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CHEMINFO Record Number: 224
CCOHS Chemical Name: Ethyl isocyanate

Isocyanic acid, ethyl ester

Chemical Name French: Isocyanate d'éthyle
CAS Registry Number: 109-90-0
UN/NA Number(s): 2481
RTECS Number(s): NQ8825000
EU EINECS/ELINCS Number: 203-717-9
Chemical Family: Isocyanic acid ester / isocyanate / aliphatic isocyanate / monoisocyanate / aliphatic monoisocyanate
Molecular Formula: C3-H5-N-O
Structural Formula: CH3-CH2-N=C=O


Appearance and Odour:
Colourless liquid with pungent odour; lachrymator (vapour irritates the eyes and causes tears).(8)

Odour Threshold:
No information available

Warning Properties:
Information not available for evaluation.

Uses and Occurrences:
Monoisocyanates are used as chemical intermediates in the production of drugs, pesticides, amines, ureas and other carbamoyl compounds.


Colourless liquid, with a pungent odour. Lachrymator. EXTREMELY FLAMMABLE LIQUID AND VAPOUR. Vapour is heavier than air and may spread long distances. Distant ignition and flashback is possible. Can decompose at high temperatures forming toxic gases, such as nitrogen oxides and hydrogen cyanide. Closed containers may develop pressure and rupture on prolonged exposure to heat. Reacts violently with water. May polymerize if heated or in contact with water. TOXIC. May be fatal if inhaled or swallowed. Vapour is probably extremely irritating to the eyes and respiratory tract. May cause lung injury--effects may be delayed. Liquid causes skin and eye irritation.


Effects of Short-Term (Acute) Exposure

Ethyl isocyanate is a very strong irritant and initial injury is probably confined to areas of direct contact such as the nose, mouth and respiratory tract. Very serious and persistent respiratory system and lung damage may occur which can result in death. The toxicity of ethyl isocyanate is similar to that of methyl isocyanate.(1)
Typical symptoms include breathlessness, dry cough, throat irritation or choking, chest pain/tightness, difficulty in breathing and possibly coughing up blood. Other common symptoms include lethargy, loss of appetite, convulsions and coma.(1) Symptoms may appear immediately or may be delayed several hours after exposure, depending upon the concentration, and may continue for 3 to 7 days or longer. Permanent lung damage may result. Inhalation of very high levels might cause chemical bronchitis with asthma-like wheezing and can be fatal due to severe respiratory tract and lung damage (pulmonary edema).
There are currently no reports of effects in people working with ethyl isocyanate.

Skin Contact:
The liquid can cause severe skin irritation, redness, blistering (edema) and possibly tissue death (necrosis). There is no human information but it caused severe skin irritation in laboratory animals.(1)
Like other isocyanates, ethyl isocyanate may cause skin sensitization, although there are no reports of this happening and negative results were obtained in one series of animal tests.

Eye Contact:
The liquid can cause very severe eye injury and severe permanent eye damage (tissue death). There are no reports of human exposure but it caused severe permanent eye injury in laboratory animals.(1)
Exposure to the vapour can cause irritation with tearing. Very high concentrations could result in severe eye injury, including intense burning of the eyes, and corneal ulcerations. In most cases, the effects are expected to be temporary.

There have been no reports of people ingesting ethyl isocyanate and ingestion is unlikely to occur in the workplace. Ingestion would probably cause severe irritation of the mouth, throat and digestive tract. Ethyl isocyanate has been shown to be toxic in an animal study.

Effects of Long-Term (Chronic) Exposure

Lungs/Respiratory System:
Ethyl isocyanate is expected to be a severe respiratory irritant, based on comparison to closely related monoisocyanates. Long-term, low-level exposure could cause severe, permanent respiratory impairment.

Exposure to isocyanates is likely to aggravate individuals with existing respiratory disease, such as chronic bronchitis, and emphysema.

Respiratory Sensitization:
Some isocyanates are well known to cause respiratory sensitization. However, there are no reports of ethyl isocyanate or other monoisocyanates causing respiratory sensitization.
Isocyanate respiratory sensitization is usually caused by a very large exposure, or by multiple exposures. Although varying periods of exposure (1 day to years) may elapse before sensitization occurs, it develops more often during the first few months of exposure. Sensitized indivduals react to low levels of airborne isocyanates that have no effect on unsensitized people.(2)
Cross-sensitization between different isocyanates may occur.(3)

Skin Sensitization:
There have been no reports of ethyl isocyanate causing skin sensitization in humans. Ethyl isocyanate did not cause skin sensitization in one animal study.(5) Other isocyanates are skin sensitizers.


There is no human or animal information.

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 no listing for this chemical.

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

Teratogenicity and Embryotoxicity:
There is no human or animal information.

Reproductive Toxicity:
There is no human or animal information.

No human or animal in vivo studies are available. Ethyl isocyanate was positive in a bacterial (Ames) test.(7)

Toxicologically Synergistic Materials:
Insufficient information

Potential for Accumulation:
Probably does not accumulate. Reacts with water and tissues to form ethylamine.


If symptoms are experienced, remove source of contamination or move victim to fresh air and obtain medical advice. This product is flammable. Take proper precautions (e.g. remove any sources of ignition). Take proper precautions to ensure your own safety before attmepting rescue (e.g. wear appropriate protective equipment, use the buddy system). Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by trained personnel, preferably on a doctor's advice. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. Immediately transport victim to an emergency care facility.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. Quickly and gently blot or brush away excess chemical. Wash gently and thoroughly with water and non-abrasive soap for 20 minutes or until chemical is removed. Under running water, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Obtain medical attention immediately. Discard contaminated clothing, shoes and leather goods.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Quickly and gently blot or brush away excess chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, or until the chemical is removed while holding the eyelid(s) open. Take care not to rinse contaminated water into non-affected eye. 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 to dilute material in stomach. Obtain medical attention immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except under 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 doctor and appropriate delegation of authority obtained, as required.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
-6 deg C (20 deg F) (closed cup) (8,9)

Lower Flammable (Explosive) Limit (LFL/LEL):
Information not available

Upper Flammable (Explosive) Limit (UFL/UEL):
Information not available

Autoignition (Ignition) Temperature:
Information not available

Sensitivity to Mechanical Impact:
Insufficient information. Probably not sensitive, since it is a stable material.

Sensitivity to Static Charge:
Insufficient information. Ethyl isocyanate vapours in the flammable range may be ignited by a static discharge.

Combustion and Thermal Decomposition Products:
Nitrogen oxides, hydrogen cyanide.(9)

Fire Hazard Summary:
Extremely flammable. Material will readily ignite at room temperature. Vapour is heavier than air and may travel a considerable distance to a source of ignition and flash back to a leak or open container. During a fire, irritating/toxic nitrogen oxides and hydrogen cyanide may be generated. Vapour may cause death if it penetrates the firefighter's normal protective gear. Reacts violently with water. Can accumulate in confined spaces, resulting in an explosion and toxicity hazard. Closed containers may rupture violently when heated.

Extinguishing Media:
Dry chemical powder, carbon dioxide, protein foam. Water spray or fog may be used for cooling. Water-based extinguishers and foams should not be used on ethyl isocyanate since the reaction is violent.(8)

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
Stop leak before attempting to stop the fire. If the leak cannot be stopped, and if there is no risk to the surrounding area, let the fire burn itself out. If the flames are extinguished without stopping the leak, vapours could form explosive mixtures with air and reignite.
If possible, isolate materials not yet involved in the fire. Closed containers or tanks may explode in the heat of the fire. Move containers from fire area if this can be done without risk. Otherwise, keep fire-exposed tanks or containers cool by application of hose streams. Application of cooling streams should begin as soon as possible. If this is not possible, set up unmanned monitor nozzles and evacuate the area. Take care not to get water inside containers.
Ethyl isocyanate can react violently with water and water-based fire extinguishers. Water can be used as a spray or fog to absorb heat and protect exposed material of structures. If a leak or spill has not ignited, use water spray in large quantities to disperse the vapours and to protect personnel attempting to stop a leak. However, proper care must be taken because of the violent reaction between water and ethyl isocyanate.
After the fire has been extinguished, the area should not be considered safe until a thorough inspection for residual isocyanate has been carried out by properly protected personnel.
Ethyl isocyanate and its decomposition products, such as hydrogen cyanide and nitrogen oxides, are extremely hazardous to health. Do not enter fire area without specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. A full-body encapsulating chemical suit with positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 71.09

Conversion Factor:
1 ppm = 2.9 mg/m3; 1 mg/m3 = 0.345 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: Less than -50 deg C (-58 deg C) (8)
Boiling Point: 60 deg C (140 deg F) (1,8,9)
Relative Density (Specific Gravity): 0.898 at 20 deg C (water = 1) (9)
Solubility in Water: Insoluble. Reacts with water.(8)
Solubility in Other Liquids: Soluble in ethyl alcohol, diethyl ether and chlorinated and aromatic hydrocarbons.
Coefficient of Oil/Water Distribution (Partition Coefficient): Not applicable (reacts with water).
pH Value: Not applicable (reacts with water)
Vapour Density: 2.45 (air = 1)
Vapour Pressure: 2.33 kPa (17.5 mm Hg) at 24 deg C.(1) Also reported as 1.73 kPa (13 mm Hg) at 22.8 deg C.(9)
Saturation Vapour Concentration: 230,300 ppm (23%) at 24 deg C; 17108 ppm (1.71%) at 22.8 deg C (calculated)
Evaporation Rate: Not available
Critical Temperature: Not available


Normally stable. It self-reacts at elevated temperatures to form trimers and polymers giving off carbon dioxide and heat.(11)

Hazardous Polymerization:
Ethyl isocyanate may undergo uncontrolled exothermic trimerization and polymerization upon contact with incompatible materials, such as trialkyl phosphines, triphenylarsenic oxide, potassium acetate and many metal compounds soluble in organic media, such as organotin compounds, or if heated.(11) The heat and products generated from this reaction can result in a pressure build-up in closed containers that is sometimes sufficient to rupture the container.

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.

WATER - Reacts vigorously or violently, forming carbon dioxide gas and diethylurea. The reaction may become progressively more vigorous at higher temperatures.(8,11) Closed containers can rupture explosively when contaminated with water.
STRONG OXIDIZING AGENTS - May react violently with the risk of fire and explosion.(8,9)
ALCOHOLS, ACIDS, BASES, AMINES - May react vigorously or violently with the risk of fire and explosion.(8,9)
CERTAIN CATALYSTS (e.g. triphenylarsenic oxide and tributyl tin oxide) - may cause a violent reaction.(11)

Hazardous Decomposition Products:
Ethylamine (formed by reaction of ethyl isocyanate with water)

Conditions to Avoid:
Sparks, open flames, electrostatic discharge, heat, other ignition sources, moisture.

Corrosivity to Metals:
Information not available

Stability and Reactivity Comments:
Isocyanates are very reactive compounds and are especially highly reactive toward a large number of compounds with active hydrogens, particularly at high temperatures and in the presence of catalysts.(11,10) See references 11 and 10 for some of the reactions of isocyanates.


LD50 (oral, rat): approximately 230 mg/kg (10% in corn oil) (6)
A sufficient number of animals was used with dosage levels limited to a narrow range so that the dose indicated represents a fairly accurate LD50.(6)

Eye Irritation:

Ethyl isocyanate caused severe permanent eye injury in laboratory animals (probably rabbits).(1)

Skin Irritation:

Ethyl isocyanate caused severe skin irritation in laboratory animals (probably rabbits).(1)

Skin Sensitization:
Ethyl isocyanate did not cause skin sensitization in one test series with guinea pigs.(5)


Selected Bibliography:
(1) Woolrich, P.F. Monoisocyanates, diisocyanates and polyisocyanates: engineering, medical control and toxicologic considerations. Technical bulletin 106. The Upjohn Company, 1973
(2) Karol, M.H. Respiratory effects of inhaled isocyanates. CRC Critical Reviews in Toxicology. Vol. 16, issue 4 (1986). p. 349-379
(3) Musk, A.W., et al. Isocyanates and respiratory disease: current status. American Journal of Industrial Medicine. Vol. 13, no. 3 (1988). p. 331-349
(4) RTECS record for isocyanic acid, ethyl ester. Date of last update: 9404
(5) Rao, K.S., et al. A collection of guinea pig sensitization test results -- grouped by chemical class. Drug and Chemical Toxicology. Vol. 4, no. 4 (1981). p. 331-351
(6) Toxicity and safe handling of isocyanates: a review of the literature (TDI) and results of toxicity screening studies on additional compounds. Mobay Chemical Corporation, [n.d.]
(7) Yamaguchi, T. Mutagenicity of isothiocyanates, isocyanates and thioureas on Salmonella typhimurium. Agricultural and Biological Chemistry. Vol. 44, no. 12 (1980). p. 3017-3018
(8) Chemical safety sheets: working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 421
(9) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 1627D
(10) HSDB record for ethyl isocyanate. Date of last update: 9010
(11) Kirk-Othmer encyclopedia of chemical technology. 3rd. edition. Vol. 13. John Wiley and Sons, 1981. p. 789-818

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: 1995-03-07

Revision Indicators:
Chronic exposure 1995-05-01
Extinguishing media 1995-05-01
Fire fighting instructions 1995-05-01
Sampling 1995-11-01
Respiratory guidelines 1995-11-01
EU class 1995-11-01
US transport 1998-03-01
Resistance of materials 1998-06-01
Bibliography 1998-06-01
Vapour pressure 2004-09-15

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