Table 2-1 Physical and Chemical Properties of Acetaldehyde


Acetic aldehyde, ethanal, ethyl aldehyde

CAS registry number


Molecular formula


Molecular weight


Boiling point


Melting point


Flash point

−38.9°C (closed cup)

Explosive limits

Lower limit, 4.1%; upper limit, 55% by volume

Specific gravity

0.788 at 16°C

Vapor pressure

902 mmHg at 25°C


Miscible with water and most common organic solvents

Conversion factors

1 ppm = 1.8 mg/m3; 1 mg/m3 = 0.56 ppm

Sources: Budavari et al. 1989, HSDB 2005.

anaerobic metabolism of glucose by intestinal microflora (NRC 1994). Acetaldehyde is eliminated in expired air of fasted humans at 17 μg/h (NRC 1994).

Acetaldehyde is a component of tobacco smoke. The amount of acetaldehyde generated depends on the type of cigarette. Results of several studies indicate a range in the amount of acetaldehyde in the smoke of 400-1,400 μg/cigarette (IARC 1985; Hoffmann and Hecht 1990), although results of one study indicate a much lower emission of acetaldehyde from low-tar cigarettes (90-270 μg/cigarette; IARC 1985). Acetaldehyde is also a component of automobile exhaust and is generated by the combustion of wood and plastics (IARC 1985). Several studies have measured acetaldehyde concentrations in ambient air in the United States; results range from nondetectable to 69 ppb (IARC 1985).

Acetaldehyde concentrations have been measured on nuclear-powered submarines. Raymer et al. (1994) reported the results of air sampling at three locations over 6 h during the missions of two submarines. Acetaldehyde concentrations ranged from 78 to 130 ppb on an attack submarine and from 210 to 250 ppb on a ballistic-missile submarine. Holdren et al. (1995) reported the results of a similar sampling exercise (two submarines, three locations, and sampling duration of 6 h). Concentrations ranged from 46.6 to 97.2 ppb on a nuclear-powered attack submarine and from 103.9 to 118.0 ppb on a ballistic-missile submarine. Hagar (2008) reported data representing 228,960 h (318 patrols) on 23 attack submarines and 77,760 hours (108 patrols) on 10 ballistic-missile submarines. Acetaldehyde concentrations were determined with passive monitoring and averaged 16 ppb (range, 1-110 ppb) on the attack submarines and 5 ppb (range,

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