HUMAN RESPONSE TO CONTROLLED LEVELS OF INERT DUST

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Abstract
Nasal mucous flow, airway resistance and subjective response were studied in 16 young healthy subjects during 5 h exposures to 2, 10 and 25 mg of inert dust/m3 in an environmental chamber. The dust was a fully polymerized plastic dust containing C black. The number of these particles in room air, expressed as a per cent of the total number of particles was 36, 41, 14, 7 and 2, respectively, for the aerodynamic size ranges .ltoreq. 1.8, 1.9-5.3, 5.4-8.9, 9.0-12.4 and .gtoreq. 12.5 .mu.m. No significant changes in nasal mucociliary clearance rate or nasal resistance were observed. At all dust concentrations there was a decrease in 1 s forced expiratory volume, but not in the forced vital capacity or the forced expiratory flow during the middle half of the forced vital capacity. The nasal penetration fraction of particles was approximately 55% for the smallest particles and 20% for the largest particles. Discomfort was proportional to the concentration of dust but lagged almost 2 h behind the changes in dust concentration. The discomfort was never excessive; the main complaints were dryness in the nose and pharynx.