Pollution happens when you don't have enough power in the grid so you will bring either diesel generators or methane turbines to make power.
Also noise is pollution too.
Diesel generators are mostly for emergencies. Natural gas turbines (many of which are or are derived from jumbo jet engines) are for on-prem power generation.
With diesel over $6/gallon now that's probably not too attractive. Natural gas probably more likely, and less polluting at least as far as particulates go. CO2 still created.
Are all new data centers being built with on-site power generation (for regular operations, not just emergency backup)? I'd assume they'd prefer utility power where they could get it.