I have mentioned in numerous posts that a primary problem with blood alcohol analysis is that the no two individuals are alike in their physiology and metabolism of alcohol (see, for example, "Convicting the Average Person", "Racial Differences in the Metabolism of Alcohol" and "High Blood Alcohol — or a Zinc Deficiency?"). Further, many external factors can influence attempts to measure blood alcohol levels (see, for example, "Under the Influence of….Gasoline?", "Asthma Inhalers Can Cause High Breathalyzer Results" and "Driving Under the Influence of….Paint?").
One of many other factors that render attempts to estimate an individual’s blood alcohol concentration at a given point in time is smoking. A scientific study has found that cigarette smoking can influence absorption by the body of alcohol — and thus, among other things, attempts to estimate earlier blood alcohol levels when driving based upon tested levels. Johnson et al., "Cigarette Smoking and Rate of Gastric Emptying: Effect on Alcohol Absorption", 302 British Medical Journal 20 (1991).
The researchers reported testing blood samples of a group of smokers for blood alcohol levels both after smoking and after prolonged abstinence. The result was that "areas under the venous blood alcohol concentration-time curves between zero and 30 minutes and 60 minutes and the peak blood alcohol concentrations were significantly less during the smoking period compared with the non-smoking period". Gastric emptying was also found to be slower during the smoking evaluation.
The scientists concluded that the effect of smoking on alcohol absorption has "considerable social and medicolegal relevance", and that the ingestion of nicotine should be taken into when dealing with alcohol metabolism.