An Unusual Toxicological Property of Alcohol: The Density Effect on the Organ of Balance,

Some airlines require that their pilots observe 24 hours of abstinence from alcohol before flying, and some require only 12 hours of abstinence. Some civilian 12 and some military organizations require only eight hours of abstinence before flying, and it has even been suggested 10 that no fixed period of abstinence need be required as long as the blood alcohol concentration is 20 mg per 100 ml or lower when flying starts. Confidence in the supposedly-innocuous influence of blood alcohol levels below 20 mg per 100 ml is apparently based on the inability to measure alcohol-induced performance decrements at blood alcohol levels below 20 1,10, or below 45 during the decreasing phase of the blood concentration 18. Aside from the narrow validity of negative evidence, and aside from the possibility that important, although unmeasured, performance decrements occur with lower concentrations of blood alcohol, it has been shown that the effects of alochol on the vestibular system can be hazardous to flight safety while boold concentrations are falling below 40, below 20, and even for several hours after the blood concentration reaches zero 3,4,15,28,30. This effect of alcohol is revealed by positional alcohol nystagmus phase II PAN II.