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CHEMINFO Record Number: 510
CCOHS Chemical Name: Iodine

Elemental iodine

Chemical Name French: Iode
Chemical Name Spanish: Yodo
CAS Registry Number: 7553-56-2
RTECS Number(s): NN1575000
EU EINECS/ELINCS Number: 231-442-4
Chemical Family: Inorganic halogen compound / inorganic iodine compound / elemental iodine / molecular iodine
Molecular Formula: I2
Structural Formula: I-I


Appearance and Odour:
Solid iodine is greyish-black to purple with a metallic luster. It has a characteristic, irritating odour.

Odour Threshold:
No information available

Warning Properties:
Insufficient information for evaluation.

The information in this record applies only to elemental iodine. For information on specific iodine compounds, refer to individual CHEMINFO records.

Uses and Occurrences:
Ingredient in germicides, antiseptics and other medicinal preparations. In some areas, iodine is added to swimming and drinking water as a disinfectant. Also used as a reagent in research and analytical chemistry. In industry, iodine is used to prepare other iodine-containing compounds.



Effects of Short-Term (Acute) Exposure

Iodine vapour is a severe irritant (more irritating than the vapours of bromine or chlorine). Occupational reports indicate that concentrations of 0.1 ppm are tolerable, however work is difficult at 0.15 to 0.20 ppm and concentrations of 1 ppm are highly irritating.(5)
Symptoms include tightness in the chest, sore throat, and headache. Severe exposures result in symptoms such as airway constriction, shortness of breath, difficulty in breathing, accumulation of fluid in the lungs (pulmonary edema) and death.(5) The development of pulmonary edema could be delayed several hours.

Skin Contact:
Crystalline iodine or strong solutions of iodine are severe skin irritants. Iodine crystals can cause severe penetrating injury (corrosive tissue destruction) at the point of contact.
Solutions have caused crusting, burns (inflammatory reactions), skin eruptions (weeping) and fever. Individual susceptibility to such reactions shows great variation; some persons react after momentary contact with weak solutions, whereas others do not react after repeated contact with strong solutions.
In one case, death occurred following the application of an iodine tincture (iodine in alcohol solution) to one third of the body surface.(6)
Iodine is absorbed when applied to the skin.

Eye Contact:
Iodine can cause severe eye irritation or injury. Vapour concentrations of 0.57 ppm were tolerated for five minutes without eye irritation. However, a concentration of 1.63 ppm caused irritation in two minutes.(5)
Crystalline iodine or strong solutions of iodine can probably cause severe eye irritation and permanent damage.

Swallowing iodine can cause burning and pain in the mouth, throat and stomach, corrosion (destruction) of tissues lining the mouth, esophagus and stomach, severe vomiting, thirst, metallic taste, diarrhea, shock, fever, anuria, delirium, stupor and death from kidney failure.
If there is food present in the stomach it can react with iodine to form iodides which are relatively harmless in an acute exposure.(6)

Effects of Long-Term (Chronic) Exposure

No human information, but chronic effects are unlikely because acute effects are so severe.

INGESTION: Prolonged ingestion of iodine or iodine compounds can lead to iodism: typical symptoms include bronchitis and laryngitis; redness, swelling and open sores on the skin, eyes and mouth; weight loss, sleepiness and nervous symptoms. Symptoms normally disappear quickly when exposure ceases.

SKIN SENSITIZATION: A solution of iodine and potassium iodide (iodophor) caused an allergic response in 9 of 25 volunteers.(16) The identity of the sensitizing agent is not known, but iodine solutions are recognized sensitizing agents.(6,16)


Animal data indicates iodine is not carcinogenic. No human information is available.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

ACGIH has proposed a carcinogenicity designation of A4 (not classifiable as a human carcinogen).

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
No information available

Reproductive Toxicity:
No information available

No information available

Toxicologically Synergistic Materials:
None reported

Potential for Accumulation:
Iodine breaks down rapidly in the body. Iodine compounds (iodides) are concentrated in the thyroid gland. Iodides accumulate when exposure exceeds body needs. Excess iodides are cleared from the body within a few days when exposure ceases.

Health Comments:
The toxic effects attributed to radioactive iodine isotopes are due to the radiation rather than the iodine.


If airborne concentrations are irritating, take proper precautions to ensure your own safety before attempting rescue; e.g., wear appropriate protective equipment, use the "buddy" system. Remove source of contamination or move victim to fresh air. Oxygen may be beneficial if administered by a person trained in its use, preferably on a physician's advice. Obtain medical attention immediately.

Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective gloves, if necessary. As quickly as possible, flush contaminated area with lukewarm, gently running water for at least 20 minutes, by the clock. Under running water, remove contaminated clothing, shoes, and leather goods (e.g., watchbands, belts). If irritation persists, obtain medical attention immediately. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for up to 60 minutes, by the clock, holding the eyelid(s) open. Take care not to rinse contaminated water into the non-affected eye. If irritation persists, repeat flushing. Obtain medical attention immediately.

Never give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, have victim lean forward to reduce risk of aspiration. Repeat administration of water. Obtain medical attention immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a physician and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a physician and appropriate delegation of authority obtained, as required.

All first aid procedures should be periodically reviewed by a physician familiar with the material and its conditions of use in the workplace.


Flash Point:
Not applicable. Will not burn.

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Iodine alone is not sensitive to mechanical shock, however it does react with ammonia to form compounds sensitive to mechanical shock.

Sensitivity to Static Charge:
Not applicable

Combustion and Thermal Decomposition Products:
None reported. Iodine vapours are extremely toxic and irritating.

Fire Hazard Summary:
Will not burn. However, iodine can react vigorously with certain reducing materials causing fire and explosion hazards. As well, high temperatures can sublime iodine releasing highly irritating vapours.

Extinguishing Media:
Iodine will not burn. Use extinguishing media appropriate for surrounding material.

Fire Fighting Instructions:
Iodine will not burn or react with water. Use fire fighting procedures appropriate for surrounding material.


Molecular Weight: 253.80

Conversion Factor:
1 ppm = 10.4 mg/m3; 1 mg/m3 = 0.097 ppm at 20 deg C

Melting Point: 114 deg C (236 deg F)
Boiling Point: 184 deg C (363 deg F)
Relative Density (Specific Gravity): 4.93 (water = 1)
Solubility in Water: Extremely low solubility (0.03 g/100 mL at 20 deg C). Solubility increases with increasing temperature.
Solubility in Other Liquids: Very soluble in benzene (16 g/100 g), ethyl ether (34 g/100 g), ethyl alcohol (27 g/100 g); moderately soluble in cyclohexane (3 g/100 g) and a number of other organic solvents.
Coefficient of Oil/Water Distribution (Partition Coefficient): Not available
pH Value: Not applicable
Vapour Density: 8.75 (air = 1)
Vapour Pressure: 0.3 mm Hg at 20 deg C (5,11)
Saturation Vapour Concentration: 400 ppm at 20 deg C (calc)
Evaporation Rate: Not available
Critical Temperature: 512 deg C



Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

AMMONIA (gaseous) and AMMONIUM HYDROXIDE (solution) - can form nitrogen iodide which is sensitive to shock and may explode spontaneously.

BASIC AMMONIUM SALTS - can react to form explosive nitrogen iodide.

ACETYLENE - reacts explosively.

CHLORINE (liquid) - reacts violently.

SODIUM PHOSPHINATE (anhydrous) - reacts in a violent, exothermic manner, causing ignition.

ANTIMONY - can produce a reaction generating heat, flame and even explosion if the quantities are great enough.

PHOSPHOROUS (white or yellow) - at ordinary temperatures, this will unite with iodine to produce a spontaneously flammable product. Red phosphorous does not react at ordinary temperatures.

ACTIVE METALS (lithium, magnesium) - can react violently.

REDUCING MATERIALS (sulfur, iron, alkali metals) - react violently.

OILS (turpentine) - can form explosive mixtures.

Hazardous Decomposition Products:
Not reported

Corrosivity to Metals:
Iron and steel are corroded under most conditions. Copper alloys are corroded at elevated temperatures.(11,15)


EYE IRRITATION: Application of 2% solution of iodine in alcohol to rabbit eyes caused some damage which was reversible. A stronger solution (7% iodine) caused severe damage to rabbit and monkey eyes.(4)
Injection of an alcoholic solution of iodine into the eyes of dogs caused severe damage.(4)

ORAL TOXICITY: Values commonly reported for "iodine" are actually for iodine compounds and are not relevant. Values for elemental iodine were not found.
Iodine has a direct action on cells by precipitating proteins. The affected cells may be killed. The effects of iodine are thus similar to those produced by strong acids.

ACUTE INHALATION EXPOSURES: Dogs were exposed by inhalation (intratracheal) to vapours of iodine. Doses as low as 7-12 mg/kg caused inflammation of the lungs, breathing problems and coughing which persisted for weeks. Doses of 14-18 mg/kg caused fluid accumulation in the lungs (pulmonary edema) and death within 24 hours.(2)
In another study, iodine vapour at low concentrations (0.5 ppm) did not cause any detectable effects in guinea pigs. However, as the concentration of iodine was increased (up to 7 ppm), the breathing capacity of the guinea pigs was impaired.(3)

CARCINOGENICITY: There is limited animal data indicating that iodine is not carcinogenic. Application of solutions of 5-10% iodine to the skin of mice did not produce a carcinogenic effect.(9) In another study with hamsters, intratracheal administration of iodine (0.2 mg) along with benzo(a)pyrene increased the total number of tumours in comparison to hamsters given only benzo(a)pyrene. However, iodine on its own was not carcinogenic.(8)


Selected Bibliography:
(1) RTECS record for iodine. Last updated 8804; printed 1988 11 18
(2) Luckhardt, A.B., et al. The physiological action of the fumes of iodine. The Journal of Pharm. and Exper. Therap. Vol. XV. no. 1 (1920). p. 1-21
(3) Amdur, M.O. Respiratory response to iodine vapor alone and with sodium chloride aerosol. Journal of Toxicology and Environmental Health. Vol. 4 (1978). p. 619-630
(4) Grant, W.M. Toxicology of the eye. 3rd ed. Charles C. Thomas, 1986. p. 519-520
(5) Documentation of the threshold limit values and biological exposure indices. 5th ed. ACGIH, 1986. p. 323
(6) Gosselin, R.E., et al. Clinical toxicology of commercial products. 5th ed. Williams & Wilkins, 1984. p. III-213 - III-214
(7) Finkelstein, R., et al. Fatal iodine poisoning : a clinico-pathologic and experimental study. Ann. Internal Med. Vol. 10 (1937). p. 1283-1296
(8) Stenback, F., et al. Carcinogenic activation of benzo(a)pyrene by iodine and ferric chloride in the respiratory tract of Syrian golden hamsters. Experientia. Vol. 34 (1978). p. 1065-1066
(9) Rosenstirn, J. Iodine irritation does not produce cancer. J. Cancer Research. Vol. 10 (April 1926). p. 61-65
(10) HSDB record for iodine. Complete update on 07/12/88; printed 1988 11 18
(11) Kirk-Othmer encyclopedia of chemical technology. Vol. 13. 3rd ed. John Wiley & Sons, 1981. p. 649-677
(12) NIOSH pocket guide to chemical hazards. NIOSH, June 1994. p. 172-173
(13) Patty's industrial hygiene and toxicology. 3rd rev. ed. Vol. 2B. John Wiley & Sons, 1981. p. 2972-2978
(14) Fire protection guide on hazardous materials. 9th ed. National Fire Protection Association, 1986. p. 110-111
(15) Corrosion data survey : metals section. 6th ed. NACE, 1985. p. 72-73
(16) Kligman, A.M. The identification of contact allergens by human assay. The Journal of Investigative Dermatology. Vol. 47, no. 3 (1966). p. 393-409
(17) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(18) European Communities. Commission Directive 98/98/EC. December 15, 1998

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1989-09-29

Revision Indicators:
PEL-C 1993-03-01
Trans PEL comments 1993-04-01
TDG 1994-02-01
Sampling 1996-05-01
EU number 1996-05-01
US transport 1996-05-01
Respiratory guidelines 1996-05-01
Resistance of materials 1998-05-01
Bibliography 1998-05-01
EU Class 2000-04-01
EU Risk 2000-04-01
EU Safety 2000-04-01
Bibliography 2000-04-01
ERPG 2001-03-01
Carcinogenicity 2003-07-24
PEL-C final 2003-10-28
PEL transitional comments 2003-10-28
PEL-TWA final 2003-10-28
Resistance of materials for PPE 2004-03-28

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