Lads, this happened for a single day, it was lovely but is not a regular event. The city still has pollution issues however many now agree that it's caused from burnings that occur in northern India.
I've lived here since the earthquake, have only seen Everest from my rooftop in the capital one single time.
There are about 99% fewer vehicles on the road as we are in complete lockdown however the brick kilns that are located in the valley are probably the bigger polluters. Local neighbourhood garbage pickup guys regularly burn plastic.