By Walt Hickey Welcome to the Numlock Sunday edition. This week, I spoke to Chris Ingraham, who wrote a fascinating series of stories about air pollution including “Why dirty air hurts kids more” for The Why Axis. Here's what I wrote about it: The EPA maintains a handbook that looks at all of the benchmarks when it comes to human exposure to chemicals. One somewhat counterintuitive reality is that the younger a person is, the more their exposure to air pollutants has consequences, mainly because on a per-cell basis they're simply breathing more. A 4-kilogram newborn, for instance, breathes