I faced the same question when it came time to build my raised beds.
The conclusion I came to was, here I am doing my best to garden
organically, not using pesticides or artificial fertilizers, yet I
was considering surrounding my plants with chemically treated lumber?
Even if it was trace amounts of arsenic, why take that chance? I bit
the bullet and spent the extra dough on redwood, which is naturally
rot resistent and beautiful to boot. I'm very glad I went the way I
did. But only you can make that decision for yourself.

Good luck.

-Fleemo