Assessing the impact of lead exposure is difficult if individuals select on the basis of their characteristics into environments with different exposure levels. We address this issue with data from when the dangers of lead exposure were still largely unknown, using new evidence on intelligence...

The Clean Water Act (CWA) significantly improved surface water quality, but at a cost exceeding the estimated benefits. We quantify the effect of the CWA on a direct measure of health and incorporate health benefits into a cost-benefit analysis. Using a difference-in-differences framework, we...