Also in Slate, Brian Palmer explains how a drug makes it onto the World Anti-Doping Agency’s list of banned substances.

The British tabloid News of the World published a photo Sunday of Michael Phelps taking a bong hit at a college party. The International Olympic Committee accepted the swimmer’s apology for his behavior, and so far Phelps’sponsors are making light of the incident. Meanwhile, on blogs and chat forums, fans are wondering whether Phelps’ abnormally large lung capacity means he can take monster bong rips. Can he?

He can. Total lung capacity refers to the volume of air contained in the lungs at the point of “maximal” inspiration—i.e., the biggest breath you can take. It’s measured in liters. The greater a smoker’s total lung capacity, the more he can inhale from a given joint, bowl, or bong. According to some estimates, Phelps’ lung capacity is twice that of the average human, or 12 liters rather than six. So if he puts his mind to it, he can take a hit that’s twice as big as that of the next partygoer.

Each time a smoker takes a puff of marijuana, THC is delivered to the circulatory system via the capillaries in the lungs. The rapidity with which a smoker gets high depends, in part, on how quickly he absorbs the THC, which depends, in turn, on the interval between puffs, hold time, and, yes, lung capacity. But this doesn’t mean that Phelps gets twice as high, twice as fast as non-Olympians. Larger people need more cannabis than others to feel its effect. (Phelps is 6-foot-4 and weighs about 195 pounds.) How quickly a smoker gets high, and how high he gets, also depends on whether he’s a regular user. Veteran tokers need to smoke more than novices to experience the drug’s physiological and behavioral effects.

The long-term consequences of marijuana use are still hotly debated. But there’s some evidence that users suffer from decreased lung capacity and may develop chronic bronchitis and airflow obstruction. Continued use would likely have an adverse effect both on lap times and bong-hit size.

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Explainer thanks Lester Grinspoon of Harvard Medical School. Explainer also thanks reader Greg Wymer for asking the question.