I’m in a difficult position in this blog post: I have come here to chastise an initiative that has done an enormous amount of good. The campaign to dissuade people from smoking cigarettes has been one of the few truly meaningful successes of public health-awareness campaigns. Many lives have been saved. Unfortunately, some of the arguments used to dissuade people from using cigarettes are deeply misleading and worse, serve to undermine other public health initiatives such as childhood vaccinations and healthy eating.
Consider the following stunning graph:
As shown, while death rates for most cancers have held relatively steady over time, death rate for certain cancers (age-adjusted figures) have varied. None have done so more dramatically than deaths due to lung cancer, which were virtually unheard of prior to World War II, climbed to alarmingly high levels by the 1980s, and reversed dramatically at an almost equivalent rate thereafter.
The single most important risk factor for lung cancer is smoking cigarettes. The reversal in death statistics owes little to new medical treatments or tests, and must be attributed mostly to declining use of cigarettes. This in turn appears to have been caused by two factors: education campaigns and financial penalties (cigarette taxes). I am usually highly skeptical of educational campaigns (human behavior is frankly far more powerfully influenced by unconscious factors), and politically I am opposed to coercive taxation – so in admitting that the tobacco awareness campaigns and taxes have been successful in saving lives, I am responding to data, not wishful thinking.
This good end, however, does not justify any means. I am deeply disturbed when Tobacco-Free campaigns play fast and loose with science in an attempt to be convincing. In fact, certain messages provided by these campaigns may actually be detrimental to public health, even counting the lives saved from lung cancer. Consider the following public service ad:
Executive summary: A biology class is preparing to do a frog dissection, and so each lab bench has a frog floating in a jar of formaldehyde. One student picks up the jar and greedily gulps down the formaldehyde to the horror of her classmates. We are then told that cigarettes also contain formaldehyde, and we are invited to conclude that smoking a cigarette is tantamount to drinking formaldehyde. (A much ballyhooed recent study also touted the fact that e-cigarette smoke may contain formaldehyde as well – though very likely fears of toxin exposure via vaping is completely overblown.)
To be sure, the ad is not incorrect: cigarette smoke does contain formaldehyde. The ad is also correct that formaldehyde is a primary constituent of formalin, a solution commonly used to preserve cadavers. Unfortunately, though, the ad is misleading in a way that strikes at the heart of fundamental scientific truths.
The first truth ignored is that the dose makes the poison. Obviously, smoking a cigarette is not equivalent to downing a whole pint of formaldehyde. According to one study linked above, the amount of formaldehyde in the smoke of a full cigarette ranges from 3.4 micrograms to 8.8 micrograms. According to the material data safety sheet for 37% formaldehyde solution, the LC50 for rats (the concentration per liter that would cause death in 50% of subjects by inhalation) is 578 micrograms over a 4 hour exposure. Compare this again to the 8.8 microgram/cigarette. We’re not in the same ballpark. As for the girl drinking the fictitious pint of formaldehyde in the PSA, the oral LD50 for rats is 500 mg/kg (a rat weighs about a third to half a kilogram; a high school student weighs about 50 kg). Mind you, I’m not recommending anyone try this experiment, nor do I think it’s a particularly good idea to drink anything your biology lab instructor sets out for you, but let’s get a sense of perspective here. There’s some nasty consequences to smoking lots of cigarettes, but it’s a reasonable guess that inhaling a little bit of formaldehyde causes none of them.
The second truth that is ignored is that magical rules don’t apply in the real world. The fact that formaldehyde can be used as a preservative (at high concentrations) does not mean that formaldehyde can have no other functions at lower concentrations and in other environments. A pear, for example, contains about 60 mg of formaldehyde. Human blood contains about 0.1 mM formaldehyde generated internally by the metabolism of certain amino acids. Our bodies constantly produce formaldehyde, though in very small amounts, and these levels never rise particularly high because formaldehyde itself is quickly metabolized to other products which are less harmful. Again, it is not a good idea to challenge this process by obtaining a lot of formaldehyde from exogenous sources, but eating a pear shouldn’t be particularly troubling. Smoking a cigarette is troubling, but not because of the formaldehyde (though inhalation is a far more dangerous method of delivery than ingestion, as indicated by the toxicity statistics above).
Why am I complaining? I don’t like cigarettes – and the ad is certainly gross and therefore probably somewhat effective. The problem is this: formaldehyde in used in some vaccine formulations. According to the FDA, formaldehyde is used to inactivate viruses and alter products of some viruses to render them less dangerous. Residual formaldehyde inevitably remains in the final dose, but at such insignificant levels that it’s ridiculous to worry about. This is made dramatically clear by a number of memes that have attempted to counter misinformation about vaccination:
Thus we have two important public health goals, which have been unintentionally and unnecessarily put at odds with one another: curbing smoking and vaccinating children (and adults with the flu shot). By demonizing formaldehyde at the low doses it exists in in cigarette smoke, the Tobacco-Free initiative has given license to anti-vaccine activists to use the “contains formaldehyde” argument – they have tacitly legitimized that argument. Indeed, by extension, arguments about thimerosal – another sometimes-vaccine constituent which is safe at doses used – gains strength as well.
Beyond formaldehyde, many anti-tobacco campaigns play fast and loose with another popular scientific misunderstanding: they play on people’s instinctive fear of chemicals. As the second formaldehyde meme above demonstrates, a chemical is any molecule, and molecules that are synthesized in a factory and put to some gross-sounding purpose (like embalming using formaldehyde) are nonetheless identical in all respects to the same molecule produced by a natural process and put to some good use (such as the formaldehyde produced by processing amino acids in the body).
The popular figure appears to be 4,000. On a number of smoking cessation sites I’ve looked at at random, I’m told that “cigarettes contain over 4,000 chemicals”. This is presumably supposed to scare me because – chemicals. But the number itself is just meaningless. How many chemicals does a pear have? In a recent blog post I showed the “ingredients” of a banana, and I also reported that cotton has 45,000 genes (each of which must make a protein which is, yes, a chemical).
Often I’m given a list of examples of scary chemicals in tobacco, including everyone’s favorite bugaboo formaldehyde, but without the proper context. For example, even the American Lung Association pulls this crap, telling me not how much of some chemical is in the cigarette, but rather, what other products use that same chemical. Here’s a sample of the useless trivia they give us:
- Acetone – found in nail polish remover
- Acetic Acid – an ingredient in hair dye
- Ammonia – a common household cleaner
- Arsenic – used in rat poison
- Formaldehyde – embalming fluid
Think of the smell of nail polish remover. We’re invited to think that we’re getting that much acetone? Or ammonia. That much? And acetic acid? I enjoy that on my salad along with a little oil, oregano, and pepper. Fear mongering scare tactics are usually the ploy of purveyors of pseudoscience; it is depressing to see such an august institution as the American Lung Association stooping to such cheap tricks.
Some of these sites “helpfully” go on to tell us that of these 4,000 chemicals, some number are known carcinogens. Well, that’s not surprising either. Carcinogenicity is unfortunately often tested with unphysiologically high doses, leading to many chemicals being classified as carcinogens on the basis of unrealistic tests. As the eminent Bruce Ames has argued, unrealistic testing has caused us to greatly overestimate the potential cancer risk of many things we are exposed to. This problem is so significant, that when I see 69 out of the 4,000 chemicals in cigarettes are known carcinogens, my first reaction is to shrug my shoulders and say “Is that all?”
Please, please don’t misunderstand me. We know that cigarettes vastly increase the probability of getting cancer. We know that the number one cancer prevention tool we have in this country is smoking cessation. The importance of avoiding a smoking habit cannot be overstated. Outside of the occasional experimental cigarettes bummed from friends at parties in college, I am a non-smoker and I earnestly encourage anyone I know who smokes to quit and anyone who hasn’t tried it to avoid starting. I also want to be clear that avoiding exposure to formaldehyde, acetone, benzene, arsenic, ammonia, and a great number of other compounds is absolutely good advice. As a neuroscientist, I’ve interacted with many of these chemicals, sometimes in undiluted quantities, and I can attest that being in the same room with them is quite unpleasant.
But I must insist that as we are educating the public about issues of health, we must carefully do so in a way that doesn’t feed into the common misconceptions about chemicals, toxins, and cancer. We must not give fuel to the pseudoscientists out there who are busy demonizing such important advances as vaccination, modern agriculture, and genetically modified foods. That makes our job harder, but it also makes our task righteous. Educating science is a long-term effort, and we can’t lose sight of winning the war for the sake of an albeit important battle.