PM2.5 Open Data Portal vs UK Carbon Intensity

The LASS PM2.5 Open Data Portal aggregates readings from Taiwan's low-cost civic air-quality sensor networks (AirBox, LASS, EPA, and others) into freely downloadable JSON snapshots, refreshed continuously with no key required. It also runs a DCF (Data Calibration Framework) service that publishes machine-learning-corrected PM2.5 estimates per monitoring site.

This is the official carbon intensity forecast and outturn API for Great Britain's electricity grid, published by National Grid ESO, giving live and forecast gCO2/kWh figures nationally and regionally. It's a fully open government data feed with no key required.