The range of pollutants that may be present at contaminated sites are highly variable, obviously, depending on what chemicals, what pollutants, what exposure scenarios may be present and whether or not they may have disproportionately impacted people on the sites, like toddlers at playgrounds or pregnant people in the environment.
It's difficult to answer that in a very succinct answer, but I would say that many of these chemicals can lead to increased risks of cancer over time. That's why it's important that the health-based input that's provided underpins the actions that custodians are taking on these contaminated sites.