<prompt> The dangerous particle size causing pneumoconiosis varies from:100-150 um50-100 um10-50 um1-5 um  <response>: Ans. d 1-5 umRef: Robbins 9thpg 689; 8thpg 697For pneumoconiosis, the most dangerous particles are from 1 to 5 um in diameter, because particles of this size may reach the terminal small airways and air sacs and settle in their linings. 