I really think it has more to do with humidity. I keep my fabrics away from direct sun light, too. And, no pins get stored in fabrics for long, either.
Have stored for years in plastic, no problems, but I do open them now and again (just to fondle them!) and have not seen any problems. Love to be able to see through the totes
I think plastics are more unhealthy for human consumption than for our fabrics.
IMHO!