Pneumoconiosis is caused due to inhalation of dust within the size range of -

Paicle size of air contaminants must be considered in pneumoconiosis .Paicles >10-15 microns do not penetrate beyond the nose and throat.Paicles 2.5-10 microns contain crustal elements such as silica,aluminium,and iron.These paicles mostly deposit high in the tracheobronchial tree.Fine -mode fraction include paicles less than 2.5 microns,which are carried to the lower airways and produces pneumoconiosis. Reference:Harrison's medicine-18th edition,page no:2122.