Penta was banned by EPA in 2015 according to Google AI search. 10 yoa lumber exposed o elements, my swag, probably a lot of the chemicals have leached out ( using 2015 date ) . My understanding , may be completely off base , no expert , is that so called pressure treated , isn't truly "pressure treated " but only soaked in the preserving chemicals , allowing the chemicals to leach away fairly easily.
Take all my comments for what their worth , a little less than 1/2 what you paid for them .
I got out of a related industry in 2016 so I checked the EPA site for current status. Below is from the EPA website:
Use of PCP is being phased out over five years beginning in 2022. Until February 29, 2024, registrants may continue to produce, sell, and distribute wood preservatives containing PCP while wood treatment facilities transition from PCP to alternatives. After that time, wood treatment facilities will be allowed to use their existing stocks of PCP to produce treated wood until February 28, 2027.
