I don’t quite know the meaning of the term “public health.” Googling the definition hasn’t helped me, because in context its definition is never consistent. The Google definition is “the health of the population as a whole, especially as monitored, regulated, and promoted by the state.” Maybe this vague definition is the right one, because whenever there is some kind of general health problem (like rising obesity or drug overdoses) the argument for government intervention always starts with “This is a public health issue!” Notice that this isn’t really an argument, in the sense that it’s totally circular.
I think “public health” ought to mean something like, “health issues by which one actor can affect the general health of the population.” Basically it should be a reference to the effect of a person’s behavior on *other* people’s health but not his own. This is actually a radically different definition than the one Google gives and the one that (I *think*) most people have in mind when they use the term. If I over-eat, or adopt a dangerous drug habit, or smoke, or skateboard, then it’s not really a public health issue. In those cases I’m only harming myself. Contrived counterexamples aside, none of those behaviors significantly affects “the public.” A single instance of, say, a risky prescription painkiller habit only affects the user. I don’t think it’s meaningful to count up all the individual instances of “private health” problems and say that the summation converts it to a “public health” issue. One person deciding to roll the dice with his own existence is a private health issue; a thousand (or a million for that matter) doing the same is *still* a private health issue, just one that many people have in common.
On the other hand, if I drive recklessly, or dump pollutants into the drinking water supply, or fail to immunize myself or my children, or if the government implements a policy that makes food or medicine very scarce, these could legitimately be called public health problems. They are instances of one party’s behavior affecting another party’s health. Some kinds of intravenous drug use could also be considered public health issues, considering that these drug users are extremely prone to blood-borne pathogens that find their way into their sexual partners or people who share their injection equipment. One could quibble about how in some of these cases the relevant “public” voluntarily puts itself at risk and in others it doesn’t, but at least in this case including the word “public” in “public health” is meaningful.
I recall sitting through a debate on drug legalization. The person who was pro-legalization finished his argument, and a person behind me said indignantly to her friends, “He’s ignoring the public health issues.” No, he was not. He was explicitly arguing that individuals have the right to harm themselves; they have the right to put whatever chemicals they like into their own bodies. (He also gave the other standard arguments for drug legalization, which I won’t list here as I’ve discussed them in detail elsewhere.) He was arguing, without exactly using my terminology, that there is a difference between public and private health, and that you don’t convert the former to the latter just by adding up the instances across a big population. The confused person behind me was trying to ignore this difference. She was trying to conflate two different things and paper over the difference by adding the word “public” to the word “health”. (Perhaps she had in mind that intravenous drug users infect their partners, in which case I’m being terribly unfair for the sake of making my point. But this was not the only time I’ve heard “public health” used in this manner, so I won’t refrain from using this as an example.)
I think there are four different types of health issues that vary in their degree of public-ness, and they should all be treated separately. We should drop the term “public health” altogether and explicitly state what kind of issue we are talking about. The first of the four kinds is the situation in which my behavior harms myself and no one else (or the harm to others is minimal at any rate). I dedicated a paragraph to this above, so I won’t belabor the point here.
The second kind is the situation where I can control my own exposure to the risk. If I have promiscuous sex or engage in IV drug use with shared needles, then it’s true that someone can harm me. But I can *decide* whether I’m exposed to this risk or not. It’s perfectly fair to treat this as a kind of public health issue, because you may want to know how these kinds of infections spread and how to stop them. However, we need to keep in mind that these populations consent to the risks they are taking. Another example is a polluting factory that is the only source of economic value for a community. Let’s suppose (not unreasonably) that everyone in the town has the opportunity to move away if they wish to. Everyone is there of their own volition. Living near a polluting factory is worth the cost of inhaling pollutants, because you get to work in a factory or sell goods and services to the factory workers. It may be meaningful to call the factory a public health hazard, but it needs to be kept in mind that everyone is better off *with* the factory than *without* it. Also consider driving. Not reckless driving, but normal driving. There is a non-zero chance that you will kill someone every time you drive somewhere, but everyone consents to this risk under the assumption that everyone else obeys various safe driving practices (obey traffic laws, avoid debilitating drugs, etc.). It would be great to reduce the risks of these behaviors, but keep in mind that taking these hazards as a given, people consent to them. People engage in recreational drug use or normal driving or live near factories because, in their view, the benefit is worth the risk.
A third kind of health issue is one where you can affect someone’s health involuntarily. Suppose the IV drug user above doesn’t inform his wife about his habit and infects her with HIV or hepatitis. Or suppose a factory agrees to abide by zoning laws and pollution regulations, but then clandestinely dumps a dangerous dose of pollutants into the water supply. Or suppose someone drives their car extremely recklessly, perhaps while under the influence of drugs. It’s fair to say these are all public health issues, because a party is causing harm to a non-consenting party. These are cases where the actor who does harm could restrict their contribution to the hazard, but chooses not to. The harmed party can’t reasonably restrict their exposure to the hazard. There is a “bad guy” in this story, and it’s fair to sanction these kinds of behaviors so as to limit the hazard. Moreover, unlike in the next case I will discuss, sanctioning the hazard-producer *works*.
A fourth kind of health issue, and one that I consider true “public health”, is the spread of communicable diseases. My case of the IV drug user above is slightly different, because those were cases where someone can limit their exposure to the risk *or* their contribution to the risk. There isn’t necessarily malice or recklessness in this fourth case, as in the case of the polluting factory or reckless driver. There isn’t necessarily a villain, just normal people going about their lives within a population exposed to some infection risk. These are situations where it’s nearly impossible to limit your own exposure to the risk or your contribution to the risk. The instructions for the former are “don’t breathe in” and the instructions for the latter are “don’t breathe out”. Or perhaps there is a less extreme possibility such as “become a complete shut-in,” but let’s suppose that’s so impractical that it’s not really an option for most people. These are the situations that truly justify a public policy. That’s not necessarily to say a government policy. It could take the form of suggested travel restrictions, rather than mandatory ones. Or a billionaire purchasing vaccines and giving them away, as Larry Page did for every child in San Francisco. Never mind that, I’m not going to stand on libertarian principles here. If ever there is a good case for government intervention, this is it. There is a true public good/collective action problem in limiting communicable diseases. The point is not that the travel restrictions protect the individual who obeys them, or that the vaccines protect the vaccinated. The point is to disrupt transmission in general. This forth kind of health issue is one where population effects are important and large. The one-off bilateral transmissions take a back-seat to these bigger population effects. There are tipping-points, by which reaching some threshold of infected people dramatically increases the risk of further infections. There are herd immunity effects, whereby achieving a certain level of immunization (either with vaccines or with people surviving prior infections) dramatically reduces the risk of a pandemic. This is very different in kind from bilateral harms like “I drive recklessly and hit you with my car” or self-harm like “I engage in risky drug use and accidentally kill myself.”
Above I have discussed four very different kinds of health issues. I think we should stop papering over the difference by referring to all of them as “public health.” These different issues have very different policy implications. I did once encounter someone who didn’t accept the difference. He insisted to me that smoking was a public health issue because having friends who smoke makes it more likely that you will smoke. Smoking, in this framing, is more like a communicable disease and less like a choice. I don’t buy his framing of this particular issue, but I won’t discuss it in detail because that’s not the argument I’m making with this post. I simply want to acknowledge that these four categories might overlap somewhat and that it might be ambiguous which category is appropriate for a given issue. We should be explicitly talking about which category applies. And that’s exactly the discussion that people are dodging when they promiscuously recite the magic words “public health.” I think people just lazily use this term when they want the government to do something about the problem, because “public” sounds like it means it’s happening to all of us. That’s not right. The “public” in “public health” often just means “I counted up instances of private health problems over an entire population.” Simply adding one word to another word does not conjure policy implications out of thin air. That would require making some kind of argument.