How not to think about risk

Here’s a story that is both totally absurd and a lesson on how not to think about risk. In the early nineties, the US Environmental Protection Agency got into a fight with a company over a toxic waste dump in New Hampshire. The company had already spent a fortune cleaning the site up. They’d removed enough toxic chemicals that a child could safely play there and even eat small amounts of dirt 70 days a year. But the EPA weren’t satisfied. They wanted the chemical levels lower. So low that it would have cost another $9.3 million, and left the site clean enough that a child could safely eat the dirt 245 days a year. But the site was a swamp, there were no children, and no one lived anywhere near it.1 This craziness comes about because we often treat risk as if it’s a physical property of an object, like its weight. Toxic chemicals are risky, so we must reduce the chemicals. But that’s not quite right. The sun is a giant nuclear furnace; it’s objectively pretty dangerous. But you aren’t…