INVITED REVIEW MEASURING AND REPORTING THE CONCENTRATION OF ACETALDEHYDE IN HUMAN

Abstract—Most of the acetaldehyde generated during the metabolism of ethanol becomes tightly bound to endogenous molecules such as haemoglobin, amino acids and certain phospholipids. Free acetaldehyde passes the blood-brain barrier and traces of this toxic metabolite are excreted through the lungs and can be detected in the expired air. The blood/air partition coefficient of acetaldehyde at 34 °C, the average temperature of end-expired air, is about 190:1. Because of various problems associated with measuring acetaldehyde in blood samples, several research groups have instead investigated the analysis of acetaldehyde in breath which offers an indirect and alternative approach for clinical and research purposes. However, care is needed when interpreting the results of breath acetaldehyde measurements, because of the possibility of local formation from microflora inhabiting the upper airways and mouth. The concentration of acetaldehyde exhaled in breath after drinking alcohol demonstrates large inter-individual differences depending on various genetic (racial) and environmental factors. Moreover, acetaldehyde is an endogenous metabolite and even without drinking any alcohol the concentrations expelled in breath span from 0.2 to 0.6nmol/l, with higher levels observed in smokers and abstinent alcoholics. Breath acetaldehyde concentration reached between 5 and 50nmol/l in European subjects who drank a moderate dose of ethanol (0.4-0.8 g/kg), with the highest values seen in smokers. The concentration of breath acetaldehyde in Japanese subjects after drinking alcohol reached betwee