Is Acetaldehyde safe when breathed in?

Acetaldehyde is classified as possibly carcinogenic to humans (IARC Group 2B) and a probable human carcinogen (U.S. EPA Class B2) based on sufficient evidence of respiratory tract tumors in animals following inhalation exposure.

Why here

Inhalation exposure to acetaldehyde has consistently shown to cause tumors in the respiratory tract of experimental animals.

What would have to be true

Chronic inhalation exposure at concentrations that induce tissue damage in the respiratory tract, such as those leading to nasal adenocarcinomas and squamous cell carcinomas in rats, and laryngeal and nasal carcinomas in hamsters.

The other side

N/A.

Inhalation of acetaldehyde can cause irritation to the eyes, nose, throat, and upper respiratory tract in humans, leading to symptoms such as coughing, breathing difficulties, and at higher concentrations, pulmonary edema.

Why here

Direct contact of inhaled acetaldehyde vapor with mucous membranes of the respiratory system and eyes.

What would have to be true

Short exposures to concentrations exceeding approximately 90 mg/m³ for eye irritation and 240 mg/m³ for upper respiratory tract irritation in humans. Nose and throat irritation reported at 50–200 ppm (89–357 mg/m³). Higher levels can lead to pulmonary edema.

The other side

N/A.

Inhaled acetaldehyde can directly cause bronchoconstriction in people with asthma and potentiate bronchoconstriction responses to other challenges at concentrations as low as 22 mg/m³.

Why here

Acetaldehyde directly interacts with human airways, leading to constriction and inflammation, particularly in susceptible individuals.

What would have to be true

Acute inhalation exposure at concentrations as low as 22 mg/m³ for potentiating bronchoconstriction, and 350–1,000 mg/m³ for direct bronchoconstriction in asthmatics.

The other side

N/A.

Acetaldehyde, as a metabolite of alcohol, can induce airway mast cells to release histamine, which may exacerbate asthma in susceptible populations.

Why here

Acetaldehyde, whether inhaled or produced metabolically, can trigger physiological responses in the airways.

What would have to be true

Elevation of acetaldehyde levels in the body, such as following alcohol consumption, in susceptible individuals.

The other side

While the mechanism is described, the direct causation and prevalence of this effect from environmental inhalation (not alcohol metabolism) in the general population might require further large-scale human studies.

Acetaldehyde is classified as a probable or suspected human carcinogen based on sufficient evidence from animal inhalation studies showing tumors in the respiratory tract.

Why here

Acetaldehyde is a common indoor air pollutant emitted from various sources like combustion, building materials, and consumer products, leading to chronic inhalation exposure.

What would have to be true

Chronic inhalation exposure to levels found in indoor air, with some studies showing concentrations in homes exceeding reference concentrations (e.g., 82% of new California homes exceeding US EPA's 9 µg/m³ reference concentration for chronic inhalation exposure). Animal studies observed effects at higher concentrations, such as nasal tumors in rats and laryngeal tumors in hamsters following inhalation exposure.

Acetaldehyde in indoor air can cause irritation to the eyes, skin, and upper and lower respiratory tract, and can induce bronchoconstriction in asthmatics.

Why here

Acetaldehyde is a volatile compound present in indoor air from various sources, and its irritating properties are observed upon inhalation.

What would have to be true

Acute exposure to concentrations as low as 22 mg/m³ can induce eye irritation and potentiate bronchoconstriction in asthmatics. Nose and throat irritation are reported at 50–200 ppm (89–357 mg/m³). Long-term exposure can lead to tissue damage in the upper respiratory tract.