INTRODUCTION: An increased production and use of @entity505 nanotubes (CNTs) is occurring worldwide. In parallel, a growing concern is emerging on the adverse effects the unintentional inhalation of CNTs can have on @entity1 . There is currently a debate regarding which exposure metrics and measurement strategies are the most relevant to investigate workplace exposures to CNTs. This study investigated workplace CNT emissions using a combination of time-integrated filter sampling for @entity4653 ( @entity4653 ) and direct reading aerosol instruments (DRIs). MATERIAL AND METHODS: Field measurements were performed during small-scale manufacturing of multiwalled @entity505 nanotubes using the arc discharge technique. Measurements with highly time- and size-resolved DRI techniques were carried out both in the emission and background (far-field) zones. Novel classifications and counting criteria were set up for the @entity4653 method. Three classes of CNT-containing particles were defined: type 1: particles with aspect ratio length:width >3:1 (fibrous particles); type 2: particles without fibre characteristics but with high CNT content; and type 3: particles with visible embedded CNTs. RESULTS: Offline sampling using @entity4653 showed emissions of CNT-containing particles in 5 out of 11 work tasks. The particles were classified into the three classes, of which type 1, fibrous CNT particles contributed 37%. The concentration of all CNT-containing particles and the occurrence of the particle classes varied strongly between work tasks. Based on the emission measurements, it was assessed that more than 85% of the exposure originated from open handling of CNT powder during the Sieving, mechanical work-up, and packaging work task. The DRI measurements provided complementary information, which combined with @entity4653 provided information on: (i) the background adjusted emission concentration from each work task in different particle size ranges, (ii) identification of the key procedures in each work task that lead to emission peaks, (iii) identification of emission events that affect the background, thereby leading to far-field exposure risks for workers other than the operator of the work task, and (iv) the fraction of particles emitted from each source that contains CNTs. CONCLUSIONS: There is an urgent need for a standardized/harmonized method for electron microscopy (EM) analysis of CNTs. The @entity4653 method developed in this study can form the basis for such a harmonized protocol for the counting of CNTs. The size-resolved DRI techniques are commonly not specific enough to selective analysis of CNT-containing particles and thus cannot yet replace offline time-integrated filter sampling followed by @entity4653 . A combination of EM and DRI techniques offers the most complete characterization of workplace emissions of CNTs today.

XXXX Nanotube Emissions from Arc Discharge Production: Classification of Particle Types with Electron Microscopy and Comparison with Direct Reading Techniques.

@entity505 :: ('MESH:D002244', 'Chemical') :: ['carbon'] @entity1 :: ('9606', 'Species') :: ['humans'] @entity4653 :: ('MESH:D004401', 'Disease') :: ['SEM', 'scanning electron microscopy']
@entity505 :: (MESH:D002244,Chemical) :: ['Carbon']
