Size range of dust, which is regarded as health hazard: September 2011
Ans. C: 0.5 to 3 microns Dust paicle within the range of 0.5-3 micron, is a health hazard producing, after a variable exposure, a lung disease known as pneumoconiosis Common Occupational Lung Diseases Asbestosis, caused by exposure to asbestos paicles. Often found among people who worked in shipyards, asbestos mines, and factories that refined or used asbestos to manufacture products. Black lung (Coalworker's pneumoconiosis) which affects coal workers Chronic Beryllium disease (CBD), which affects workers in a variety of metallurgical occupations Byssinosis (brown lung disease), often occurs in cotton and textile workers when bacteria released from cotton or other materials is inhaled and grows with the lungs. This is often associated with poor ventilation systems. Hypersensitivity pneumonitis, this can affect people who work in office buildings whose air-conditioning systems are contaminated by ceain fungi and bacteria. Occupational asthma, can affect people who work with a variety of materials. This includes animals (dander), carbamates (urethanes), dyes, epoxy resins and enzymes used in detergent, leather goods, latex, and automotive paints Silicosis often developed by people who worked with clay, sand and stone dust including miners, stone cutters and sandblasters. How Diseases Develop Pneumoconiosis is the classification of diseases that develop as the result of occupational exposure to dust. Occupational lung diseases develop based on the size and type of paicles inhaled and where the inhaled paicle end up. Larger paicles are more likely to get stuck in the nose and larger airways but smaller paicles can reach the alveoli where they can potentially be absorbed into the bloodstream. When inhaled paicles come in contact with the wall of the airway they do not become airborne again. This is called deposition and can occur in one of four ways: - Sedimentation: When gravity causes paicles to settle, tends to occur in larger airways. - Ineial impaction: Often occurs in the nose and larger airways, it happens when an airway changes direction - Interception: This form of deposition occurs with fibrous dust paicles (including asbestos fibers) or any other irregular shaped paicles. Due to their shape they often avoid deposition by sedimentation or ineial impaction but are deposited in the walls of the bronchioles which are lined with epithelial cells. - Diffusion: Behavior of small aerosol paicles which encounter and are affected by molecules of air. During regular breathing (at rest) about 10% of compact paicles of 0.5 to 1 micron diameter are deposited in the alveoli with the vast majority being exhaled.
0.1 to 0.3 microns
0.3 to 0.5 microns
0.5 to 3 microns
3 to 5 microns