Acetaldehyde is primarily used as an intermediate in the manufacture of a range of chemicals, perfumes, aniline dyes, plastics and synthetic rubber and in some fuel compounds. Acetaldehyde is also used in the manufacture of disinfectants, drugs, perfumes, explosives, lacquers and varnishes, photographic chemicals, phenolic and urea resins, rubber accelerators and antioxidants, and room air deodourisers. It is also used as a synthetic flavouring substance, food preservative and as a fragrance.
Substance name: Acetaldehyde
CASR number: 75-07-0
Molecular formula: C2H4O
Synonyms: Ethanal; ethyl aldehyde; acetic aldehyde; aldehyde; acetylaldehyde; aldehyde acetic aldehyde, NCI-C56326, RCRA waste number U001, UN 1089.
Clear colourless fuming liquid with a pungent, fruity odour. Vapours are heavier than air and can travel considerable distances and cause flash back from combustion sources. When heated to decomposition it emits acrid smoke and toxic fumes of carbon monoxide and carbon dioxide.
Specific Gravity: 0.778 @ 20°C
Melting Point: -123.5°C
Boiling Point: 21°C
Vapour pressure: 400 mm Hg @ 4.9°C : 760 mm Hg @ 20.2°C
Flash point: -40°C
100% volatile by volume.
This chemical is dangerous when exposed to heat or flame. It is sensitive to air and may undergo autopolymerization. It is also sensitive to moisture. Upon prolonged storage, it may form unstable peroxides. Can react vigorously with acid anhydrides, alcohols, ketones, phenols, ammonia, hydrogen cyanide, hydrogen sulfide, halogens, amines phosphorous, isocyanates, strong alkalies and strong acids and is incompatible with oxidising and reducing agents. It also reacts with nitric acid, peroxides, caustic soda and soda ash. Reactions with cobalt chloride, mercury(II)chlorate or mercury(II)perchlorate form sensitive and explosive products. Polymerisation may occur with acetic acid. Autoignition of vapour may occur on contact with corroded metals. Exothermic polymerisation can occur with trace metals. It is miscible with gasoline, naptha, xylene, turpentine, ether, benzene and alcohol. Rubber products decompose on contact with acetaldehyde, but it is not corrosive to most metals.
The National Pollutant Inventory (NPI) holds data for all sources of acetaldehyde emissions in Australia.
Acetaldehyde is an irritant of the skin, eyes, mucous membranes, throat and respiratory tract. Symptoms of exposure to this compound include nausea, vomiting, headache, dermatitis and pulmonary oedema (fluid in the lungs). These effects may be delayed. It has a general narcotic action and large doses cause death by respiratory paralysis. It may also cause drowsiness, delirium, hallucinations and loss of intelligence. Exposure may also cause slow mental response, severe damage to the mouth, throat and stomach; accumulation of fluid in the lungs, chronic respiratory disease, kidney and liver damage, throat irritation, dizziness, reddening and swelling of the skin and sensitisation. It may cause photophobia. Liquid splashed in the eyes may cause a burning sensation, lacrimation and blurred vision. It may also cause transient conjunctivitis.
Acetaldehyde is a substance which may reasonably be anticipated to be a carcinogen.
Entering the body
Exposure to acetaldehyde is primarily through breathing though skin absorption and ingestion are also possible.
Principal human exposure will be from inhalation of ambient air from urban areas or near sources of combustion. The greatest potential for exposure is to workers in the organic chemicals industry, with some exposure in fabricated rubber products and biological products industries. Potential exposure exists for personnel involved in the manufacturing or use of industrial organic chemicals, dyes, fabricated rubber, plastics, urea-formaldehyde foam insulation, fuels, drugs, explosives, lacquers and varnishes, photographic chemicals, pesticides, food additives, leather goods, and mirrors. Acetaldehyde is a potential exposure problem for automobile and diesel mechanics, petrol station attendants, and agricultural and food industry personnel, as well as personnel in coffee-roasting operations, lithographic coatings, automobile spray operations, and fat-rendering plants. In general, concentrations are higher indoors than outdoors due, in part, to the abundance of combustion sources such as cigarettes and fireplaces. Acetaldehyde can be emitted from cooking hamburgers, and from some building materials such as rigid polyurethane foams, and some consumer products such as adhesives, coatings, lubricants, inks, and nail polish remover. Other potential sources of indoor acetaldehyde concentrations are the infiltration of vehicle exhaust and the evaporation of acetaldehyde from certain foods.
Workplace Exposure Standards
Safe Work Australia sets the workplace exposure standard for acetaldehyde through the workplace exposure standards for airborne contaminants:
- Maximum eight hour time weighted average (TWA): 20 parts per million (36 mg/m3)
- Maximum short term exposure limit (STEL): 50 parts per million (91 mg/m3).
These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
Drinking water guidelines
There is no guideline for acetaldehyde in the Australian Drinking Water Guidelines.
In sufficient concentrations acetaldehyde can effect animals in a similar way to humans.
Entering the environment
Because acetaldehyde rapidly evaporates it most likely to be transported in air though it degrades rapidly and is therefore unlikely to be transported far.
Where it ends up
It will rapidly evaporate from water or land. In the atmosphere, acetaldehyde will degrade in a matter of hours by photochemical oxidation and reaction with hydroxyl radicals. It can leach into the ground. It degrades readily in soil, sewage, and natural waters.
Sources of emissions
The use of acetaldehyde is widespread in industry, and it may be released into waste water or the air during production, use, transportation and storage. Sources of acetaldehyde include fuel combustion emissions from stationary internal combustion engines and power plants that burn fossil fuels, wood, or trash, oil and gas extraction, refineries, cement kilns, lumber and wood mills and paper mills.
Diffuse sources and industry sources included in diffuse emissions data
Production by photochemical oxidation of other compounds in the air is the largest source of acetaldehyde concentrations in the ambient air. Acetaldehyde is emitted from residential fireplaces and wood stoves, bush fires, and agricultural burning.
Acetaldehyde has a widespread natural occurrence. Acetaldehyde occurs in nature as an intermediate product in the respiration of higher plants and can be found in ripening fruit such as apples. Also, acetaldehyde is an intermediate product of fermentation of alcohol and in metabolism of sugars in the body. It may form in wine and other alcoholic beverages after exposure to air. It naturally occurs as a result of forest fires, volcanoes, animal wastes, and insects. It is a volatile component of cotton leaves and blossoms. Acetaldehyde occurs in oak and tobacco leaves and is a natural component of apples, broccoli, coffee, grapefruit, grapes, lemons, mushrooms, onions, oranges, peaches, pears, pineapples, raspberries, and strawberries. It has been detected in the essential oils of alfalfa, rosemary, balm, clary sage, daffodil, bitter orange, camphor, angelica, fennel, mustard, and peppermint.
Acetaldehyde is present in automobile and diesel exhaust.
Consumers may be exposed to acetaldehyde in cheese, heated milk, cooked beef, cooked chicken, and rum. It is an important component of food flavourings (in low concentrations which are generally recognised as safe) and is added to milk products, baked goods, fruit juices, sweets, desserts, and soft drinks. It is an especially useful for imparting orange, apple, and butter flavours. It is used in the manufacture of vinegar and yeast and as a fruit and fish preservative. Consumers may have been exposed to acetaldehyde in room air deodorisers. Exposure in the home environment may occur from the products of burning wood in stoves or fire places.
Sources used in preparing this information
- Chemfinder by Cambridgesoft (accessed May 1999)
- US Environmental Defense Fund Scorecard (accessed May 1999)
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council
- US National Safety Council Environmental Health Centre Chemical Backgrounder Index (accessed May 1999)
- US National Toxicology Program (accessed May 1999)
- USEPA Integrated risk Information System (accessed May 1999)
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed June 2021.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018