It's all about particle size and if the aerosol is larger than the mask can pass, it will be stopped. At .3 microns, COVID aerosol can pass through, but the cloud density would have to be high for a large amount to get through and N95 masks are supposed to stop 95% of it. With any breeze, the cloud will disperse well enough that it really should't be a problem for most people unless they're in its direct path.
There was never any attempt to stop ALL of the airborne particles, it was about reducing the intake enough to prevent serious illness.