Assessment of particle size distributions of health-relevant aerosol exposures of primary lead smelter workers

Experiments were conducted at a primary lead smelter to investigate the particle size distributions of lead-containing aerosol to which workers were exposed, using personal inhalable dust spectrometers (PIDS) in specific smelter process areas. A total of 46 PIDS samples were evaluated, taken from the ore storage/mill, sinter plant, blast furnace and dress furnace process areas. Continuous particle size distributions were derived from the raw PIDS data employing a recently-developed optimisation routine, enabling determination of the percentages of inhalable, thoracic and respirable aerosol (in terms of lead content) as fractions of total lead aerosol. In addition, the mass ratios thoracic/inhalable and respirable/inhalable were also determined. Although the parameters of the measured particle size distributions ranged widely, some clear trends emerged. Firstly, the aerosols were coarser than had been expected based on measurements of previously reported workplace particle size distributions. This is thought to be due to the fact that the PIDS collects larger particles more efficiently than other instruments which have been used for such measurements. Secondly, there were significant differences in particle size distribution between process areas, in particular that the aerosol in the blast furnace area was generally finer than in the sinter plant. Such results may be used to support the results of workplace studies (reported elsewhere) into the differences between exposures to inhalable and 'total' aerosol as measured using different sampling instruments, especially when they are used together with knowledge of the physical processes governing the performances of such instruments.