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

CAS number: 91–20–3

NIOSH REL: 10 ppm (50 mg/m3) TWA, 15 ppm (75 mg/m3) STEL

Current OSHA PEL: 10 ppm (50 mg/m3) TWA

1989 OSHA PEL: 10 ppm (50 mg/m3) TWA, 15 ppm (75 mg/m3) STEL

1993-1994 ACGIH TLV: 10 ppm (52 mg/m3) TWA, 15 ppm (79 mg/m3) STEL

Description of substance: Colorless to brown solid with an odor of mothballs.

LEL: . . . 0.9% (10% LEL, 900 ppm)

Original (SCP) IDLH: 500 ppm

Basis for original (SCP) IDLH: No useful data on acute inhalation toxicity are available on which to base the IDLH for naphthalene. The chosen IDLH, therefore, has been estimated from the probable oral lethal dose of 5 to 15 grams for an adult [Gerarde 1960 cited by AIHA 1967].

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value

G. pig


Gosselin et al. 1984Izmerov et al. 1982

Matorova 1982

Shopp et al. 1984










2,355 ppm641 ppm

1,570 ppm

697 ppm

236 ppm64 ppm

157 ppm

70 ppm

Human data: The probable oral lethal dose has been reported to be between 5 and 15 grams [Gerarde 1960]. [Note: An oral dose between 5 and 15 grams is equivalent to a worker being exposed to about 600 to 1,800 ppm for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]


1. AIHA [1967]. Naphthalene. In: Hygienic guide series. Am Ind Hyg Assoc J 28:493-496.

2. Gerarde HW [1960]. Toxicology and biochemistry of aromatic hydrocarbons. Princeton, NJ: Elsevier Publishing Company, p. 228.

3. Gosselin RE, Smith RP, Hodge HC [1984]. Clinical toxicology of commercial products. 5th ed. Section III. Therapeutics Index. Baltimore, MD: Williams & Wilkins Company, pp. 307-310.

4. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 89.

5. Matorova NI [1982]. Data on establishing the maximum permissible concentration of naphthalene and chloronaphthalene in reservoir water. Gig Sanit 11:78-79 (in Russian).

6. Shopp GM, White KL Jr, Holsapple MP, Barnes DW, Duke SS, Anderson AC, Condie LW, Hayes JR, Borzelleca JF [1984]. Naphthalene toxicity in CD-1 mice: general toxicology and immunotoxicology. Fundam Appl Toxicol 4:406-419.