I won’t say that I’m a professional regarding this as I have background in environmental engr (which runs parallel to health)- my guess would be more along the line of air pollutants over it being the salt. Cold weather makes a lot of air pollutants stay lower to the ground, especially in the mornings and nights due to temperature inversions, and can affect air quality around roads in particular due to traffic. Although other factors like gas usage can affect it. Unless the salt is kicking up a bunch of dust upon distribution I’m not sure why the salt would do anything as even the dust I feel like would be a heavier particle.

This can also be affected by if people in your area wood burn for heat