derived value**Respirable dust G. pig
    Gage 1968
    3 mg/m3
    -----
    30 min
    3.0 mg/m3 (1.0)
    0.30 mg/m3Respirable dust Mouse
    Gage 1968
    3 mg/m3
    -----
    30 min
    3.0 mg/m3 (1.0)
    0.30 mg/m3Respirable dust Rat
    Gage 1968
    -----
    1 mg/m3
    6 hr
    2.3 mg/m3 (2.3)
    0.23 mg/m3Nonrespirable 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**Rat MouseDogG. pig
    Bailey & White 1965 Barabas et al. 1981Iyakuhin 1979Murray &Gibson 1972
    oral oraloraloral
    57 1202522
    ----- ---------------
    399 mg/m3840 mg/m3175 mg/m3154 mg/m3
    40 mg/m384 mg/m318 mg/m315 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/m3**Basis 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].**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.

			
							
								Page last reviewed:  December 4, 2014						Content
							source: 	National Institute for Occupational Safety and Health NIOSH Publications & Products
Immediately Dangerous To Life or Health (IDLH) Values
Table of IDLH Values
Criteria for Determining IDLH Values
Historical Documentation
Original (SCP) Values
Abbreviations for IDLH Documentation
Abbreviations for Journal Titles Follow NIOSH Facebook
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