Welcome to the forum.....
I think many of us would all like to live in a less polluted community, but for whatever reasons, we live where we do and the reality is that we cannot (realistically) live in a bubble or perfect atmosphere. Having said that, just like we humans, our companion birds may or may not get sick, if we do, we go see a doctor & if our feathered friends do, we take them to a veterinarian, but realistically, if we do the best we can in the husbandry of our charges, they should enjoy good lives.....
If you were to read through the various threads of the forum, you'll find that there are a number of members who walk their birds with harnesses and there are a number of members who walk their birds with bird packs and/or small travel cages....and maybe a few that aren't so small travel cages...the members enjoy it & I'm sure their birds enjoy it.....
You say you might be with your bird 24/7, just be sure to establish boundaries & address screaming/noise early on, lest you run into problems with tour neighbors/landlord.....they haven't yet designed the perfect bird...the one that comes out of the box as non-biters, all cuddly, quiet & nice...they'll always be a work-in-progress.....although we all do it, lavishing a lot of attention & a lot of interaction on a new feathered friend can cause separation problems when job demands require more of our time or work shifts change.....
Others will probably pop in here to give you more tips/insights.....Good luck.....