Respirable dust, responsible for pneumoconiosis, has a size limit of:: (A) <1 micron, (B) <5 micron, (C) <10 micron, (D) <100 micron
Answer is B. Pneumoconiosis occur due to occupational exposure to dust. Paicles size 0.5 to 3.0 microns are the most dangerous (as a health hazard causing pneumoconiosis), as they reach the interior of lungs with ease. Paicles size and behaviour: Paicle size Behaviour >10 microns Settle down by gravity <10 microns Remain suspended in air 5-10 microns Arrested in upper respiratory tract 3-5 microns Deposited in mid respiratory tract 1-3 microns Enter alveoli and settle there (cause pneumoconiosis) <1 more Brownian movement Ref: Park 25th edition Pgno: 843