There are two problems with cars; the exhaust gas and the particles in the exhaust. The gas part was fixed almost 40 years ago, in 1975 when catalytic mufflers were added to cars.
The particle part used to exist with Diesels. Today diesels use a particle filter on the exhaust. The air is very clean.
This is over-simplified of course. Many things went into fixing the exhaust problems. The replacement of carburetors with fuel injection systems, the use of lower sulfur fuel, oxygen sensors, computers, lean burn engines, more efficient engines, multiple valved engines compared to two valve types, nox sensors and a host of other ideas and products have made exhaust almost unbelievably pure.
As a result of the all of the work and the products, the exhaust from vehicles is almost safe enough to breathe. Global Warming is over. It’s been fixed. Global warming is no longer a problem, at least not in America, Europe , Australia or Antarctica. We live in a Green World thanks to science.