Size, composition, morphology, and health implications of airborne incidental metal-containing nanoparticles

Abstract

There is great concern regarding the adverse health implications of engineered nanoparticles. However, there are many circumstances where the production of incidental nanoparticles, i.e., nanoparticles unintentionally generated as a side product of some anthropogenic process, is of even greater concern. In this study, metal-based incidental nanoparticles were measured in two occupational settings: a machining center and a foundry. On-site characterization of substrate-deposited incidental nanoparticles using a field-portable X-ray fluorescence provided some insights into the chemical characteristics of these metal-containing particles. The same substrates were then used to carry out further off-site analysis including single-particle analysis using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Between the two sites, there were similarities in the size and composition of the incidental nanoparticles as well as in the agglomeration and coagulation behavior of nanoparticles. In particular, incidental nanoparticles were identified in two forms: submicrometer fractal-like agglomerates from activities such as welding and supermicrometer particles with incidental nanoparticles coagulated to their surface, herein referenced as nanoparticle collectors. These agglomerates will affect deposition and transport inside the respiratory system of the respirable incidental nanoparticles and the corresponding health implications. The studies of incidental nanoparticles generated in occupational settings lay the groundwork on which occupational health and safety protocols should be built.

Keywords:

• Fractal-like agglomerates
• incidental nanoparticles
• NP-collectors
• respiratory deposition curve
• single-particle analysis

Acknowledgments

The ICP-MS analysis was performed in the Environmental Complex Analysis Laboratory on the UC San Diego campus. Irem B. Ustunol also acknowledges Turkey’s Ministry of National Education for her graduate fellowship and support.

Additional information

Funding

This work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of UCSD, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542148). This work utilized the TEM in the University of Iowa Central Microscopy Research Facilities that was purchased with funding from the NIH SIG grant number 1 S10 RR018998-01. This work used equipment borrowed from the University of Iowa Environmental Health Sciences Research Center, NIEHS/NIH P30 ES005605, a center funded by the National Institute of Environmental Health Sciences. Financial support for this work was provided by National Institute for Occupational Safety and Health grants R01 OH010238 and R01 OH010295.