It's mostly the emissions from diesel generators which many DCs use as it's far too expensive to ever shut them down. Often diesel generators are used to lighten the load on a power grid as well, so many DCs will run generators 24/7.

That source of power, since our grid is so outdated and struggles with the weight of these power-hogs, EVs as well as increased usage of AC during the summers create some dangerous conditions.

There is the risk of heavy metals getting into the water supply as the copper degrades but that will only be a problem down the line, that's prescient but not yet realized.

> I'm willing to bet that a datacenter creates a fraction of the pollution of a similarly sized industrial facility such as a chemical plant, refinery, smelter, or steel mill.

I agree; however I would not want a DC or a refinery, smelter or steel mill anywhere near my town. We have industrial districting for that reason, and because a lot of DC projects want to be put next to lakes and water sources, this causes issues for the residents.