Anything that resulted in inflammation can cause scarring in your lungs. This could be foreign particles from smoke, caustic fumes from chemicals or any number of irritants not the least of which could be severe lung infections.
Your quitting smoking is the best thing you could have done. Your lungs have a great potential for healing. Check my website at www.TheNaturalHealthPlace.com for breathing exercises AND do a similar search (on Google, etc.) for additional breathing exercises.
Tai Chi, Yoga and Qi Gong are exceptional exercises to help improve the health of your lungs. With proper diet, exercise and avoidance of smoking you should be able to prevent your mild emphysema getting any worse.
Best of Health,