Acetonitrile (CH₃CN) is the simplest organic nitrile. It is a colourless liquid that mixes easily with water and most organic solvents like alcohols, acetone, ether, and benzene. However, it does not mix well with petroleum ether or saturated hydrocarbons.
It is made mainly as a by-product during the production of acrylonitrile.
Acetonitrile can be dangerous — it reacts with acids, bases, oxidising agents, and water to produce toxic fumes and flammable vapours. When burned, it releases hydrogen cyanide and nitrogen oxides, both of which are toxic. It can also damage plastics, rubber, and coatings.
What is Acetonitrile used for?
Acetonitrile is widely used in:
Pharmaceutical manufacturing (as a solvent)
Plastic casting and moulding
Fibre spinning
Lithium batteries
Extracting fatty acids from oils
Chemical analysis, such as detecting pesticide residues in labs
Textile dyeing and coating applications
As a stabiliser for chlorinated solvents
As an intermediate in making perfumes
Acetonitrile is widely used in plastic casting and moulding.
Sources and Routes of Exposure
Sources of Exposure
Acetonitrile can enter the environment from:
Factories and industrial plants
Car exhaust
Evaporation from water sources
People may be exposed by:
Breathing contaminated air
Smoking or being near smokers
Skin contact, especially in workplaces
Routes of Exposure
The main ways acetonitrile enters the body are
Inhalation of vapours
Skin contact — it absorbs quickly through the skin
Eye contact
Ingestion is rare but possible
Health Effects
Acute Effects
Inhaling up to 500 ppm of acetonitrile can cause:
Irritation of mucous membranes
At higher levels: weakness, nausea, convulsions
Animal testing has shown:
Moderate to high toxicity when swallowed
Moderate toxicity when inhaled
Chronic Effects
Long-term exposure can lead to cyanide poisoning, since the body converts acetonitrile into cyanide after it's absorbed. Health effects may include:
Headaches, numbness, tremors (CNS symptoms)
Skin contact may cause dermatitis
Cyanide poisoning can also result from swallowing or skin exposure
Animals show different levels of sensitivity to acetonitrile, depending on the species.
The EPA Reference Concentration (RfC) is 0.06 mg/m³, based on mouse studies.
No Reference Dose (RfD) has been established by the EPA.
Reproductive and developmental Effects
No human data is available.
In animal studies, acetonitrile exposure has been linked to:
Lower foetal body weight
More birth defects
Cancer Risk
No strong evidence in humans.
A 2-year study by the National Toxicology Programme (NTP) found:
Equivocal (uncertain) evidence of cancer in male rats
No evidence in female rats or mice
The EPA classifies acetonitrile as Group D – not classifiable for human cancer risk
In animal studies:
Mice exposed by inhalation showed kidney and mammary (breast) tumours
Rats exposed through drinking water showed adrenal gland tumours
However, a study by the National Toxicology Program (NTP) did not find increased tumours in rats or mice when the chemical was given orally (by gavage)
The EPA has assigned an oral cancer slope factor of 0.6 (mg/kg/day)⁻¹, which is used to estimate cancer risk from long-term exposure.
Safety
First Aid Measures
Eye Contact:
Remove contact lenses if present.
Rinse eyes with running water for at least 15 minutes, keeping eyelids open.
You may use cold water.
Get medical attention immediately.
Skin Contact:
Rinse skin thoroughly with plenty of water for at least 15 minutes while removing contaminated clothing and shoes.
Apply an emollient (soothing lotion) if skin is irritated.
Wash clothing before reuse and clean shoes thoroughly.
Get medical attention immediately.
Serious Skin Contact:
Wash with disinfectant soap and apply anti-bacterial cream.
Seek immediate medical help.
Inhalation:
Move the person to fresh air.
If not breathing, give artificial respiration.
If breathing is difficult, give oxygen.
Seek immediate medical attention.
Serious Inhalation:
Evacuate to a safe area as quickly as possible.
Loosen tight clothing (collars, belts, etc.).
Use oxygen if breathing is difficult.
Only perform mouth-to-mouth resuscitation if it’s safe, as the chemical may be toxic.
Seek immediate medical attention.
Ingestion:
Do not induce vomiting unless directed by medical personnel.
Never give anything by mouth to someone who is unconscious.
Loosen tight clothing.
Get medical help immediately.
Fire Hazard
Highly flammable in the presence of flames, sparks, heat, and oxidisers
For small fires: Use dry chemical powder
For large fires: Use alcohol-resistant foam, water spray, or fog
Exposure Control & Personal Protection
Engineering Controls
Use exhaust ventilation to keep vapour levels below the safe limit.
Make sure eyewash stations and safety showers are close to where the chemical is handled.
Personal Protective Equipment (PPE)
When working with acetonitrile, use
Splash goggles
Lab coat
Chemical-resistant gloves
Approved vapour respirator
In case of a large spill, additional PPE includes:
Full protective suit
Boots
Self-contained breathing apparatus (SCBA)
Always consult a safety specialist to ensure that protective gear is suitable for your situation.
Regulation
Exposure Limits
United States
OSHA: The Occupational Safety & Health Administration has established a Permissible Exposure Limit (PEL) for acetonitrile of 40 ppm, 70 mg/m3 TWA
ACGIH: The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) is 20 ppm, 34 mg/m3 TWA; Skin; Appendix A4 - Not Classifiable as a Human Carcinogen
NIOSH: The National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) is 20 ppm, 34 mg/m3 TWA
Australia
Safe Work Australia: Safe Work Australia has established an exposure standard for acetonitrile of 40 ppm (equivalent to 67 milligram/m3) (TWA). The short-term exposure level (STEL) is 60 ppm (equivalent to 101 milligram/m3). Safe Work Australia also issued a skin absorption notice, which indicates that absorption through the skin may be a significant source of exposure.
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