INDUSTRIAL CHEMICALS – POSSIBLE CARCINOGEN (IARC 2B)
Acetaldehyde is a colourless and volatile liquid with a sharp and fruity odour. It is widely used industrially as a chemical intermediate. Acetaldehyde is also a metabolite of sugars and ethanol in humans, is found naturally in the environment, and is a product of biomass combustion. It may also be referred to as ethanal or acetic aldehyde. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
Acetaldehyde has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans, based on evidence in animals. Acetaldehyde is a respiratory tract carcinogen in experimental animals, especially of the nasal mucosa in rats and of the larynx in hamsters.
There is inadequate evidence for the carcinogenicity of acetaldehyde in humans. One small study of workers manufacturing several types of aldehydes found increased risk of bronchial tumours, but workers were exposed to many other chemicals in addition to acetaldehyde. Three other studies on the carcinogenicity of alcoholic beverages found that people who developed cancer after heavy alcohol use had genetic differences and higher concentrations of acetaldehyde in their blood compared to those who didn’t develop cancer. Further study is required to establish a causal relationship.
Regulations and Guidelines
|Canadian Jurisdictions||OEL (ppm)|
|Canada Labour Code||25 [c]|
|BC, AB, SK, MB, NU, ON, QC, NL, PE, NS, NT||25 [c]|
|Other Jurisdiction||OEL (ppm)|
|ACGIH 2020 TLV||25 [c]|
ppm = parts per million
c = ceiling (not to be exceeded at any time)
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines and standards*
|Canada’s Residential Indoor Air Quality Guidelines||24 hours: 280 µg/m3
1 hour: 1,420 µg/m3
|Ontario Ambient Air Quality Criteria||24 hour: 500 μg/m3
1/2 hour: 500 μg/m3
|Ontario’s Air Pollution – Local Air Quality Regulation Standards||Half-hour standard: 500 µg/m3
24 hour standard: 500 µg/m3; Prohibited discharge into the air if the concentration of acetaldehyde exceeds the standard
|Alberta Ambient Air Quality Criteria||1 hour: 90 μg/m3||2017|
|BC’s Contaminated Sites Regulation, BC Reg 375/96||Sets vapour standards for the protection of human health:
Agricultural, urban park, residential uste standard: 4.5 μg/m3
Commercial use standard: 15 μg/m3
Industrial use standard: 40 μg/m3
Parkade use standard: 35 μg/m3
(Vapours derived from soil, sediment, or water)
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
ppm = parts per million
|Health Canada||DSL – low priority substance (already risk managed)||2006|
|CEPA||Schedule 1, paragraphs ‘b’ and ‘c’||1999|
|National Classification System for Contaminated Sites||Rank = “High hazard”, potential human carcinogen||2008|
|Environment Canada’s National Pollutant Release Inventory||Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than 10 tonnes||2016|
|PMRA List of Formulants||List 3: formulants that do not meet the criteria of any of the other lists||2017|
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
Acetaldehyde was not included in other Canadian government guidelines, standards, or chemical listings reviewed.
Acetaldehyde is used primarily as a chemical intermediate, especially in producing acetic acid, pyridine, and butylene glycol.
Acetaldehyde is also used as a food additive for flavouring. In the US, it falls under the Food and Drug Administration’s definition of “generally recognized as safe” (GRAS), although some researchers have been calling for a re-evaluation of this classification. Acetaldehyde is also used to produce some fragrances and flavours, pesticides, dyes, synthetic rubber, disinfectants, lacquers and varnishes, photographic chemicals, and room air deodorizers. Acetaldehyde has also been used in hydraulic fracturing fluids.
Canadian Production and Trade
The United States is the primary supplier of acetaldehyde to Canada and the second largest exporter in the world next to China.
Production and trade
In the environment, inhalation is the most important route of exposures to acetaldehyde. A significant source of inhalation exposure to the general population is biomass combustion, which is typically higher in urban areas (from vehicles, industrial burning, forest fires, and cigarette smoke).[1,3] CAREX Canada estimates that the acetaldehyde levels in outdoor air do not result in higher risk of cancer at a population level (low data quality). However, results show that acetaldehyde levels in indoor air do result in an increased risk of cancer (moderate data quality).
Canadian studies in Prince Edward Island and Saskatchewan measured indoor air concentrations of several compounds, including acetaldehyde, and found that smoking was a significant source of acetaldehyde in homes. This was the case especially when air exchange rates were lower.[33,34] Cooking with oil was also associated with increased levels of acetaldehyde indoors.
Acetaldehyde, along with several other volatile organic compounds, is released from common building materials such as engineered wood products typically used in manufactured homes. This creates potential for exposure to inhabitants of these homes.
A review of acetaldehyde toxicity from the Government of California published in 2008 lists several studies from the last 15-20 years where measurements of acetaldehyde were taken in residences as well as portable classrooms. According to this review, indoor measurements of acetaldehyde usually greatly exceed outdoor measurements.
Acetaldehyde is a metabolic intermediate in humans and other organisms. It is also found naturally in some foods in trace amounts, especially after cooking, ripening of fruit, or fermentation (i.e. in beer and wine). The largest source of exposure to acetaldehyde in the general population is technically via alcohol consumption, where it is produced during alcohol metabolism. However, acetaldehyde is not carcinogenic via ingestion.
Searches of Environment Canada’s National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to acetaldehyde in Canada:
NPRI and US Household Products Database
|Substance name: ‘Acetaldehyde’|
|Released into Environment||668 t||Pulp, paper and paperboard mills,
veneer, plywood manufacture,
|Disposed of||0.024 t|
|Sent to off-site recycling||None|
|US Household Products 2016|
|Results: 13 products|
|Search Term||Quantity||Product Type|
|‘Acetaldehyde’||13||Arts & crafts adhesives (5), home adhesives (5),
landscape adhesive(1); powdered roof leveler (1);
automotive products (1)
t = tonne
For more information, see the environmental exposure estimate for acetaldehyde.
Occupational Exposures Overview
Inhalation is the most important route of occupational exposure. CAREX Canada estimates that approximately 6,400 Canadians are exposed to acetaldehyde in the workplace. The largest industrial groups exposed are plastic products manufacturing, farms, and bakeries and tortilla manufacturing. By occupation, the greatest exposures occur among labourers in food and beverage processing, managers in agriculture, and process control and machine operators in food and beverage processing.
In food manufacturing, workers are exposed to acetaldehyde during diacetyl production. Diacetyl is a substance used for food flavouring, especially in microwave popcorn. Recent studies from the Netherlands and the US have measured acetaldehyde exposure during production of diacetyl.
Because acetaldehyde is also a combustion product, exposure in the petroleum, transportation, waste burning, fire fighting, and wood products industries is also possible.
For more information, see the occupational exposure estimate for acetaldehyde.
- International Programme for Chemical Safety (IPCS) INCHEM. WHO 1995: Acetaldehyde
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