I wasn't comparing much of anything for ambulance response times because, as I said, I couldn't find concrete data on it. I'm not sure what rural area you're referring to but the anecdote from the south of Spain was in a city with over half a million people.
Anyway, as for air quality, a population adjusted measure of exposure: https://ourworldindata.org/grapher/PM25-air-pollution
Choosing (small) areas and some samples doesn't make a lot of sense, though. Comparing a small city with a county hospital to some rural area and saying "see, there are areas here were medical services are much closer" is obvious and somewhat useless. You'll want to compare the average or median accessibility, not tiny sub-samples.