I wouldn't worry, if tupperware fumes (or anything else that might burn in the kitchen) were toxic my poor babies wouldn't have lasted a week in my house


Edit: I should mention that once I was cooking in the oven and hubby's hard plastic lunch box was on the burner where the oven vents. I left the kitchen and returned quite a while later to discover that I had completely melted hubby's lunch box. It stunk something awful, but we're all still ok