We get this question a lot. Here’s what it says on Tom’s of Maine Web site:

We use 100% aluminum tubes because they are environmentally sensitive. They are recyclable in most communities. They also help maintain our natural flavors. The tubes that we use are lined with a thin layer of food-grade plastic (meaning a pharmaceutical grade inert epoxy which is approved safe for use with food ingestibles) that prevents the toothpaste from coming into contact with the aluminum.