At present, no nanomaterial-specific exposure limits or national/international consensus standards on measurement techniques exist for nanomaterials in the workplace.  However, facilities involved in the production and use of engineered nanomaterials have expressed a desire to learn whether the potential for worker exposure exists. 

In order to address this question, the National Institute for Occupational Safety and Health (NIOSH) established a nanotechnology field research team with the primary goal of visiting facilities and evaluating the potential for release of nanomaterials and worker exposure.  The team identified numerous techniques to measure airborne nanomaterials with respect to particle size, mass, surface area, number concentration, and composition.  However, many of these techniques were found to lack specificity and field portability, as well as being difficult to use and expensive when employed for routine exposure assessment. 

In an attempt to overcome these limitations, NIOSH researchers have developed the nanoparticle emission assessment technique (NEAT) which uses a combination of measurement techniques and instruments to semi-quantitatively evaluate airborne nanomaterial concentrations in the workplace, as described in an article by Methner et al. published recently in the Journal of Occupational and Environmental Hygiene (JOEH).  

The NEAT utilises portable direct-reading instrumentation to detect releases of airborne nanomaterial supplemented by a pair of filter-based air samples (source-specific and personal breathing zone) and subsequent chemical and microscopic analyses for particle identification and chemical speciation.  According to the authors, the use of the filter-based samples are crucial for identification purposes because particle counters are generally insensitive to particle source or composition and make it difficult to differentiate between incidental and process-related nanomaterials using number concentration alone. 

The NEAT has been used by the NIOSH researchers to evaluate potential engineered nanomaterials emissions and potential exposure in 12 facilities, including research and development laboratories, pilot plants, and manufacturing facilities handling carbon nanotubes, carbon nanofibres, fullerenes, carbon nanopearls, metal oxides, electrospun nylon and quantum dots.  According to the researchers, the results obtained from these field studies – described in a second article published in the same issue of JOEH – demonstrate that the NEAT is useful in evaluating emissions and that readily available engineering controls can be applied to minimise nanomaterial emissions.

Source:  Based on materials provided by the Journal of Occupational and Environmental Hygiene.