is this one of those situations where it's probably just as bad or worse around the world but they only tested in Europe? or is there something explicitly wrong with just that continent? I'd imagine air in china and the USA (especially in cities) to be just as bad or worse
They only tested Europe as that is who funded the research.
The data was compiled by academics at Utrecht University in the Netherlands and the Swiss Tropical and Public Health Institute as part of the EU-funded Expanse project.