"Old" treated lumber has been found to leach very insignificant amounts of toxic chemicals into the soil and none have been found to accumulate to any degree in plant tissues. "New" treated lumber is pretty much harmless. Lead-based paint was banned in the US in 1977 and then after much discussion and avoidance of it by most homeowners and paint manufacturers. I doubt you have much to be concerned about but you could always send soil samples in for testing of hazardous chemicals.

The primary way you, or a family member, would be exposed to heavy metals in that soil would be if you ate some. Any plants you grow in that soil will not pick up those heavy metals, but you would not want anyone to eat root crops from that soil without first washing them really well.

The old CCA pressure treated lumber was banned because it was found that as it aged Arsenic was leached out and that would get on people, especially children's, hands or other body parts and could be ingested when those hands were licked.

Good personal hygiene, after working in the garden will do a lot to limit your exposure to any problems from that soil.

kimmq is kimmsr

Just because lead paint was banned for residential use in 1978 does not mean you have none next to your house. In fact your situation is ripe for having some elevated level of lead within a couple feet of the house just from erosion of the original layers of paint before non-leaded paint was put on top. And if it was ever scraped or sandblasted without good containment, it would be higher than that.

You can get a lead test pretty cheaply. Call up your county Ag Extension office and/or health department and ask about where to get that done. You would collect soil from the top few inches from several spots equally and mix it up well.

Or, you could just do as kimmq suggests: wash veggies well that actually get soil on them to avoid passive ingestion of small amounts of soil.

BTW adults are a lot less susceptible to Pb than children.

Older treated lumber is going to have Cr and As. You can test for these as well if you are concerned. I would defer to Gardengal's advice here though, she's usually spot on.