Ask HN: What happened to the air quality improvements from Covid-19 lockdowns?

People weren't commuting to the office or going to restaurants and gyms, so there were fewer cars on the road [0].

Fewer of [anything that exudes toxins] will result in increased air quality; cars, factories, even humans to an extent.

Now that more people are going back to the office, restaurants, and/or gyms, the air quality has "increased" back to the level it once was. [1]

[0] https://www.scientificamerican.com/article/the-pandemic-show...

[1] https://www.esa.int/Applications/Observing_the_Earth/Coperni...

I don't have specific numbers for you, but https://maps.s5p-pal.com/ has historical maps of NO2 pollution going back to 2018.