Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content


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(mg/kg) LDLo(mg/kg) Adjusted LD Derived value



Angelis 1979Angelis 1979

Angelis 1979

Flury and Zernik 1935










9,289 ppm14,597 ppm

6,635 ppm

531 ppm

929 ppm1,460 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 ppmBasis 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.