The determination of acetaldehyde in exhaled breath.

Breath acetaldehyde has been used to investigate the production of acetaldehyde after ethanol ingestion in ALDH2-deficient individuals, to compare ethanol and acetaldehyde metabolism, to study the toxicological outcome of metabolic inhibitors of ALDH2, and as a biomarker of exposure to ethanol vapours. A number of approaches have been developed to collect representative breath samples (mixed air or alveolar air) and to measure breath acetaldehyde. For instance, the highest breath concentration of acetaldehyde (approximately 50 nmoles/1) measured during pulmonary ethanol exposure (1000ppm, 6 hours) is of the same magnitude as those measured after ingestion of 0.4-0.8 g/kg (-60-80 nmoles/ i), whereas endogenous levels rarely exceed 1 nmole/l. The interpretation of breath acetaldehyde is compounded by several factors; smoking, ALDH2 polymorphism and alcohol drinking habits are associated with higher breath/blood levels. Some authors have considered that breath acetaldehyde, particularly low levels, cannot be used to estimate blood acetaldehyde. Despite the problems associated with its determination, breath acetaldehyde could be an interesting tool for estimating ethanol or acetaldehyde exposure. However, some additional research efforts will be necessary in order to standardize the technique used for breath sampling and to control the influence of the factors that are known to affect breath acetaldehyde determination.