Good morning, I have my physical examination which includes chest x-rays, when I got the result it stated there that I have residual fibrosis in the lower left lung, I am not an occasional smoker and a drinker, also I have no history of having TB, last three months ago when I was in abroad I my have physical examination regarding chest x-ray the result shows clear and in good health, can I know what cause this? And it will be permanent?