Was Nietzsche right?

In recent weeks there’s been a furor in the Washington D.C. area over lead in the District’s water supply. Today, the Washington Post (registration required) looks at why lead is bad for you and covers some of the science and public policy. That lead is bad for you is open and shut. Too much lead kills you and for kids, too much is not that much. But I am skeptical of recent studies that find that the worst effects of lead happen at the lowest levels of exposure.

Here‘s a typical newspaper account of one of those studies and a quote from a leading researcher on the topic:

“There is no safe level of blood lead,” said Dr. Bruce Lanphear, lead author of the lead study presented Monday at the Pediatric Academic Societies annual meeting.

Edward Calabrese would not agree. Calabrese is a toxicologist at UMass-Amherst and a leading scholar of hormesis, the phenomenon that most if not all toxins are actually good for you at sufficiently low doses. This does not imply that you should start adding mercury to your eggs or lead back into your pots. But the impact of toxins appears to be U-shaped–good for you at sufficiently low levels then bad as exposure increases. Whatever doesn’t kill you makes you stronger.

Hormesis also implies that linear models or threshold models of toxic impact are misspecified and understate the impact of toxins over some ranges of exposure.

Here’s a Scientific American article on Calabrese and hormesis.

Here’s my take on the economics and policy implications of hormesis.