Measurement of electric charge for workplace aerosols

Previous work relating to measurements of electric charges carried by airborne dusts in workplaces is reviewed and the results of our own recent measurements in 13 factories, two quarries and a coal mine are reported. The method of measurement involved using an optical particle counter to determine the proportions of particles in given size ranges penetrating through an ‘electrostatic elutriator’. They show that (a) particle charge levels varied markedly between factories and between different workplaces within the same factory, (b) charge levels in many instances were comparable with those measured for laboratory-generated dusts and (c) charging in all the cases examined was approximately uniformly distributed between positive and negative polarity.

We conclude by discussing the relevance of the workplace results in relation to occupational hygiene, with particular reference to the effects of the electric charge levels on the lung dose of dust received by exposed workers.