So you’re worried about plastic decomposing under heat and leaching strange chemicals into your food? All I can say is: that’s perfectly reasonable.
No sane “science” will tell us yea or nay on this one for another fifty years, or indeed ever, since we cannot mathematically isolate this factor, unless we find someone who literally has eaten all food out of tupperware and had no other environmental influences.
So in the meantime, we’re left with instinct and mine is: stick to what has been in use the longest if you want to minimize environmental toxicity.
Here’s the first part of your solution: pyrex bowls. You can find them at Bed, Bath and Beyond, which although all your hip friends tell you it’s a giant tower of corporate and possibly (gasp) Republican doom, is the best place to buy these things.
The three bowls are reasonably sized: the hugest is a 4 quart bowl that’s about the size of a salad bowl you’d use to serve a party of eight, the middle is a 2.5 quart bowl that is about the size you’d use to marinate a couple steaks for barbecue, and the “smallest” is a 1.5 quart bowl that will fit comfortably a meal for four people that got cooked and then not eaten because pizza arrived that your teenage daughter ordered.
True, the lids are plastic; however, nothing seals better than a flexible substance, so plastic is your option if you want a tight seal. Try not to pack them to the rim, and it won’t touch your food. Seems a reasonable compromise to me.
Here’s another, this time from what all your urban friends will agree is the world epicenter of Satanic industrial might, Wal-Mart. Although they’re showing the set and don’t list it, you can get the 1 quart flat-bottomed piece for $6, which is a good deal. Flat-bottomed is important: if you have leftovers which need to sit flat, like lasagna or enchiladas, this’ll do it.
Next time someone tells you about how plastics are killing us all, remember a balance between idealism and reality: buy sterile, non-leachy pyrex for your containers, and let the lids be plastic. This is a realistic response and one more thing you can cross off your list of modern terrors.