You are right to be concerned; for a cat, there are a lot of dangers out there - cars, dogs, coyotes, raccoons to name a few. Also, poisons, weed killers, and more.
On the other hand, there is so much excitement and fun outdoors. Both Dr. Rodan and Dr. Miller take their cats out in strollers.
If you can train your cat to walk with a leash and halter (not collar because they get out of them easily), that lets both you and your cat get exercise. A great health idea for both of you!
There are also a variety of kitty enclosures to keep your cat safe in the great outdoors, so that they can watch the birds and other animals, catch the breeze, and yet be safe.
Outdoor enclosures to allow you cat the benefit of the outdoors without the dangers:
The Cat’s DenKittyWalksWild WhiskersGreat hammocks, beds, and toysStill scared? Let your cat stay indoors, with a fun area near the window.
Think Like a Cat with Pam Johnson-Bennett