Advanced filtration and lung deposition models of airborne multi-walled carbon nanotubes for inhalation exposure assessment

Abstract

Precise prediction of airborne carbon nanotube (CNT) filtration and deposition in the lung is of significant importance to find proper control media and to perform exposure assessment to quantify the toxicity for emitted airborne CNTs. We executed a systematic study in order to evaluate the inhalation exposure of inhaled single standing airborne multi-walled carbon nanotubes (MWCNTs) and CNT agglomerates, by assessing their filtration and deposition in the deep lung using calculation models. Filtration, inhalation and deposition were influenced by the agglomeration of the fibrous particles and by the agglomerate mixing state. We revised previous models and developed the models for realistic CNT mixtures in air with a new approach using the mixing states of CNT agglomerates and single standing CNTs. We verified our newly developed filtration model empirically. The calculated lung deposition for the realistic CNT mixtures and CNT agglomerates showed much higher deposition rates than that for single standing CNTs under a variety of flow conditions and in the size range from 76 to 500 nm. The lung deposition and the toxicity are both dependent on the CNT shape and form. Our study illustrates the necessity to consider the CNT morphology and agglomeration status in the evaluation of the airborne CNT health impact. The comparison between the developed lung deposition model and previous empirical study results showed that the particle deposition in the lung is mainly determined during inhalation.