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CHEMINFO Record Number: 715
CCOHS Chemical Name: Acetaldehyde

Acetic aldehyde
Ethyl aldehyde

Chemical Name French: Acétaldéhyde
Chemical Name Spanish: Acetaldehido
CAS Registry Number: 75-07-0
UN/NA Number(s): 1089
RTECS Number(s): AB1925000
EU EINECS/ELINCS Number: 200-836-8
Chemical Family: Saturated aliphatic aldehyde / saturated aliphatic monoaldehyde / alkanal / ethanal
Molecular Formula: C2-H4-O
Structural Formula: CH3-C(=O)-H


Appearance and Odour:
Highly volatile, colourless liquid (at temperatures below 20.2 deg C) with a penetrating, pungent, suffocating odour that is somewhat fruity and quite pleasant in low concentrations.(9,31,32)

Odour Threshold:
A wide range of values has been reported: 0.0028 to 1000 ppm. An acceptable, critiqued value is 0.067 ppm (detection).(33) Another source reports the geometric value of all published values as 0.05 ppm.(9,34)

Warning Properties:
GOOD - TLV is approximately 500 times the odour threshold.

Commercial acetaldehyde has a minimum purity of 99%. It is also available as a 50% solution in water and a 50 wt.% solution in ethanol.(31,35,36) Acetaldehyde is a gas at 20.2 deg C. However, it is stored and transported as a liquid in glass pressure bottles, stainless steel or equivalent phenolic-resin lined drums, or insulated tank cars. It is used in refrigerated or chilled processes. Therefore, it is normally encountered in the workplace as a highly volatile liquid.

Uses and Occurrences:
Acetaldehyde is used mainly as a chemical intermediate in the production of acetic acid. It is also used to produce many other chemicals. It is used in the manufacture of paraldehyde, metaldehyde, other polymers, plastics, synthetic rubber and resins, cosmetics, perfumes, pesticides and pharmaceuticals; in the silvering of mirrors; in leather tanning; in the hardening of gelatin fibres; as a denaturant for alcohols; in fuel compositions; in glue and casein products; as a preservative for fish and fruit; as a synthetic flavouring agent; as a food additive; in the paper industry; and as a laboratory chemical.(7,9,11,31,35)
Acetaldehyde is a metabolic intermediate in higher plants and in humans, and occurs naturally in trace quantities in human blood. It is a natural intermediate in the metabolism of ethanol and sugars, and thus occurs in alcoholic beverages, such as wine, beer and spirits. Small amounts are present in ripe fruits, food, fruit juices, several spices, essential oils, roasted coffee, and smoke from cigarettes and marijuana. It is a natural product of combustion and photo-oxidation of non-methane hydrocarbons commonly found in the atmosphere.
It is an important industrial chemical and may be released into the air and wastewater during its production and use. It is also present in vehicle exhaust and from the open burning and incineration of gas, fuel oil, coal and wood.(7,9,11)


Highly volatile, colourless liquid with a penetrating, pungent, suffocating odour that is somewhat fruity and quite pleasant in low concentrations. EXTREMELY FLAMMABLE LIQUID AND VAPOUR. Can form explosive mixtures in air over a wide concentration range. Vapour is heavier than air and can accumulate in low-lying areas or tanks, and may spread long distances. Distant ignition and flash back are possible. The vapours can oxidize in air to form unstable peroxyacetic acid, which is heat sensitive and may explode at high temperatures and high concentrations. Polymerizes rapidly in the presence of trace metals or acids. Closed containers may rupture violently when heated. TOXIC if inhaled. The vapour is irritating to the respiratory tract. May cause lung injury--effects may be delayed. EYE IRRITANT. Causes severe eye irritation. POSSIBLE CANCER HAZARD - may cause cancer, based on animal information.


Effects of Short-Term (Acute) Exposure

Acetaldehyde very rapidly forms extremely high vapour concentrations (almost 100%) at room temperature. Therefore, acetaldehyde must be considered a significant inhalation hazard.
The vapour is detectable by smell at very low concentrations (less than 0.1 ppm). Mild irritation of the upper respiratory tract was noted by 14 volunteers exposed to 134 ppm for 30 minutes.(1) Exposure to greater than 200 ppm for 15 minutes produced mild nose and throat irritation in the majority of 12 volunteers.(2) Higher concentrations (approximately 3000 ppm) are expected to produce intolerable irritation of the nose, throat and upper respiratory passages. The distinct, penetrating, pungent, suffocating odour and irritating properties of acetaldehyde would normally provide adequate warning of a high exposure. However, in extreme situations (e.g. a catastrophic leak), exposure to concentrations high enough to produce potentially fatal lung injury (pulmonary edema) may occur. The signs and symptoms of pulmonary edema, such as coughing and difficulty breathing, can be delayed until hours or days after the exposure. There are no human reports of pulmonary edema, but it has been observed in animal experiments.
Inhalation of aerosolized acetaldehyde for 2 minutes (at 5, 10, 20, and 40 mg/mL) showed a dose-related and marked decrease (greater than 20%) in a lung function test (FEV1) in asthmatics. There was no effect in healthy subjects.(3)

Skin Contact:
Liquid acetaldehyde will quickly evaporate when it comes into contact with the skin. Thus, significant inhalation exposure may occur, with effects as described for "Inhalation" above. Limited animal and human information indicates that brief contact may produce mild irritation. Covered application of 10% acetaldehyde in water to 22 volunteers produced redness and swelling at the site of application.(4)
There is no evidence that acetaldehyde can be absorbed through the skin.

Eye Contact:
Acetaldehyde liquid and vapour causes severe eye irritation, based on limited animal and human information. In humans, corneal burns following direct contact with acetaldehyde showed prompt healing within 48 hours (30/33 cases), slow healing in 3-10 days (3/33) and no cases with loss of vision.(5) There are no further details available. A 15-minute exposure to 50 ppm caused eye irritation in a majority of 12 volunteers. Some individuals experienced irritation at exposures as low as 25 ppm. Exposure to 200 ppm produced bloodshot eyes and reddened eyelids in all volunteers.(2)

Acetaldehyde has relatively low oral toxicity, so large amounts would have to be consumed to produce serious toxicity. Also, acetaldehyde boils near room temperature (20.2 deg C) and will rapidly "boil off" upon contact with human tissue, forming a gas. Thus, with any exposure, significant inhalation exposure is also likely to occur.
If ingestion were to occur, for example with a water solution of acetaldehyde, severe irritation of the mouth, throat and stomach would be expected. Nausea, vomiting, diarrhea and central nervous system (CNS) depression leading to stupor, narcosis and respiratory failure may occur.
Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

Lungs/Respiratory System:
Long-term exposure to low levels of acetaldehyde may result in irritant changes to the surface tissue of the inside of the nose and the upper respiratory system, based on animal information. There is no human information available.

Skin Sensitization:
It is not possible to conclude that acetaldehyde is a skin sensitizer based on the limited animal and human information available.
A case report describes a textile worker with allergic dermatitis on her arms, neck and face. Patch tests were positive for a compound on the treated yarn, as well as to 1.0% acetaldehyde. Negative results were obtained with lower concentrations of acetaldehyde. Previously history of allergies was not discussed.(6)


Acetaldehyde is a possible human carcinogen. Recent human studies have been based on the fact that acetaldehyde is the main metabolite of ethanol, and therefore is present in the bloodstream of people who consume alcoholic beverages. Three studies evaluated the incidence of cancer in relation to people with genetic changes in the enzymes that metabolize alcohol to acetaldehyde. Another study evaluated the link between alcohol intake and breast cancer in women. These studies were reviewed by the International Agency for Research on Cancer (IARC) and were considered to consistently show an increased risk of alcohol-related cancers among genetically predisposed individuals that would lead to higher levels of acetaldehyde in the blood following alcohol intake. A study of chemical plant employees had too many limitations. IARC has concluded that there is inadequate evidence in humans for the carcinogenicity of acetaldehyde. However, there is sufficient evidence for the carcinogenicity of acetaldehyde to experimental animals.(7)

The International Agency for Research on Cancer (IARC) has concluded that this chemical is possibly carcinogenic to humans (Group 2B).

The American Conference of Governmental Industrial Hygienists (ACGIH) has designated this chemical as an animal carcinogen (A3).

The US National Toxicology Program (NTP) has listed this chemical as reasonably anticipated to be a human carcinogen.

Teratogenicity and Embryotoxicity:
No conclusions can be drawn about the possible association between occupational acetaldehyde exposure and the occurrence of developmental effects. There has been considerable discussion of a possible association between acetaldehyde and the developmental effects caused by ingesting large amounts of ethanol (drinking alcohol) - fetal alcohol syndrome. This is because acetaldehyde is formed in the body following ingestion of ethanol. However, the mechanisms by which ethanol causes developmental effects are not completely understood and there are no reports of direct exposure to acetaldehyde causing developmental effects in humans.(9) The available animal studies have not used routes of exposure that are relevant to humans.

Reproductive Toxicity:
There is no human or relevant animal information available.

There is no human information available. It is not possible to conclude that acetaldehyde is mutagenic, based on the available animal information.

Toxicologically Synergistic Materials:
In hamsters, the inhalation of acetaldehyde increased the incidence of respiratory tract tumors produced by benzo(a)pyrene.(10)

Potential for Accumulation:
Acetaldehyde is readily absorbed following inhalation and ingestion. It is distributed in rats to the blood, liver, kidney, spleen, heart, and other muscle tissue. Low levels were detected in rat and mouse embryos after maternal exposure to ethanol. The liver is the most important metabolic site. Acetaldehyde is rapidly metabolized in the liver with a half-life of 15 minutes in the blood stream. The major metabolic pathway is by oxidation to acetate, which is a normal body component. It used up in various metabolic pathways with the eventual production of carbon dioxide and water, or used in the production of chemicals required for bodily functions. Less than 5% of the absorbed acetaldehyde is excreted unchanged in the air and no excretion was found in the urine.(9,11)

Health Comments:
Disulfiram (also called Antabuse), a drug used to treat alcoholism, prevents the metabolism of acetaldehyde.


This chemical is extremely flammable and a possible carcinogen. Take proper precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment, use the buddy system and remove any sources of ignition). Remove source of contamination or move victim to fresh air. If breathing is difficult, trained personnel should administer emergency oxygen. Immediately obtain medical attention.

Skin Contact:
Remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Flush with lukewarm, gently flowing water for 5 minutes. Obtain medical advice. 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 15-20 minutes, while holding the eyelid(s) open. If a contact lens is present, DO NOT delay irrigation or attempt to remove the lens until flushing is done. Immediately obtain medical attention.

NEVER give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. If vomiting occurs naturally, have victim rinse mouth with water again. Immediately obtain medical attention.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some first aid procedures recommended above require advanced first aid training. Protocols for undertaking advanced procedures must be developed in consultation with a doctor and routinely reviewed.
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:
-38 deg C (-36 deg F) (9,31,32,37)

Lower Flammable (Explosive) Limit (LFL/LEL):
4% (32,37); 4.5% (9,31)

Upper Flammable (Explosive) Limit (UFL/UEL):
60% (32,37); 60.5% (9,31)

Autoignition (Ignition) Temperature:
Reported values vary widely; 130-193 deg C (266-379.4 deg F) (9,31,37,38)

Electrical Conductivity:
1.7 X 10(8) pS/m at 15 deg C (39)

Minimum Ignition Energy:
0.37 millijoules (40,41)

Combustion and Thermal Decomposition Products:
Methane and other toxic, irritating chemicals.(31,32,36,37)

Flammable Properties:

Specific Hazards Arising from the Chemical:
Can accumulate in confined spaces, resulting in a toxicity and flammability hazard. Closed containers may rupture violently when exposed to fire or excessive heat for a sufficient period of time.

Extinguishing Media:
Carbon dioxide, dry chemical powder, "multipurpose" alcohol-resistant foam, water fog or spray. Water may be ineffective because it will not cool acetaldehyde below its flash point.(32,37) "Multipurpose " alcohol-resistant foams are recommended for use on flammable liquids, such as acetaldehyde.(37) Foam manufacturers should be consulted for recommendations regarding types of foams and application rates.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid very toxic acetaldehyde vapours and 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. Water can extinguish the fire if used under favourable conditions and when hose streams are applied by experienced firefighters trained in fighting all types of flammable liquid fires.(37)
Closed containers may rupture violently when exposed to the heat of fire and suddenly release large amounts of products. Stay away from ends of tanks, but be aware that flying material (shrapnel) from ruptured tanks may travel in any direction. If possible, isolate materials not yet involved in the fire and move containers from fire area if this can be done without risk. Protect personnel. Otherwise, cool fire-exposed containers, tanks, pipelines or equipment by applying hose streams. Cooling should begin as soon as possible (within several minutes) and should concentrate on any unwetted portions of the container. Apply water from the side and a safe distance. Cooling should continue until well after the fire is out. If this is not possible, use unmanned monitor nozzles and immediately evacuate the area.
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. Water spray can be used to dilute spills to nonflammable mixtures and flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
For an advanced or massive fire in a large area, use unmanned hose holders or monitor nozzles; if this is not possible withdraw from fire area and allow fire to burn. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank.
Tanks, drums or other containers should not be approached directly after they have been involved in a fire or heated by exposure, until they have completely cooled down.

Protection of Fire Fighters:
Acetaldehyde is toxic and a possible human carcinogen. Firefighters may enter the area if positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) and full Bunker Gear is worn.


NFPA - Health: 2 - Intense or continued (but not chronic) exposure could cause temporary incapacitation or possible residual injury.
NFPA - Flammability: 4 - Will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature, or readily disperse in air and burn readily.
NFPA - Instability: 2 - Undergoes violent chemical change at elevated temperatures and pressures, or reacts violently with water, or may form explosive mixtures with water.


Molecular Weight: 44.05

Conversion Factor:
1 ppm = 1.80 mg/m3; 1 mg/m3 = 0.556 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: -123.5 deg C (-190.3 deg F) (9,31,38,39)
Boiling Point: 20.2 deg C (68.3 deg F) (31,38)
Relative Density (Specific Gravity): 0.785 at 15 deg C (31); 0.778 at 20 deg C (9,31) (water = 1)
Solubility in Water: Soluble in all proportions.(9,31,38,39)
Solubility in Other Liquids: Soluble in all proportions in most common organic solvents including ethanol, acetone, diethyl ether, benzene, gasoline, toluene, xylenes, turpentine, solvent naphtha and acetic acid.(31,35)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = -0.34 (measured) (35,46); -0.22 to -0.17 (estimated) (46)
pH Value: Not available
Acidity: Very weak acid; pKa = 14.16 (Ka = 0.7 X 10(-14)) at 0 deg C (9,31,38); 13.57 at 25 deg C (35,50)
Viscosity-Dynamic: 0.246 mPa.s (0.246 centipoise) at 15 deg C (31,35); 0.21-0.22 mPa.s (0.21-0.22 centipoise) at 20 deg C (38)
Viscosity-Kinematic: 0.313 mm2/s (0.313 centistokes) at 15 deg C; 0.27-0.28 mm2/m (0.27-0.28 centistokes) at 20 deg C (calculated)
Saybolt Universal Viscosity: 26.4 Saybolt Universal Seconds at 37.8 deg C (100 deg F) (calculated)
Surface Tension: 21.2 mN/m (21.2 dynes/cm) at 20 deg C (31,38)
Vapour Density: 1.52 (air = 1) (calculated)
Vapour Pressure: 80 kPa (620 mm Hg) at 15 deg C (31); 100 kPa (760 mm Hg) at 20 deg C (31)
Vapour Pressure at 50 deg C: 281.5 kPa (2.78 atm) (calculated) (39)
Saturation Vapour Concentration: Extremely high; gas at room temperature.
Evaporation Rate: Not available. Acetaldehyde is highly volatile.
Henry's Law Constant: 8.0 Pa.m3/mol (cited as 3.23 x 10(-3) (dimensionless)) at 25 deg C (experimental) (55); 3.16 Pa.m3/mol (cited as 1.32 x 10(-3) (dimensionless)) at 15 deg C (estimated) (56)
Critical Temperature: 181.5 deg C (358.7 deg F; 454.7 deg K) (31,38); 188 deg C (730 deg F; 461 deg K) (39,49)
Critical Pressure: 5550 kPa (54.77 atm) (estimated) (49); 6400 kPa (63.15 atm) (31)

Other Physical Properties:
DIELECTRIC CONSTANT: 21.1 at 21 deg C (39)


Pure acetaldehyde is stable in the absence of air and sunlight (UV light).(9,31) Acetaldehyde oxidizes in air to form acetic acid and unstable peroxyacetic acid, which is sensitive to heat and is explosive at high temperatures (100 deg C) and high (but not low) concentrations.(42)

Hazardous Polymerization:
Pure acetaldehyde does not polymerize spontaneously. It polymerizes rapidly in the presence of trace metals (e.g. iron) or acids.(42)

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.

OXYGEN (including oxygen in air) - reacts exothermically (generation of heat) to form peroxyacetic acid and acetic acid. Peroxyacetic acid may decompose violently at high concentrations and temperatures greater than 100 deg C.(42)
ACIDS (e.g. concentrated sulfuric acid or acetic acid) or ALKALIES (e.g. sodium hydroxide) - trace amounts in acetaldehyde cause rapid polymerization, which produces a great amount of heat and can lead to violent explosion and fire.(32,37,42)
METALS (e.g. iron, aluminum or copper and their alloys) - trace amounts of metal cause rapid polymerization, which produces a great amount of heat and can lead to violent explosion and fire.(42)
OXIDIZING MATERIALS (e.g. fluorine, nitric acid, nitrates, peroxides or perchlorates) - acetaldehyde is a strong reducing agent which reacts violently with oxidizing agents. Increased risk of fire and explosion.(37,40)
HYDROGEN PEROXIDE and WATER (ratio of hydrogen peroxide to water is greater than 1) - mixtures may be explosive. If the overall fuel-peroxide composition is stoichiometric, the explosive power and sensitivity may be equivalent to those of glyceryl nitrate.(42)
SILVER NITRATE - aqueous silver nitrate reacts with acetaldehyde to form explosive silver fulminate.(42)
MERCURY(II) OXOSALTS (e.g. mercury(II) chlorate or mercury(II) perchlorate) - some of the products of interaction with acetaldehyde are highly explosive and extremely shock-sensitive.(42)

Hazardous Decomposition Products:
Acetic acid, peroxyacetic acid

Conditions to Avoid:
Heat, hot surfaces, sparks, static discharge, open flames, other ignition sources, air, sunlight, contamination.

Corrosivity to Metals:
Dry, pure acetaldehyde is not corrosive to metals, such as aluminum, carbon steel, Hastelloy, stainless steels (types 304/347, 316 400 series, 20 Cb 3), Monel, nickel, tantalum, titanium and zirconium.(51,52) In air, acetaldehyde can be oxidized to acetic acid, which is corrosive to some metals, such as carbon steel, copper and its alloys (brass and bronze) and aluminum at high temperatures.(51,52) Acetaldehyde vapour leaking into a building equipped only with flameproof electrical equipment ignited, possibly on contact with rusted steel, corroded aluminum or hot steam lines.(42)

Corrosivity to Non-Metals:
Acetaldehyde attacks some plastics, such as Acrylonitrile-butadiene-styrene (ABS), acrylics, CPVC, nylon, polyesters, high molecular weight polyethylene, polystyrene and PVC, elastomers, such as Viton A, isoprene, natural rubber, nitrile Buna-N and polyurethane, and coatings, such as epoxy, polyester and vinyls.(51,53)


LC50 (rat): 8722 ppm (4-hour exposure); cited as 15.7 g/m3 (4-hour exposure) (12)

LD50 (oral, rat): 660 mg/kg (13)

Eye Irritation:

Limited information suggests acetaldehyde is a severe irritant.

An unconfirmed report describes severe irritation in rabbits following application of 40 mg acetaldehyde.(11,14)

Skin Irritation:

Limited information suggests acetaldehyde is a mild irritant.

No irritation was observed in guinea pigs after covered application of 10% acetaldehyde in saline.(15) An unconfirmed report describes mild irritation in rabbits following uncovered application of 500 mg.(11,14)

Effects of Short-Term (Acute) Exposure:

Acetaldehyde causes irritant injury to the respiratory system following inhalation and to the stomach following ingestion. Inhalation for 4-5 weeks has produced intense irritation in the upper respiratory tract and lung injury. Lethal oral doses have caused respiratory distress and paralysis.

Rats exposed for 1-minute intervals to 278 or 556 ppm showed no effects on blood pressure or heart rate. At 1668-16680 ppm, there were dose-related increases in blood pressure. At 6672 and 13900 ppm, there were also increases in heart rate.(16) The 10-minute RD50, the concentration which produces a 50% reduction in the respiratory rate, is 2991 ppm for rats and 2845 ppm for mice.(17,18) Exposure to this concentration is expected to produce intolerable eye, nose and throat irritation (sensory irritation) in humans. Rats exposed for 5 weeks to 243 ppm showed an increase in various measurements of lung function, lung damage lung and intense irritation in the nasal cavities.(19) In another study, rats exposed for 4 weeks to 110, 150 or 500 ppm showed changes in the tissue lining the nose at 500 ppm only.(20) Rats exposed for 4 weeks to 0, 400, 1000, 2200 or 5000 ppm showed dose-related injury to the surface tissue of upper respiratory tract (the nose, larynx and trachea). At 5000 ppm, shortness of breath and excitation were observed during exposure. Increased lung weight was also noted.(21)

In an oral LD50 study, respiratory distress, gasping and paralysis was observed. Surviving animals recovered quickly from exposure but there was a delayed effect producing respiratory distress, stupor and death within 24 hours.(13) Rats given 0, 25, 125 or 675 mg/kg/day in drinking water for 4 weeks showed slight to moderate thickening of the forestomach at the highest dose, as well as reduced food and water consumption. There were no other treatment related effects.(22)

Effects of Long-Term (Chronic) Exposure:

Inhalation of 750 ppm and above has produced dose-related reduced growth and irritant changes to the surface tissue of the nose in rats and hamsters. Bronchopneumonia and sinus inflammation, as well as changes in the larynx and trachea were also noted. Recovery of nasal tissue occurred with lower exposures but not with highest exposures. Oral studies have shown that acetaldehyde caused changes in the liver, as well as irritant changes in the lining of the upper gastrointestinal tract.

Rats were exposed to 0, 750, 1500 or 3000/1000 ppm for 2 years. A sub-group was exposed for 1 year, followed by a 26 or 52 week recovery period. Dose-related reduced growth and changes in the surface tissue of the nose were observed. The highest concentration was reduced to 1000 ppm during the first year due to severely reduced growth and high mortality. This group also showed bronchopneumonia and sinusitis.(23) Follow-up for 1 year showed that the cell changes progressed to cancer in surviving animals. No recovery to the nasal epithelium was observed in animals exposed to the highest concentration. At lower concentrations, recovery was not evident at 26 weeks, but was at 52 weeks.(24) Hamsters exposed 0, 390, 1340 or 4560 ppm for 90 days showed damage to the upper respiratory tract and reduced growth. At 4560 ppm, reduced growth and severe respiratory tract changes, including effects on the larynx and trachea, were observed. There was also eye and nose irritation. At 1340 ppm, the effects were less severe. At 390 ppm, no toxic effects were observed.(25) Hamsters were exposed to 2500/1650 ppm for 52 weeks. Marked changes to the nose, larynx and trachea were observed. During a 6-month recovery period, the effects persisted. There were no changes in the bronchi or lungs. The exposure concentration was gradually reduced due to severe growth reduction and to avoid early mortality.(10)

Oral studies have explored the role of acetaldehyde (as a metabolite of ethanol) in relation to injury caused by ethanol ingestion. Acetaldehyde has caused an increase in total collagen content of the liver following ingestion in drinking water.(26) Dosing directly into the stomach or colon has shown that it can cause focal change and inflammation in the liver.(27) Doses of 324 mg/kg/day in drinking water for 8 months caused irritant changes in the lining of the upper gastrointestinal tract in rats.(28)

Skin Sensitization:
Positive results were reported in a non-standard test, where relatively high relatively high concentrations of acetaldehyde were used.
Dose-related sensitization was observed in 4-5/15, 7-9/15 and 13/15 guinea pigs exposed to 2.5, 5.0 and 10.0%, respectively at 48 and 72 hours after induction with 15% acetaldehyde in saline (modified cumulative contact enhancement test (CCET), with an adjuvant). Re-challenge 78 days after induction showed no response with 0.03 or 2.5% acetaldehyde.(15)

The International Agency for Research on Cancer (IARC) has concluded that there is sufficient evidence in experimental animals for the carcinogenicity of acetaldehyde.(7)
A two-year study with rats exposed to 0, 750, 1500 or 3000 ppm showed a concentration-related increased incidence of nasal carcinomas. Due to toxicity, the highest concentration was progressively reduced to 1000 ppm. Respiratory tract tissue damage was observed at all concentrations.(23) In another study, hamsters exposed to 2500/1650 ppm for 52 weeks showed nasal and laryngeal tumors. However, only the incidence of laryngeal tumors was statistically significant. The exposure concentration was gradually reduced due to severely reduced growth and to avoid early mortality.(10)

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
Several studies have investigated the role of acetaldehyde in ethanol-induced teratogenicity. While some do report teratogenic, embryotoxic or fetotoxic effects, these results are not considered relevant since the routes of exposure (intravenous, intraperitoneal or intraamniotic) do not represent possible routes of human exposure nor was maternal toxicity adequately evaluated.(9,29)

Reproductive Toxicity:
No reports were located that used routes of exposure that are relevant to humans.

There is insufficient information to conclude that acetaldehyde is mutagenic.
Rats receiving single 6-hour exposures (0, 100, 300, 1000 or 3000 ppm) showed dose-related DNA damage (DNA protein crosslinks) in the nasal mucosa. Results were only statistically significant at 1000 ppm and above; concentrations which are also toxic to the cells.(30) Other studies using live animals have used exposure routes that do not represent possible routes of human exposure, thus are not relevant for evaluation.
There have been many reports of positive in vitro cultured mammalian cell studies using a variety of test systems and cell types. Bacteria tests have had both positive and negative results.(7)
Positive and negative results have been obtained in fruit flies.(7)


Selected Bibliography:
(1) Sim, V.M., et al. Effect of possible smog irritants on human subjects. Journal of the American Medical Association. Vol. 165, no.15 (Dec. 14, 1957). p. 1908-1913
(2) Silverman, L., et al. Further studies on sensory response to certain industrial solvent vapors. Journal of Industrial Hygiene and Toxicology. Vol. 28, no. 6 (Nov. 1946). p. 262-266
(3) Myou, S., et al. Aerosolized acetaldehyde induces histamine-mediated bronchoconstriction in asthmatics. American Review of Respiratory Disease. Vol. 148, no. 4 (1993). p. 940-943
(4) Haddock, N.F., et al. Cutaneous reactions to lower aliphatic alcohols before and during Disulfiram therapy. Archives of Dermatology. Vol. 118 (Mar. 1982). p. 157- 159
(5) McLaughlin, R.S. Chemical burns of the human cornea. American Journal of Ophthalmology. Vol. 29, no. 11 (Nov. 1946). p. 1355-1362
(6) Shmunes, E., et al. Allergic contact dermatitis to dimethoxane in a spin finish. Contact Dermatitis. Vol. 6, no. 6 (1980). p. 421-424
(7) International Agency for Research on Cancer (IARC). Acetaldehyde. In: IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 71, parts 1, 2 and 3. Re-evaluation of some organic chemicals, hydrazine and hydrogen peroxide. World Health Organization, 1999
(8) Report on Carcinogens. 11th ed. US Department of Health and Human Services, Public Health Service, National Toxicology Program
(9) International Programme on Chemical Safety (IPCS). Acetaldehyde. Environmental Health Criteria; 167. World Health Organization, 1995
(10) Feron, V.J., et al. Respiratory tract tumors in hamsters exposed to acetaldehyde vapour alone or simultaneously to benzo(a)pyrene or diethylnitrosamine. European Journal of Cancer and Clinical Oncology. Vol. 18, no. 1 (1982). p. 13-31
(11) Acetaldehyde. In: Documentation of the threshold limit values and biological exposure indices, supplement. American Conference of Governmental Industrial Hygienists, 1996
(12) Safronov, G.A., et al. Comparative acute inhalation toxicity of aliphatic aldehydes and ketones according to exposure time. Current Toxicology. Vol. 1, no. 1 (1993). p. 47-51
(13) Sprince, H., et al. Protection against acetaldehyde toxicity in the rat by L-cysteine, thiamin and L-2- methylthiazolidine-4-carboxylic acid. Agents and Actions. Vol. 4, no. 2 (1974). p. 125-130
(14) National Institute for Occupational Safety and Health (NIOSH). Acetaldehyde. Last updated: 1999-07. Registry of Toxic Effects of Chemical Substances (RTECS(R)). [CD-ROM]. Canadian Centre for Occupational Health and Safety (CCOHS). Also available at: <> {Subscription required}
(15) Bergh, M., et al. Sensitizing potential of acetaldehyde and formaldehyde using a modified cumulative contact enhancement test (CCET). Contact Dermatitis. Vol. 40 (1999). p. 139-145
(16) Egle, J.L., Jr. Effects of inhaled acetaldehyde and propionaldehyde on blood pressure and heart rate. Toxicology and Applied Pharmacology. Vol. 23, no. 1 (1972). p. 131-135
(17) Babiuk, C., et al. Sensory irritation response to inhaled aldehydes after formaldehyde pretreatment. Toxicology and Applied Pharmacology. Vol. 79, no. 1 (June 15, 1985). p. 143-149
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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: 2003-03-19

Revision Indicators:
PEL transitional comments 2004-02-02
Resistance of materials for PPE 2004-04-08
Vapour pressure at 50 deg C 2005-09-26
Bibliography 2006-01-03
WHMIS detailed classification 2006-01-19
WHMIS proposed classification 2006-01-19
WHMIS health effects 2006-01-19
Emergency overview 2006-01-19
Handling 2006-01-24

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