[zerealshadowban]

I've been using the PurpleAir website (map.purpleair.com) for many years now, mostly out of concern for heavy wildfire pollution and winter inversions vs personal outdoor+athletic activities; one interesting aspect is that you can buy your own sensor and thus join the community of local sensors for increased accuracy of measurements. They let you pick between various international standards and types of pollutants. They seem to have a dense network of sensors in North America, not sure about the rest of the world.