Some externalities are hard to tax. For example, consumption of red meat probably increases cancer risk [1]. We can't introduce a tax on cancer, but we still want to reduce the occurrence of cancer, so all that's left is taxing red meat.
If someone with cancer dies, their cancer also dies. Net result: less cancer. (Unless it is important to research, such as HeLa. In that case, the cancer can go on living with all expenses paid, and the human it came from can be forgotten, and their estate uncompensated.)
~ (Poe's law: insincere.)
-- The Tragedy of the Commons
I recommend the whole paper as a good think on the unintended consequences of not biasing the options of people away from collective irresponsibility.
You might not care about some health risk, but when you get sick, your family is going to be affected, your coworkers are going to be affected, and society has to pay for you to get well (by paying more for health insurance).
And we're social animals. We care about one another. And caring sometimes means that we nudge people into a direction that makes them healthier.
(I don't actually know if red meat is dangerous enough to justify a tax, but for the sake of argument, let's assume it is)
But secondly that WHO page is frequently cited by people who apparently haven't understood the numbers behind it. It's not worthwhile to tax meat as a cancer risk because the health impact is a rounding error.
According to the WHO:
> about 34 000 cancer deaths per year worldwide are attributable to diets high in processed meat.
That's the population of a village worldwide. To turn that into a death rate for the world population in 2015 is 34000/7400000000*100000 = 0.45.
That wouldn't even make it onto this table[1] of most common worldwide death rates. You can see rates like 15 for diabetes, and 115 for heart disease, both of which are strongly linked to diet.
If everyone in the world adjusted their diet so they wouldn't be overweight or obese, but kept eating processed red meat, then diet-related illnesses would be rare enough that nobody would even bother talking about them, as opposed to being the one of the leading causes of death in the western world.
Citing a WHO report which says that evidence of carcinogenicity is strong without context is correct but misleading. As that page points out you can have strong evidence but tiny effect sizes.
1. https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rat...
I could just as well have said that red meat increases risk of heart attacks, red meat increases choleserol, raising cattle for meat uses lots of fresh water in areas that don't have enough, that a lot of feed is required to produce very little meat...
It just happens that one externality (methane emissions) is easily measured, but all the other externalities of meat consumption are not, hence a tax makes sense.
E.g. are we going to tax farmer John more than farmer Bob because John feels he needs to smoke cigarettes while farming (and thus makes some small extra contribution to CO^2 emissions), no. Measuring things at that level would be silly.
But it's easy enough to get sufficiently right for the purposes of discouraging externalities and encouraging innovation. Farms, power plants, cargo ships etc. are all major contributors to pollution, and the taxes they pay can be calculated as a function of regular inspections, which all those industries need to undergo anyway.