text:  You know, back, I guess it was in the 70s, whenever they came out with the, they legislated, I think they called it like the Clean Air and Water Act, and they began to put, as you know, what they call catalytic converters, you know, on cars, I guess, to reduce emissions. And then plus they quit offering leaded gas. Now it's unleaded gasoline. So it seems to me that alone really significantly cleaned up