Regulation
The metabolic chain for ethanol is as follows: Ethanol Acetaldehyde Acetaldehyde Dehydrogenase (isoenzymes, polymorphisms) Acetal Co-enzyme A Intermediary Metabolism
to individuals who consume alcohol. These individuals, whose epithelium is bathed in sweat (which according to the authors would contain more than enough ethanol to fuel the production of acetaldehyde in these bacteria), would have a significant amount of acetaldehyde present on the surface of their skin for hours after imbibing alcoholic beverages. This information is not necessarily earth shattering news, but is certainly food for thought. After an in-depth investigation of the facts surrounding the dermal toxicity and carcinogenicity of acetaldehyde, one glaring deficiency has been identified: Where
are studies that quantify how much acetaldehyde actually binds to skin after application of ethanol or acetaldehyde? It has been reported that hand sanitizer only remains on the skin for a matter of seconds before it evaporates. The boiling point (BP) of ethanol is 173 degrees Fahrenheit at 760 millimeters of mercury (mm/hg), which is the major portion of hand sanitizer. The BP of acetaldehyde is 70 degrees at 760 mm/hg. With a human skin surface temperature that is 28.6 degrees higher than the BP of acetaldehyde, the question of how much of that volatile compound actually makes its way to epithelium seems to be the $100,000 ques-
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Acetate Co-enzyme A
tion. Unfortunately, it does not appear that anyone has done that study yet. But it is not a stretch of the imagination to say that if hand sanitizer only remains on the skin for a matter of seconds (not minutes), and acetaldehyde is at least 2.5 times more volatile than ethanol, the amount of acetaldehyde making its way to bare epithelium is going to be miniscule. This, coupled with the extremely low amounts of acetaldehyde present in ethanol, paints a sobering (excuse the pun) picture of how much of this compound actually contacts and remains on the skin. In the absence of real data concerning the migration of acetaldehyde to skin via hand sanitizer formulations, it would be wise to ponder the fact that every toxicologist knows: The dose makes the poison.
In Our Food
The FDA is very likely to rescind, in the near future, the temporary rules that allow for higher levels of acetaldehyde. The result will be a reduction in the availability of ethanol used to make sanitizers to protect the public from COVID-19. This would certainly make sense if there was a greater reduction in risk to the public than the benefit received, but that is not the case. Acetaldehyde, it turns out, is not only found naturally in many foods such as fruit, but the FDA allows its presence in cosmetics. Acetaldehyde is also present in alcoholic beverages (regulated by the Bureau of Alcohol, Tobacco, Firearms and Explosives, not FDA) and yet, the dermal limits for acetaldehyde exposure are much lower than limits for internal exposure. To make things even more confusing, the first metabolite created by the body when processing alcohol is, in fact, acetaldehyde. It seems that EPA said it best in the
