The US has accumulated 83.000 tons in decades. Compare that to the billions of tons CO2 that coal plants blow into the atmosphere.
https://en.wikipedia.org/wiki/Health_effects_of_coal_ash
Though, I agree CO2 is bigger problem. Unless you just bought property in Greenland and wait for it to live up to its name.
The US has accumulated 83.000 tons in decades. Compare that to the billions of tons CO2 that coal plants blow into the atmosphere.