As others have said most of that was probably not pollution related to being an ICE vehicle, but if even part of it was the environmental performance of ICEs is magnitudes better over the last 25 years when it comes to unburned hydrocarbons and particulates, which WOULD reduce visible pollution way more than modest EV adoption. CO2 reduction? not so much with bigger vehicles offsetting gains here...

Even modern ICE cars produce lots of particulates and air pollution.

Recent studies have shown significant reductions in mortality starting at 5-10% EV market share.