Static electrification of workplace aerosols

Electrostatic effects on the pulmonary uptake of dusts are reviewed. Theoretical considerations show that electrostatic enhancement of particle deposition occurs primarily in the alveolar region of the lung for aerodynamically fine particles. For each particle size, there exists a threshold charge below which enhancement is negligible. For a particle of 1 micron diameter, this threshold corresponds to a charge equivalent in magnitude to about 50 electrons. Inhalation studies with human volunteers breathing spherical particles have confirmed the theoretical predictions. Animal inhalation studies using fibrous asbestos (1332214) dusts, however, have shown a relatively greater degree of enhancement for particles of equivalent aerodynamic diameter. The effects of electrostatic charge on sampling and filtration of charged aerosols are discussed. The authors conclude that for isometric dusts in normal circumstances, electric charge effects will not significantly affect lung deposition. For fine fibrous dusts, such as asbestos, electrostatic effects may contribute substantially to lung deposition, and possibly to health risk. Recommendations include giving a high priority to investigating the charge effects on lung deposition of fibrous aerosols and neutralizing test aerosols used in studies involving the exposure of animals and humans to aerosols.