Lunch box - which box is less toxic?

My friends kid is starting school this year and I want to get him a snazzy lunch box for Christmas. My friend is Japanese, so she knows how to pack an amazing bento lunch. I thought it would be fun to get the young-un a fun lunchbox to put it in.

Bento box (a box specifically for yummy packed lunch) are often made of plastic now. I've been reading a lot about the unpleasantness of plastic lately; about the environmental and health issues. So originally I decided not to get plastic lunch.

Then I found an awesome metal lunchbox, but saw that it was aluminium. I read somewhere that aluminium has it's own environmental issues. I've also heard that it builds up in the system and can cause later health problems, especially with the brain. So that's out.

Glass and ceramic are out because he's only 5 years old. Wood is also traditional, but wooden bento boxes are not really strong enough to

That leaves us with stainless steel. I don't know much about this material. I have no idea what sort of environmental impact it has. The only health issue I've seen is a friend with a nickel allergy reacts badly to it.

Now I'm all confused as to what material to get. I want something long lasting that won't have long lasting health consequences.

Is there some sort of system that rates these different materials as to their health and eco-impact? Which is the lesser evil?

The traditional miner's lunchbox (more of a lunch pail, with compartments and innards) was made of enameled steel. They are hard to find and may indeed not be manufactured any more, I have not tried to Google.

They stand up to abuse quite well, although some enamel coating chips off with every serious dent (which takes quite a whack to create).

I have no idea if anybody makes bento boxes of that material; until quite recently, virtually any kind of cookware and eating ware you might want was made out of the stuff in Mexican factories, but I dunno if they ever got the memo from Japan.

What about bamboo or wooden bento boxes?

Justbento

In the end, I went with a Tiffin style box


 He loves it and still uses it almost daily.  

It was so good, I bought the bigger size for each of my friends one Christmas.  We often have a group lunch or dinner and at the end of the feast, they are seeking disposable plastic containers to take home leftovers.  Since I don't buy much food packed in plastic now, I have very few of these.  So I bought them each a giant tiffin and they bring it with them to the feast and use them to transport leftovers home.