Pulmonary fibrosis causes scar tissue to form in the lungs’ air sacs, making it more difficult for the lungs to deliver oxygen to the bloodstream. A type of interstitial lung disease, it can have several different causes, from environmental pollutants and medications to medical treatments and conditions. Sometimes, though, there is no known cause. In those cases, it’s known as “idiopathic pulmonary fibrosis.” Whatever the contributing risk factor, the symptoms of pulmonary fibrosis may at first be mild. But over…