I've needed my inhaler way less since the ULEZ came in.
Visiting London used to mean blowing your nose to black snot for a week afterwards, these days living in London it's pretty good.
I've not lived in London for more than a decade. I always thought the black snot was from the Tube. Is it not?
Anecdotal, but similar situation here for me (I don't need an inhaler, but visiting London around 2015 meant blowing my nose to black snot for a week, and then back in 2024 it was completely fine)!
More anecdata: I've been using my inhaler more since moving to a city with worse air quality than my previous location.
People don't fire their chimneys or have garden bonfires much any more, either.
ULEZ massively reduced the amount of NO2, which is a trigger for asthma. It also seems to have reduced the hospital admissions for heart related emergencies.
Sources:
https://www.bbc.com/news/articles/c75q9d2pqyeo https://www.theguardian.com/environment/2026/jun/12/emergenc...