I have written this before but consider it important and USA citizens should think more about it:

If you can reduce NOx emissions by 79% for very little cost, should the government legally demand it to be done ?

What about lowering NOx from 79% less to 89% at 100% greater cost?

What about lowering NOx from 89% less to 99% less at 500% greater cost?

What about lowering NOx from 99% to 99.9% less at 1000% greater cost?

What do you say to someone who correctly points out that
when the legal requirement to reduce from 79% NOx to 89% went into effect
it also created more CO2 emissions,
required more importation of oil,
and sucked money away from worthy spending on water pollution,
or developing cures for deadly diseases?

What do you say to the person who correctly points out that there are other relatively cheap ways to prevent ground level NOx from chemically reacting into ground level Ozone?

What do you say to the person who correctly points out that natural rain (or sprayed mists) washes NOx from the air into the soil which fertilizes plant growth?

One can be totally dedicated to science and.wise spending of money and think these questions important.