Most people think of dangerous levels of ozone gas occurring in traffic congested cities like Los Angeles, so it’s a surprise to find high concentrations of it in pristine areas of the American West. But it’s happening. Two basins that lie along the Green River in the intermountain West have some of the worst ozone pollution in the nation. Reported and written by John McChesney. Edited by Ariana Reguzzoni and Geoff McGhee for the Bill Lane Center for the American West at Stanford University.