It's fine if some people dig it up and get sick; the lives of a dozen people in 10000 years really aren't that much of our concern. What they're trying to avoid

It's fine if some people dig it up and get sick; the lives of a dozen people in 10000 years really aren't that much of our concern. What they're trying to avoid is people building a city on top of the waste, drilling down for water or other resources, then contaminating a large metropolis.