Evaluation of Quantitative Exposure Assessment Method for Nanomaterials in Mixed Dust Environments: Application in Tire Manufacturing Facilities

Abstract

Current recommendations for nanomaterial-specific exposure assessment require adaptation in order to be applied to complicated manufacturing settings, where a variety of particle types may contribute to the potential exposure. The purpose of this work was to evaluate a method that would allow for exposure assessment of nanostructured materials by chemical composition and size in a mixed dust setting, using carbon black (CB) and amorphous silica (AS) from tire manufacturing as an example. This method combined air sampling with a low pressure cascade impactor with analysis of elemental composition by size to quantitatively assess potential exposures in the workplace. This method was first pilot-tested in one tire manufacturing facility; air samples were collected with a Dekati Low Pressure Impactor (DLPI) during mixing where either CB or AS were used as the primary filler. Air samples were analyzed via scanning transmission electron microscopy (STEM) coupled with energy dispersive spectroscopy (EDS) to identify what fraction of particles were CB, AS, or 'other'. From this pilot study, it was determined that ~95% of all nanoscale particles were identified as CB or AS. Subsequent samples were collected with the Dekati Electrical Low Pressure Impactor (ELPI) at two tire manufacturing facilities and analyzed using the same methodology to quantify exposure to these materials. This analysis confirmed that CB and AS were the predominant nanoscale particle types in the mixing area at both facilities. Air concentrations of CB and AS ranged from ~8900 to 77600 and 400 to 22200 particles cm(-3), respectively. This method offers the potential to provide quantitative estimates of worker exposure to nanoparticles of specific materials in a mixed dust environment. With pending development of occupational exposure limits for nanomaterials, this methodology will allow occupational health and safety practitioners to estimate worker exposures to specific materials, even in scenarios where many particle types are present.

Nano-Scaled Particles and Fibres Occupational Exposure Assessment: An Integrated Approach from Air Sampling to Skin and Surface Contamination

“…The ELPI technique has been used by Kreider et al [28] in a real workplace environment, successfully managing to assess carbon black and amorphous silica in a tire manufacturing facility, confirming the presence of such NPs in the workplace. The method has been found useful in providing quantitative estimates of worker's exposure to NPs.…”

Nanomaterials: certain aspects of application, risk assessment and risk communication

“…The increased application of nanomaterials (NMs) in production (Bekker et al 2013 ; Kreider et al 2015 ) and construction (Hanus and Harris 2013 ; Hincapie et al 2015 ), as well as in a wide range of nano-enabled consumer and medical products (Vance et al 2015 ) has resulted in an enhanced exposure of humans and the environment. Besides the ingestion of NMs with food (Szakal et al 2014 ), direct dermal contact (Gulson et al 2015 ) and inhalation (Donaldson and Seaton 2012 ) represent scenarios that humans may encounter.…”