A medical term that refers to the excessive growth of fibrous tissue in some part of the body. Many types of fibroses are known, including a number that affect the respiratory system. A number of these respiratory fibroses, including such conditions as black lung disease, silicosis, asbestosis, berylliosis, and byssinosis, are caused by environmental factors. A fibrosis develops when a person inhales very tiny solid particles or liquid droplets over many years or decades. Part of the body's reaction to these foreign particles is to enmesh them in fibrous tissue. The disease name usually suggests the agent that causes the disease. Silicosis, for example, is caused by the inhalation of silica, tiny sand-like particles. Occupational sources of silicosis include rock mining, quarrying, stone cutting, and sandblasting. Berylliosis is caused by the inhalation of beryllium particles over a period of time, and byssinosis (from byssos, the Greek word for flax)is found among textile workers who inhale flax, cotton or hemp fibers.