Particle Size-Selective Sampling in Establishing Threshold Limit Values

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Abstract
The principal deposition and retention sites of inhaled particulate air contaminants are governed by particle aerodynamic size and are critical factors in the nature and severity of resulting injury or disease. Inhaled substances may deposit in the alveolar or gas exchange region, in the thoracic conducting airways or tracheobronchial region, and/or in the oral pharynx or nasopharyngeal region (mouth or nose breathing). Examination of specific air contaminants and specific diseases associated with particular regions of the respiratory tract indicates that size-selective sampling is critical to a meaningful evaluation of the inhalation hazard to the worker. Different particle size distributions of the same contaminant will cause major changes in deposition in different regions of the respiratory tract, markedly changing the relative quantity of material deposited within the region and so determining the probability and nature of the associated disease processes. A procedure for determining particle size-selective threshold limit values is illustrated, using an approach that incorporates earlier attempts of particle size-selective sampling in the workplace, as well as characteristics of inhaled particle collection in the human respiratory tract. Stuart, B. O.; Lioy, P. J.; Phalen, R. F.: Particle size-selective sampling in establishing threshold limit values.