Michelle is absolutely right.
One of my hobbies is Salt water/reef aquariums and we have had many discussions on reefcentral.com about plastics for water storage and the FDA approved food grade plastic are perfectly fine as they are manufactured specifically to not leach any chemicals out.
I also have a "Vittles Vault" and there is NO NEED TO PUT THE BAG IN THEM. You can dump the food directly in them as they were specifically designed for. These Vittle vaults are great and they definitely seal airtight. After our last dog passed I had Nutro natural in the vittle vault container for about 2 years and when I opened it, it actually still looked and smelled fresh.
here is the description of the Vittles Vault:
"The first absolutely airtight storage container for dry pet foods. No more bulky, awkward bags exposing food to air, excessive moisture and pests. With a spin of the patented lid, the Vittles Vault locks in freshness and flavor. Great for natural foods that are nutrient rich and preservative free. Made of food grade high-impact resistant plastic. The container is square."