Evaluation of Decision Rules in a Tiered Assessment of Inhalation Exposure to Nanomaterials.

Tiered or stepwise approaches to assess occupational exposure to nano-objects, and their agglomerates and aggregates have been proposed, which require decision rules (DRs) to move to a next tier, or terminate the assessment. In a desk study the performance of a number of DRs based on the evaluation of results from direct reading instruments was investigated by both statistical simulations and the application of the DRs to real workplace data sets. A statistical model that accounts for autocorrelation patterns in time-series, i.e. autoregressive integrated moving average (ARIMA), was used as 'gold' standard. The simulations showed that none of the proposed DRs covered the entire range of simulated scenarios with respect to the ARIMA model parameters, however, a combined DR showed a slightly better agreement. Application of the DRs to real workplace datasets (n = 117) revealed sensitivity up to 0.72, whereas the lowest observed specificity was 0.95. The selection of the most appropriate DR is very much dependent on the consequences of the decision, i.e. ruling in or ruling out of scenarios for further evaluation. Since a basic assessment may also comprise of other type of measurements and information, an evaluation logic was proposed which embeds the DRs, but furthermore supports decision making in view of a tiered-approach exposure assessment.

A structured observational method to assess dermal exposure to manufactured nanoparticles DREAM as an initial assessment tool.

Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.