|"510N e-cigarette and e-liquids" by Lauri Rantala - Flickr. Licensed under CC BY 2.0 via Wikimedia Commons.|
The CDC warns smokers and e-cig users that an oral dose of about 50 to 60 mg of nicotine may be lethal to an adult human being weighing around 154 lbs (70 kg). In reality, the maximum limit was probably much higher than what's previously calculated by a German pharmacologist in 1906. Incidentally, Herr Rudolf Kobert based these estimates on the dubious findings of two men who self-experimented with 4 mg of pure nicotine in the 19th century.
According to Bernd Mayer's research, however, the standard limit for nicotine absorption in adults is probably around 30 to 60 mg, which is equivalent to ingesting five cigarettes or 10 ml of a diluted nicotine-containing solution.
More recent studies have shown that intravenous injection of 5mg of nicotine (equivalent to a 25 mg dose taken orally) lead to only mild symptoms of nausea and coughing.
Post-mortem examinations of people who have died from nicotine poisoning suggest that lethal doses of nicotine could be 20 times higher than the 60 mg limit.
But, neurologist and nicotine expert, Dr Jacques Le Houezec, thinks at least 500 to 1000 mg is a more prudent estimate. Meanwhile, nobody has figured out yet the maximum amount of nicotine in e-liquids that can be absorbed by the human body through inhalation before an adult of average height and weight experiences the typical symptoms of a nicotine overdose.
Contrary to popular belief, nicotine isn't the primary cause of lung disease in smokers. Carcinogenic compounds in tobacco are very much to blame. Moreover, it's equally fallacious to think that an e-juice is now a toxic fluid just because pure nicotine was added to the dilute solution. (Some people in the anti-vaping brigade seem to think so.)
Better err on the side of caution by wearing gloves, goggles, face mask, and apron when handling pure liquid nicotine. It's so toxic that having a small amount of liquid nicotine absorbed by your skin would be enough to make you ill.
Mayer's guest editorial for Archives of Toxicology was an interesting read. He ended the well-written short piece with the following proposal:
"…Frequent warnings of potential fatalities caused by ingestion of small amounts of tobacco products or diluted nicotine-containing solutions are unjustified, and need to be revised in light of overwhelming data indicating that more than 0.5 g of oral nicotine is required to kill an adult."