The lungs are different from most of the other organs in your body because their delicate tissues are directly connected to the outside environment. Anything you breathe in can affect your lungs. Germs, tobacco smoke and other harmful substances can cause damage to your airways and threaten the lungs ability to work properly. Your body has a natural defense system designed to protect the lungs. This works very well most of the time to keep out dirt and fight off germs. But there are some important things you can do to reduce your risk of lung disease.