ELECTROSTATIC LUNG DEPOSITION EXPERIMENTS WITH HUMANS AND ANIMALS

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Abstract
The electrostatic charge carried by inhaled aerosol particles enhances their deposition in the airways. Experiments have been performed on volunteers with monodisperse aerosols of diameter 0.3, 0.6 and 1.0 μ m with unipolar charges of each polarity and between 12 and 230 elementary units per particle. A significant deposition increase was found for particle charges exceeding a threshold charge q c , which depends on the particle size but not on the individual volunteer; at the charge concentration used, this increase is due to image forces between wall and particle and depends on the magnitude of charge carried by each individual particle and not on the collective behaviour of the charged particle cloud. The electrostatic deposition efficiency is a function of ( Bq2 ) 1/3 , where B is the mechanical mobility and q is the charge. The inter-subject variability was also investigated together with the influence of the Expiratory Reserve Volume. The electrostatic contribution to deposition was found to decrease with increasing ERV, following the same behaviour as for neutral particles. Since in the size range investigated mechanical deposition takes place only in the alveolar region, enhancement of deposition by electrostatic effects should be alveolar under the experimental conditions described. Several dispersal processes generate aerosols with considerable charge, generally of both polarities. Since in image force deposition each particle interacts individually with the containment, the effect on deposition can be very relevant even if the overall cloud charge is low. This is demonstrated also by the results of deposition experiments both on volunteer human subjects and on animals with aerosols mechanically generated and not sufficiently neutralized.

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