A conceptual model for assessment of inhalation exposure to manufactured nanoparticles
Derk H. Brouwer, TNO Quality of Life, The Netherlands
Since workplace air measurements of manufactured nanoparticles are relatively expensive to conduct, models can be helpful for a first tier assessment of exposure. A conceptual model was developed to give a framework for such models. The basis for the model is an analysis of the fate and underlying mechanisms of nanoparticles emitted by a source during transport to a receptor. Four source domains are distinguished; i.e., production, handling of bulk product, spraying, fracturing and abrasion.
These domains represent different generation mechanisms that determine particle emission characteristics; e.g. emission rate, particle size distribution and source location. During transport, homogeneous coagulation, scavenging and surface deposition will determine the fate of the particles and cause changes in both particle size distributions and number concentrations. The degree of impact of these processes will be determined by a variety of factors including the concentration and size mode of the emitted nanoparticles and background aerosols, source to receptor-distance, and ventilation characteristics. In the second part of the presentation the focus will be on to what extent the conceptual model could be fit into an existing mechanistic predictive model for ‘conventional’ exposures. The model should be seen as a framework for characterization of exposure to (manufactured) nanoparticles and future exposure modeling.