We're actually not sure if this is a bug or intended...
Although going into map mode allows pollution to display on the fullsized map, there does not appear to be any way to enable pollution on the minimap in the new UI.
[0.15.1] Minimap will not display pollution
Re: [0.15.1] Minimap will not display pollution
Hi, thanks for the report. Pollution is not displayed on minimap anymore. We forgot to mention it in changelog.