I think it depends on how far you want to go. People do use treated wood for vegetable beds and they don't die soon after eating the vegetables. But long term effects are unknown. But that goes for redwood and cedar too. Just because they're "natural" doesn't make them safe any more than "chemical" means unsafe.
My yard soil, being an urban house, probably has more toxic stuff in it than treated wood has. IMO there's a kind of bottom line that I don't live in a pristine environment and that's just the way it is. Even
"organic" soil can have some nasty stuff. It's all relative.
I do prefer concrete block to wood however and line the inside with plastic. The block is longer lasting, easy to reconfigure, reusable, and way easier to build beds with imo.