A crew at the shop recently sampled soil at a private school's playground. The equipment was built out of PT timbers in the early 1990s, when CCA (copper, chromate, arsenic) was still in use.
All of the arsenic hits were above health based criteria for direct dermal soil contact.
Way higher than any naturally occuring background levels.
Since then, maybe 2002, CCA has been replaced with a different compound. Not sure of it's chemistry or mobility, but obstesibly less harmful. I recommend a solid shot of the googlez and DYODD.