There are many different things that can cause lung disease. In most cases, disease of the lungs is caused by prolonged smoking. The risk of contracting this condition varies depending on how long a person has smoked, if they've ever quit and if they're still currently a heavy smoker. For this reason, it is important to work diligently to quit smoking as soon as possible. The sooner that you quit smoking, the healthier your lungs will be and the fewer problems you'll experience over time.
Even if you've never been a smoker, you could still develop lung disease at some point in your life. The condition could be a result of environmental factors, like smoke, coal or exposure to asbestos. Workers who regularly did jobs with or around these materials may eventually develop lung-related problems later in life.
Some cases of lung disease, such as asthma, can affect people of all ages, even children. Likewise, someone who was around secondhand smoke a lot when they were a child or teenager may develop lung issues when they become an adult. Some people are simply more prone to developing the condition than others, so genetics also plays a role.