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EPN																				Related Pages
										May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)
**CAS number:** 2104–64–5
**NIOSH REL:** 0.5 mg/m3 TWA [skin]
**Current OSHA PEL:** 0.5 mg/m3 TWA [skin]
**1989 OSHA PEL:** Same as current PEL
**1993-1994 ACGIH TLV:** 0.5 mg/m3 TWA [skin]
**Description of Substance:** Yellow solid with an aromatic odor.
**LEL:**. . Noncombustible Solid
**Original (SCP) IDLH:** 50 mg/m3
**Basis for original (SCP) IDLH:** No data on acute inhalation toxicity are available on which to base the IDLH for EPN. The chosen IDLH, therefore, has been estimated from the female rat oral LD50 of 8 mg/kg [Gaines 1969 cited by NIOSH 1976].
**Short-term exposure guidelines:** None developed
**ACUTE TOXICITY DATA**
**Lethal dose data:**

**Species**
    **Reference**
    **Route**
    **LD50** **(mg/kg)**
    **LDLo** **(mg/kg)**
    **Adjusted LD**
    **Derived value**Dog RatRatRatMouse
    AAPCO 1966 Gaines 1969Gaines 1969Hodge et al. 1954Nishizawa et al. 1962
    oral oraloraloraloral
    20 836712.2
    ----- --------------------
    140 mg/m356 mg/m3252 mg/m349 mg/m385 mg/m3
    14 mg/m35.6 mg/m325 mg/m34.9 mg/m38.5 mg/m3
 **Human data:** Ingestion of 3 mg EPN per day for 32 days did not depress plasma or red blood cell (RBC) cholinesterase; 6 mg EPN per day for 88 days did not cause a significant depression of RBC or plasma cholinesterase [Rider et al. 1959]. It has been reported that the threshold of incipient toxicity appears to be 9 mg [Moeller and Rider 1962].
 
 **Revised IDLH:** 5 mg/m3**Basis for revised IDLH:** No inhalation toxicity data are available on which to base an IDLH for EPN. Therefore, the revised IDLH for EPN is 5 mg/m3 based on acute oral toxicity data in humans [Rider et al. 1959] and animals [Gaines 1969; Hodge et al. 1954]. This may be a conservative value due to the lack of relevant acute inhalation toxicity data for workers.
**REFERENCES:**
1. AAPCO [1966]. Pesticide chemicals official compendium. Topeka, KS: Association of the American Pesticide Control Officials, Inc., pp. 478-479.
2. Gaines TB [1969]. Acute toxicity of pesticides. Toxicol Appl Pharmacol *14*:515-534.
3. Hodge HC, Maynard EA, Hurwitz L, DiStefano V, Downs WL, Jones CK, Blanchet HJ Jr [1954]. Studies of the toxicity and of the enzyme kinetics of ethyl p-nitrophenyl thionobenzene phosphonate (EPN). J Pharmacol Exp Ther *112*:29-39.
4. Moeller HC, Rider JA [1962]. Plasma and red blood cell cholinesterase activity as indications of the threshold of incipient toxicity of ethyl-p-nitrophenyl thionobenzenephosphonate (EPN) and malathion in human beings. Toxicol Appl Pharmacol *4*:123-130.
5. NIOSH [1976]. TB19250. Phosphonothioic acid, phenyl-, O-ethyl O-(P-nitrophenyl)ester. In: Registry of toxic effects of chemical substances, 1976 ed. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-191, p. 877.
6. Nishizawa Y, Kuramoto S, Kadota T, Miyamoto J, Fujimoto K, Sakamoto H [1962]. Studies on organophosphorus insecticides. Part X. Chemical and biological properties of O,O-dimethyl-O-(4-cyanophenyl) phosphorothioate and O-ethyl-O-(4-cyanophenyl) phenyl phosphonothioate. Agri Biol Chem *26*(4):257-264.
7. Rider JA, Moeller HC, Swader J, Devereaux RC [1959]. A study of the anticholinesterase properties of EPN and malathion in human volunteers. Clin Res *7*:81-82.

			
							
								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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