It's plausible, but I think the experience thus far is any dust in the lungs is a health risk. Asbestos will not be soon forgotten.

I'd be more worried about testing phosphogypsum's mechanical properties before anyone starts testing the radioactive ones. And danger relative to tyre rubber; although that has probably already been studied somewhere since it is an obvious thing to check.

I expect it to — roads wear down and need resurfacing often enough, and that stuff has to go somewhere, either into the air as dust or dissolved in the rain and run off into the soil.