Looks good!

You should be fine since most of the arsinic has been removed from from modern pressure treated lumber. They changed what they used to be less toxic. Also rats can smell the lumber and know it will be bad to chew on it before they do. Might actually be a good thing as they will not be chewing on it. We used regular lumber in ours and have not seen any signs of them chewing on the wood. We have had three tubs with chew throughs and only one had an escape, but we found all three girls that had been in that one so it was a non issue in the end. (Other than the bites to my hands from having to get a little rough with one that was persistant. )

If it does worry you the option of painting it to keep direct contact from occuring always exists!