Yes, maybe fewer asthma cases and related deaths over the next decades but not sure if a few months of less pollution are sufficient.

Speaking of pollution:

https://www.theguardian.com/environment/2020/apr/20/air-poll...

Title: Strong correlation between Covid deaths and high air pollution

"Research shows almost 80% of deaths across four countries were in most polluted regions"

Study: 'Assessing nitrogen dioxide (NO2) levels as a contributing factor to coronavirus (COVID-19) fatality'

https://doi.org/10.1016/j.scitotenv.2020.138605

I haven't read those studies but I do hope they controlled for population density...