Measurement of acetaldehyde: what levels occur naturally and in response to alcohol?

The aim of the present paper is to update the status regarding human acetaldehyde levels in blood, breath and saliva during normal ethanol oxidation, i.e. without deficiency in, or inhibition of, aldehyde dehydrogenase activity. The previous conclusion according to which no detectable (<0.5 microM), adequately determined 'free and/or loosely bound' acetaldehyde has not yet been found in venous blood, more or less, still holds. The only new findings within this context consist of low venous blood acetaldehyde levels (1-3 microM on average) observed in some women during the use of oral contraceptives or during the high oestradiol phases of normal menstrual cycle. Breath acetaldehyde levels are about 10-20 and 20-40nM at blood ethanol concentrations of about 10 and 20mM, respectively. Theoretically calculated corresponding blood acetaldehyde levels in pulmonary blood would be about 2-4 and 4-8 microM. The acetaldehyde in the breath most likely reflects pulmonary blood acetaldehyde, microbial and tissue acetaldehyde production in the aerodigestive tract. As well as with breath acetaldehyde, salivary acetaldehyde levels also correlate positively with the blood ethanol concentrations. At blood ethanol concentrations of about 10 and 20 mM the average acetaldehyde concentration in saliva is about 15-25 and 20-40 microM, respectively. Saliva acetaldehyde represents mostly microbial acetaldehyde formation in the oral cavity, but also, to some extent, ethanol oxidation in nearby tissues. More studies are still needed to clarify the proportion of the underlying sources for blood, breath and salivary acetaldehyde at different ethanol concentrations. The problem with rapid acetaldehyde oxidation, which may markedly affect the recovery of low acetaldehyde levels, also needs to be solved.