I did some blasting outside this fall. I used a fresh air system and a blasting hood. I don't think there is a problem with any of the blast media being left where it falls in the woods. I will say though that you will use more media than you expect so using a tarp is the way to go so you can collect/sift it and reuse it. I got mine from Harbor Freight. Was the cheapest I could find and delivery was just a few bucks. They have descriptions of the different media on their site. More options than I knew of.

Dennis

40 Chevy 1/2 ton