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

CAS number: 7553–56–2

NIOSH REL: 0.1 ppm (1 mg/m3) CEILING

Current OSHA PEL: 0.1 ppm (1 mg/m3) CEILING

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.1 ppm (1 mg/m3) CEILING

Description of substance: Violet solid with a sharp, characteristic odor.

LEL:. . Noncombustible Solid

Original (SCP) IDLH: 10 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on an analogy with bromine which has an IDLH of 10 ppm.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hr LC (CF) Derived value
Rat Izmerov et al. 1982 ----- 76 1 hr 95 ppm (1.25) 9.5 ppm

Lethal dose data:

Species Reference Route LD50




Adjusted LD Derived value




Angelis 1979

Angelis 1979

Angelis 1979

Flury and Zernik 1935













9,289 ppm

14,597 ppm

6,635 ppm

531 ppm

929 ppm

1,460 ppm

664 ppm

53 ppm

Human data: It has been reported that work was difficult but possible at 0.15 to 0.2 ppm and that work was impossible at 0.3 ppm [Flury and Zernik 1931]. Exposures to 1 ppm have been reported to be highly irritating [Casarett 1975]. Eye irritation was experienced at 1.63 ppm after 2 minutes [ACGIH 1980]. It has been stated that iodine-containing materials appear to be more toxic than analogous bromine or chlorine-containing materials [ILO 1971]. The lethal oral dose has been reported to be 2 to 3 grams [Moore 1938]. [Note: An oral dose of 2 to 3 grams is equivalent to a worker being exposed to 126 to 190 ppm for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]

Revised IDLH: 2 ppm

Basis for revised IDLH: The revised IDLH for iodine is 2 ppm based on acute inhalation toxicity data in humans [ACGIH 1980]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 2 ppm. However, since it has been reported that iodine-containing materials are more toxic than bromine-containing materials, a revised IDLH of 2 ppm for iodine is appropriate since the revised IDLH for bromine is 3 ppm.


1. ACGIH [1980]. Iodine. In: Documentation of the threshold limit values. 4th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienist, p. 230.

2. Angelis L [1979]. Iopamidol. Drugs of the Future 4:876-881.

3. Casarett LJ [1975]. Toxicology of the respiratory system. In: Toxicology. The basic science of poisons. Casarett LJ, Doull J, eds. New York, NY: Macmillan, pp. 201-224.

4. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 309 (in German).

5. Flury F, Zernik F [1935]. Zusammenstellung der toxischen und letalen dosen für die gebräuchlichsten gifte und versuchstiere. Abder Hand Biol Arbeitsmethod 4:1289-1422 (in German).

6. ILO [1971]. Iodine. In: Encyclopaedia of occupational health and safety. 2nd ed. Vol. I (A-K). Geneva, Switzerland: International Labour Office, pp. 739-740.

7. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 76.

  1. Moore M [1938]. The ingestion of iodine as a method of attempted suicide. N Eng J Med 219:383-388.
Page last reviewed: December 4, 2014