The International Organization for Standardization (ISO) has published standard ISO/TS 21361:2019, “Nanotechnologies — Method to quantify air concentrations of carbon black and amorphous silica in the nanoparticle size range in a mixed dust manufacturing environment.”  The standard provides guidelines to quantify and identify particles of carbon black and/or amorphous silica in air samples collected in a mixed dust industrial manufacturing environment.  The guidelines describe air sample collection and the characterization of the particles in the air samples by both particle size and elemental composition.  ISO notes that although the technique described is for carbon black and amorphous silica, the technique can be applied to the measurement of other particle types, provided they are in the size range of six nanometers (nm) to 2.5 micrometers (µm) and can be observed by Transmission Electron Microscopy (TEM)/Scanning Electron Microscopy (SEM) and chemically characterized by Energy Dispersive Spectrometry (EDS).  ISO states that at this time, the methodology represents one of the methods available to quantify chemical‐specific exposures to nanoparticles by size with this degree of sensitivity.  Many of the other existing methods that can speciate and quantify chemical exposure in this size range are mass‐based, and thus are limited by mass‐based detection limits that are high when compared to the mass of particles in this size range.  Furthermore, according to ISO, while other sampling methods may be amenable to the techniques described in the standard, none have been evaluated or validated for this purpose.  ISO suggests that the methodology could be implemented as a higher tier step in an occupational exposure assessment sampling strategy for nanomaterials, particularly in the event that hot spots for exposure are identified using other methods and there is an interest in understanding the nature of the exposure.  Results from the analysis can be used to compare to health benchmarks, as they become available, to understand potential health risk of workers.  In addition, it could be useful in selecting appropriate personal protective equipment (PPE) at a very early stage of the manufacturing process, when required.

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