How Toxic is Nicotine?
Thanks to some scientific sleuthing courtesy of a dedicated toxicologist, nicotine may have to surrender its infamous position.
This article originally appeared in the Newton blog on RealClearScience. You can read the original here.
Nicotine, the addictive ingredient in cigarettes, can be quite a lethal compound. It's widely recognized to be deadly at doses between 30 and 60 milligrams, making it more dangerous than both arsenic and cyanide. But thanks to some scientific sleuthing courtesy of a dedicated toxicologist, nicotine may have to surrender its infamous position.
Dealing with toxins by trade, Bernd Mayer at Karl-Franzens University in Austria was well acquainted with nicotine's standing, but also irked by the lack of evidence for it. So he took it upon himself to trace the estimate's source. At first, his quest stalled.
"Literature and Internet searches provided circular and often misleading references to databases or textbooks, which either simply stated the dose without reference or referred to another textbook and so on," he lamented. Even the Centers for Disease Control cited dubious sources, Mayer found.
Persistent, Mayer began screening German scientific literature published before World War II, and soon started noticing references to a compendium of intoxicants assembled by prominent German pharmacologist Rudolf Kobert in 1906. It was in the dusty pages of a chapter on nicotine that Mayer found his biggest clue yet:
"The lethal dose of pure nicotine is... difficult to determine," Kobert wrote, "because it easily decomposes a bit and, on the other hand, mostly contains more or less water; however, in accordance with the severe symptoms evoked in several experimenters by 0.002-0.004 g it is certainly not going to be higher than 0.06 g."
Mayer knew he was on the right track.
"It is beyond any doubt that this short, not particularly convincing paragraph represents the genuine origin of the lethal nicotine dose we still refer to more than 100 years later," he said. Clue in mind, Mayer further unraveled the mystery, uncovering the experiments Kobert referred to in his textbook.
Sometime in the 1850s, two German experimenters, known only as Dworzack and Heinrich, took it upon themselves to discover what would happen if they directly consumed nicotine. Here's what happened, as described by Austrian pharmacologist Carl Damian von Schroff in 1856:
"These authors felt a burning sensation in the mouth, scratchy throat, increased saliva excretion, followed by a feeling of warmness emanating from the stomach, which spread over the chest and from the head to the toes and fingertips. Afterwards the subjects became agitated, suffered from headache, dizziness, numbness, cloudy vision and hearing, light sensitivity, anxiety, dryness of the throat, coldness of the limbs, ructus [belch], flatulence, nausea, vomiting and rectal tenesmus. Respiration was accelerated and labored, pulse rate increased initially, and rose directly with the increasing dose; but later rose and fell erratically. After 45 min the experimenters lost consciousness. One of them suffered clonic seizures for 2 h, particularly of the respiratory muscles, also tremors of the limbs and shivering over the whole body."
The account is remarkably consistent with what we now know of severe nicotine poisoning, but it deviated from the facts in one key respect. By the self-experimenters' reports, this deleterious chain of symptoms was set in motion after they ingested a mere 4 milligrams of nicotine. For comparison, that's roughly equivalent to the amount absorbed after smoking just four cigarettes! That can't be right. With 43.8 million regular smokers in the United States, we should be seeing a terrifying outbreak of seizures and tremors. We're not. This shoddy account is obviously incorrect, yet it appears to be the sole basis for nicotine's estimated toxic dose!
Nicotine is, without a doubt, one murderous compound. When concentrated, it's corrosive to soft tissues, and targets the nervous system with frightening speed. But despite it's deadliness, common knowledge needs revision. Citing studies conducted in dogs, Mayer recommends updating nicotine's lethal dose to between 0.5 and 1 gram for the average person -- approximately 15 times the previous value -- but urges that new studies be completed to cement correct information into the scientific literature.
Source: Bernd Mayer. "How much nicotine kills a human? Tracing back the generally accepted lethal dose to dubious self‐experiments in the nineteenth century." Archives of Toxicology. Oct. 2013. DOI 10.1007/s00204-013-1127-0
(Image: Cigarettes via Shutterstock)
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Whether or not women think beards are sexy has to do with "moral disgust"
- A new study found that women perceive men with facial hair to be more attractive as well as physically and socially dominant.
- Women tend to associate more masculine faces with physical strength, social assertiveness, and formidability.
- Women who display higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, are more likely to prefer hairy faces.
Beards and perceptions of masculinity<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg0MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzkxMjM3N30.cH-GqNwP5GVqvstgJWAhBPn1B_lYpVEAI0I7iax7EQw/img.jpg?width=1245&coordinates=0%2C1900%2C0%2C849&height=700" id="caae6" class="rm-shortcode" data-rm-shortcode-id="cb0a355a4e8e1899789bc45f3f7aef56" data-rm-shortcode-name="rebelmouse-image" />
Photo Credit: Wikimedia<p>The study used 919 American (mostly white) women ages 18-70 who rated 30 pictures of men they were shown with various stages of facial hair growth. The photographs depicted men with faces that had been digitally altered to look more feminine or more masculine, with a beard and without a beard. The women rated the men according to perceived attractiveness for long-term and short-term relationships. The study found that the more facial hair the men had, the higher the men were rated on their attractiveness, particularly for their suitability for a long-term relationship.</p><p>Part of this might be attributed to facial masculinity — i.e. protruding brow ridge, wide cheekbones, thick jawline, and deeply set narrow eyes — which conveys information to a woman about a man's underlying health and formidability. Women tend to associate more masculine faces with physical strength and social assertiveness. It can also indicate a man with a superior immune response. The researchers suggested that their findings favoring bearded men could be due to the fact that facial hair enhances the masculine facial features on a man's face, like creating the illusion of a thicker jaw line. This could communicate direct benefits to women like resources and protection that would enhance survival among mothers and their infants. In other words, while a beard doesn't mean superior genetics in and of itself, it might be a primitive, ornamental way of saying, "Hey girl, I'm a testosterone-fueled lean, mean, pathogen fighting machine." <br></p><p>It could also be that a beard becomes its own destiny. The researchers in this study cite prior research that found that by growing a beard, men felt more masculine and had higher levels of serum testosterone, which was linked to a higher level of social dominance. They also tended to subscribe to more old-school beliefs about gender roles in their relationships with women as compared to men with clean-shaven faces.<span></span><br></p>
What does disgust have to do with beard preference?<p>Obviously, not all women dig beards. The researchers were particularly interested in what traits make a women prefer bearded men over clean-shaven faces. They looked into several factors including a woman's disgust levels on various concepts, her desire to become pregnant, and her exposure to facial hair in her personal life. </p><p>According to the study, women who were not into facial hair were turned-off by potential parasites or other critters they imagined could be in the hair or skin. Women ranking high on this "ectoparasite disgust" scale might have viewed beards as a sign of poor grooming habits. However, women who ranked higher in levels of "pathogen" did find the bearded men to be desirable, possibly because they perceived beards as a signal of good health and immune function. An intriguing discovery in the study was links to morality. Women who displayed higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, were more likely to prefer hairy faces. The authors opined that this could reflect a link between beardedness, politically conservative outlooks, and traditional views regarding performances of masculinity in heterosexual relationships.</p>
Additional findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg1My9vcmlnaW4uZ2lmIiwiZXhwaXJlc19hdCI6MTYyNDI1NjUyOX0.P9B8WbmJR0q4nfzYZKbuNSA-2SAigVWJgrQE-_Gxlds/img.gif?width=980" id="49143" class="rm-shortcode" data-rm-shortcode-id="2ed3b1d6f20fc170bf2974646e565e8d" data-rm-shortcode-name="rebelmouse-image" />Giphy<p>The correlations that existed between married and single women's rating on the attractiveness of beards were not particularly clear, although the researchers noted that single and married women who wanted children tended to find beards more attractive than the women who didn't want children. They also found that women with bearded husbands found beards to be more attractive, which might indicate that social exposure to beards influences how desirable they are perceived of as being. Or it could be that men with wives who like beards grow beards.</p><p>It's important to note that culture plays a huge role in how attractive women perceive certain male characteristics as being. This study looked at a small, culturally specific group of American women, so no big, universal claims should be made about masculinity, facial hair, and male desirability to women. However, research like this is important in highlighting how human grooming decisions are driven by much more than fashion trends. Sociobiological, economic, and ecological factors all play a part in the way we choose to present ourselves.</p>
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