As I understand it, there are perhaps four major pollutants coming from our collective tailpipes. CO2, a greenhouse gas that I try hard to emit less of. There's CO which is lethal in large concentrations, but I figure it's harmless in small doses. HC, which is toxic, but eventually degrades in the ecosystem. I emit a little of on a cold start. But my HC emissions should be very small otherwise, because I keep my PCV system in good condition, and I don't fill my EVAP canister with liquid fuel. I chose an electric lawnmower partially so as not to have to deal with HC emissions there. I've made up my mind on those three pollutants. I'm not so sure about NOx. It's a major contributor to smog and acid rain. But Buffalo, NY, where I live, very seldom sees smog. Same with the thousand miles of small towns, farms, and forests downwind of me before my pollution passes over the Atlantic. Acid rain? I'm not worried. The soil downwind of me will survive a pH adjustment, even if it means we get different kinds of trees in some areas. The reason I bother to ask is, we all make decisions on NOx versus CO2. Running an engine at heavy throttle, low RPMs creates more NOx and less CO2. So does lean burn. New vehicles can only achieve better EPA bins at the expense of FE and CO2. So, given my geographic location, is the SULEV CVT Insight a greener car than the LEV Insight with lean burn? What's the range and timescale of damage done by NOx? Are there any other reasons I should reconsider my prioritizing CO2 over NOx?