Hi Kate, congratulations on your kak.
Unless you live in a very high pollution area, you probably do not have to worry as much as you might think you do. If there are other birds (wild) that live around you, then you'd probably be safe taking your feathered friend outside for walks and such. If you live in a high pollution area and the air in your house is cleaner than that outside, I would probably keep my bird inside, rather than go out with it.
While we humans do have an obligation to protect an care for animals we choose to keep as pets, we cannot really keep those pets in a biosphere where there is no danger. 20-30 years ago, there was a boy, I believe, in Houston, Texas, whose immune system was all messed up and to keep him safe from infection, he was kept in a plastic bubble in a hospital and finally he convinced the doctors and his parents to let him live a normal life, though it was not a long one. There was a movie made about him & I think it was called the boy in the bubble.....you might want to watch it if you get a chance.
I know someone who lives in New York city that has a bird pak & takes her African grey out almost every day.....there's a lot of automobile pollution in NYC, but her bird is going on 20 this year. I am not saying she is right or wrong, but her bird passes all of its veterinary examinations and I believe the lady takes good care of the grey.....she took the bird from someone who lived in her building who passed away, so as far as I know, the bird has always been in NYC.