I live on the East side of Cleveland downwind from the industrial flats
and our snow is contaminated with soot. I once required large
quantities of distilled water and figured snow was basically the same
thing in frozen form. I needed a new garbage can, so I bought one,
rinsed it out and placed it in the basement. When we had a heavy snow
fall, I carried the can out into the yard and shovelled it full of the
top few inches of snow. I was careful to avoid the lawn underneath. I
carried the can back into the house and later added more snow using a
clean 5 gallon plastic bucket. By the time I had melted enough snow to
produce 20 gallons of water, I saw it was contaminated with a
surprisingly large amount of soot. So the quality of the snow depends
on where you live.

Jim Koch, Cleveland