Lung silicosis. Light micrograph of a section through a lung with silicosis, a type of pneumoconiosis caused by exposure to silica dusts. The lung tissue has become fibrous and contains many macrophages (immune system cells) that have engulfed particles of carbon (carbon) in an effort to clear the dust from the lungs. Symptoms include breathlessness and a chronic cough. There is no cure for silicosis, treatment is aimed at reducing the symptoms. Silicosis is most prevalent in people working in the mining and quarrying industries.