This is one of those questions that we each have to answer for ourselves, in my opinion. Personally, I would not use anything that I thought had been pressure treated near food crops. Other people I know build raised beds out of pt wood, and they seem to survive pretty well. Who knows?

Making this decision involves asking why you're growing peas in the first place - if one of the main reasons is to be sure you're getting healthy food, then you have your answer.
If I were in your situation, I'd use the trellises in the flower beds and find some simple netting for my peas. You really need to decide for yourself, though.

If you decide to replace them you have a lot of choices now instead of pressure treated. I've got a couple of trellis and they are made from PVC and are white in color. I got them because they don't need to be painted and hold up great never rotting (they aren't near food crops). At the time I bought mine they were hard to find but I am sure now if you look there are more of these type of trellis out there.