The definition of pneumoconiosis is an inhalation lesion caused by foreign nonliving material in the widest sense, but is usually restricted to inorganic matter. Inhalation causes a tissue reaction, which can be any kind of pneumonia, granulomatosis, or similar. Primarily, when thinking about pneumoconiosis, silicosis and asbestosis will immediately come into one’s mind; however, there are many more agents causing pulmonary diseases. As in many other diseases, in all kinds of pneumoconiosis there is a dose-effect relationship: This means there is a threshold dose required to induce disease (amount of a mineral), and the duration of exposure (cumulative dosis). In addition, the dimension of the particles is important too: particles larger than 10 μm are deposited in the larger airways, and particles below 2–5 μm will reach the alveolar periphery. But, there is another factor called the aerodynamic diameter: particles are within the airstream and will orient themselves along the axis of the airflow; therefore, asbestos fibers, although 100–200 μm in length, are less than 5 μm thick, which means they are longitudinally oriented within the airstream and might reach small bronchioles before being trapped at bifurcations. Another quality of inhaled mineral dust is durability: some metals are easily dissolved in extracellular fluids (e.g., cobalt) and can be absorbed and removed by macrophages. Other minerals such as quartz and asbestos fibers are long-lasting and resist degradation by macrophages for months. Finally, also chemical composition plays a role: highly toxic compounds will cause acute injury to the lung (e.g., cobalt), whereas other minerals cause injury only in huge quantities (e.g., tungsten).