Measurement of coarse aerosols in workplaces. A review.

Coarse aerosol fractions in workplaces are sampled if it is felt that particles of all sizes may pose a risk to health. Although the so-called 'total' aerosol has been widely used to refer to the relevant coarse fraction, practical measurement has been very dependent on the actual sampling instrument used. This in turn has led to great uncertainty about what was being measured. In the 1980s, the concept of inhalability was proposed, based on the aerosol particle size fraction that enters the human head through the nose and/or mouth during breathing. Now there is substantial agreement by most of the world's major criteria-setting bodies on a quantitative definition taking the form of a single curve describing the probability of inhalation as a function of particle aerodynamic diameter. This definition now forms a truly health-related 'yardstick' against which to assess the performances of practical sampling devices. In turn, more and more countries are beginning to adopt the new criterion for health-related aerosol measurement in their standards, replacing the old 'total' aerosol concept. Experiments in wind tunnels to investigate the performances of previous samplers for 'total' aerosol show that most of them do not satisfactorily match the new inhalability criterion. A small number of samplers designed specifically for the inhalable fraction have been proposed and are available commercially. They include samplers for both static (or area) and personal sampling.