 Well, first of all, remember, pollution does not respect borders. So maybe if we called it migrant pollution, Republicans would care about it. But anyway, this is for pollution that drifts downwind across state lines. Imagine if you're sitting behind a polluting truck and you get a tailpipe full of their pollution into your face. That's what downwind states are facing. And it also makes it harder for downwind states to meet their own ambient air quality rules under previous laws.