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Naphtha (coal tar)

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 8030–30–6

NIOSH REL: 100 ppm (400 mg/m3) TWA

Current OSHA PEL: 100 ppm (400 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 400 ppm (1,590 mg/m3) TWA

Description of substance: Reddish-brown, mobile liquid with an aromatic odor.

LEL :. . . 1.0-1.3% (10% LEL, 1,000-1,300 ppm)

Original (SCP) IDLH: 10,000 ppm [LEL]

Basis for original (SCP) IDLH: According to AIHA [1970], 7,500 ppm benzene is judged dangerous to human life for exposures of 30 minutes or more [Henderson and Haggard 1943]. Because benzene is the most hazardous constituent of coal tar naphtha which is present in any appreciable amount, an IDLH of 7,500 ppm could be assumed. However, because the amount of benzene contained in naphtha is usually small, the lower explosive limit (LEL) of 10,000 ppm been used as the IDLH for this draft technical standard. [Note: The draft technical standard noted that the range of the LELs for each of the constituents of coal tar naphtha were between 10,000 and 13,000 ppm.]

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50




Time Adjusted 0.5-hr


Derived value
Rat Carpenter et al. 1975 15,000 ----- 4 hr 30,000 ppm (2.0) 3,000 ppm
Mouse Stubblefield et al. 1989 2,319 ----- 6 hr 5,335 ppm (2.3) 534 ppm
Human Tab Biol Per 1933 ----- 30,000 5 min 16,500 ppm (0.55) 1,650 ppm
Rat Taylor 1939 1,600 ----- 6 hr 3,680 ppm (2.3) 368 ppm

Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value
Rat Stubblefield et al. 1989 oral >5,000 ----- >7,659 ppm >766 ppm

Other human data: Acute exposure to 430 ppm has been reported to cause only slight eye and throat irritation [Carpenter et al. 1975].

Revised IDLH: 1,000 ppm [LEL]

Basis for revised IDLH: Based on health considerations and acute inhalation toxicity data in humans [Carpenter et al. 1975; Tab Biol Per 1933], a value of about 1,700 ppm would have been appropriate for coal tar naphtha. However, the revised IDLH for coal tar naphtha is 1,000 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limits of the various constituents of coal tar naphtha which range from 1.0 to 1.3%).


1. AIHA [1970]. Benzene. In: Hygienic guide series. Am Ind Hyg Assoc J 31:383-388.

2. Carpenter CP, Kinkead ER, Geary DL Jr, Sullivan LJ, King JM [1975]. Petroleum hydrocarbon toxicity studies. IV. Animal and human response to vapors of rubber solvent. Toxicol Appl Pharmacol 33:526-542.

3. Henderson Y, Haggard HW [1943]. Noxious gases. 2nd ed. New York, NY: Reinhold Publishing Corporation, p. 213.

4. Stubblefield WA, McKee RH, Kapp RW Jr, Hinz JP [1989]. An evaluation of the acute toxic properties of liquids derived from oil sands. J Appl Toxicol 9(1):59-65.

5. Tab Biol Per [1933]; 3:231 (in German).

6. Taylor H [1939]. Toxicity of coal tar naphtha distillates. Chem Ind 17:1078-1080.