This is so weird - I have had plastic bags stored for years and never thought a thing about it. Yesterday I read this thread. A friend of mine is gifting me her entire sewing items. In a plastic drawer set was a drawer full of little plastic bags, the ones smaller than 12 inch squares. It was obvious they had been in there for years! So I was pulling them out to put in a recycling bag (we take them to the grocery store to have them restyled) and one shattered. No other way to describe it - the little bag looked like it broke into so many tiny pieces and most looked like little shards of glass. They weren't sharp they only looked that way. Until I read this thread I had no idea this would happen.