My comment isn't talking about CO2. I'm talking about e.g. benzene.
Nuclear waste disposal is concerned/stymied by the possibility that the water table in remote areas where no one lives currently may be moderately contaminated in thousands of years if it fails, and this contamination may last thousands of years.
Whereas we have contaminated the water table in populated areas with benzene and aromatics -- where they will remain contaminated for thousands of tens of thousands of years.
That is, we're trying to prevent theoretical harms in the distant future, and in so doing, we're accepting much larger present harms.