Critical evaluation of historical occupational aerosol exposure records: applications to nickel and lead.

Published or unpublished data sets on individual occupational exposure situations are frequently combined and used for some wider purpose, either hazard evaluation or standards setting. This paper describes a model by which such individual data sets for occupational aerosol exposures might be evaluated in terms of their usefulness in this regard. For workplace aerosols, the model is centered around the particle size-selective framework for aerosol exposure assessment that has emerged in recent years as a rational basis for standards setting. In this paper, reported occupational exposures to airborne nickel and lead are used as examples. In a comprehensive review, 106 published peer-reviewed sources of potentially useful exposure data were found for nickel and 111 similar reports for lead. In addition, for lead 116 unpublished reports in the form of hazard evaluation reports from the US National Institute for Occupational Safety and Health were also examined. For both nickel and lead, a wide range of industry sectors was represented, and the data sets cover the period from 1930 to the present day. It was found that such published data sets are highly inconsistent in terms of the criteria by which the data were obtained, notably for the paucity of essential details of the methods that were used. In contrast, for the lead exposures, the unpublished government reports are more consistent, since they usually followed recognized exposure assessment standards. However, the latter may be misleading because they may have tended to represent high exposure situations. The evaluation model described in this paper provides not only a basis for the evaluation of historical exposure data but also guidelines for new exposure assessment to be carried out in the future. Meanwhile, although many of the historical exposure data sets were found to be generally quite weak in terms of their immediate usefulness, attention is drawn to some of their statistical properties that might allow their enhancement for the purposes of hazard evaluation and retrospective exposure assessment exercises.