Before moving into a valley to live, see if you can look across it
from the mountains. Note that on many mornings, there will be multiple
layers of thin clouds or haze across the valley. (You can count five
layers in this picture, including the ground fog.) These are temperature
inversions which trap auto exhaust, industrial fumes, pesticides, and
other toxins in valley air. How prevalent they are will depend upon many
Ground fog is another concern, for if it forms from the moisture of
the ground, it will loft small quantities of whatever is on the ground.
Although fog is good for agriculture; mold, bacteria, and other decay
products that may be lofted by ground fog can be particularly bad for
humans on over-grazed and over-"fertilized" ranch lands.