Is Tupperware safe?

Does anyone know if Tupperware is safe to use? My son started Kindergarten this year and I'm trying to find ways to be more 'green' with his lunches and hate using Ziplocs. What about Rubbermaid containers? I'm not familiar enough with which plastics are safe and which are not. He has a Crocodile Creek lunchbox that he loves, so I don't want to have him change to a Laptop Lunch if he doesn't have to, so wanted to explore other options.

Thanks so much!!!

Stacy
Mom to three beautiful boys!!!