The box I cobbled together from old pallets, dirt is a mix of potting soil and local dirt spiced with chicken poo.
For the more observant viewers, you may notice that the closest 'V' is slimmer than the upper square -- the pallets were a little short. I plan to plant smaller vegetables in those areas.
Some people like to avoid ALL chemicals they can in their garden.
You can also just line the wood with plastic and it’s moot, but as a generic basic around the globe advice.
Dont use pallets or treated wood for crafts and stuff in your home.
CCA is banned for lumber designed for ground contact construction. Pallet wood has no restrictions. Pallets use in shipping means you don't even know what country it came from.
Stuff like telephone poles still use it I believe. At least in Canada. Railroad ties too likely.