We have a vegetable garden. Our landlords just had a new roof put on the house and the roofers scraped some of the old material off and into the vegetable garden. My wife is worried about whether the vegetable will be edible. The tomatoes and zuchinni is still growing and not nearly ready for harvest yet. The old and new roof are composition shingles.
Thanks for writing! This is a great question --- and one I don't eally have an exact answer to.
I've done some research on this and have not run into any research pointing to problems with roofing shingles leaching out harmful materials. By nature, shingles are designed to last a very long time, which should make them highly resistant to leaching large quantities of anything.
Picking up/raking any large pieces from the soil should be all you need to do.
---Justin, Senior Garden Editor, BHG.com