> The study followed the same individuals as air pollution varied from one year to the next, meaning that many other possible causal factors such as genetic dif

> The study followed the same individuals as air pollution varied from one year to the next, meaning that many other possible causal factors such as genetic differences are automatically accounted for. That's already much better than what I had feared. Not perfect, of course, but better than the usual "corellation == causation" journalism.