Personal Sampling for Inhalable Aerosol Exposures of Carbon Black Manufacturing Industry Workers

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Abstract
The study was concerned with the measurement of inhalable aerosol exposures in the carbon black production industry. The primary goal of the study was to determine the extent to which inhalable aerosol exposure, as measured by the Institute of Occupational Medicine (IOM) personal inhalable sampling head, compared to "total" aerosol exposure, as measured by traditional methodology. A secondary objective was the evaluation of another inhalable aerosol sampler for carbon black aerosol measurement. In addition, an exploratory evaluation of the applicability of the National Institute for Occupational Safety and Health (NIOSH) analytical method (Method 5040) for the determination of carbon black, measured as elemental carbon, was conducted. A field study was carried out in a number of North American carbon black production plants using three samplers: the 2 Lpm IOM sampler as a reference sampler for the inhalable fraction, the 2 Lpm closed-face 37-mm plastic cassette that has been used for many years for total aerosol, and the 3.5 Lpm GSP sampler that has recently been identified by some as a possible candidate for inhalable aerosol. No such studies have previously been reported for the carbon black industry. Further, there have been no reports of the GSP performance in direct comparison to a reference instrument like the IOM sampler. The results showed that inhalable aerosol exposures for workers in carbon black production and packing areas were higher than the corresponding total aerosol exposures by a factor of nearly three, implying the presence of significantly coarser aerosol than previously thought based simply on knowledge of the carbon black production process. The fact that the aerosols collected in portions of the process comprised high proportions of non-elemental carbon particulate was thought likely to be responsible, underlining the need to consider whether gravimetric assessment for such exposure is the most appropriate metric. In addition, and somewhat surprisingly, the GSP sampler emerged clearly as a good alternative to the IOM sampler for collecting inhalable aerosol in carbon black industry workplaces like those studied (although this conclusion cannot yet be extended to other workplaces).