Wildfire induced release of Cr nanoparticles from Tire Crumb Rubber.

Wildfire activity at the Wildland-Urban Interface is increasingly burning structures and anthropogenic materials. It is documented that wildfire alters the form and increases mobility of trace metals in natural environments, yet little is known about their fate in burned anthropogenic materials. We use single particle inductively coupled plasma mass spectrometry (spICP-MS), to examine how burning during a wildfire impacted the elemental composition, and size of metal containing nanoparticles (< 100 nm) in Tire Crumb Rubber (TCR), an end-of-life tire byproduct used in playgrounds, gardens, and urban areas. We show that burned TCR from a playground is a source of potentially toxic metal containing nanoparticles (NPs), including Cr, Ni, Zn, Pb, and Cu. Metal-containing NPs from burned TCR were significantly more abundant than unburned, suggesting greater environmental mobility. We report a unique population of Cr rich NPs resulting from burning, and which were not observed for other metals. These NPs showed increased Cr mass per particle and over two orders of magnitude increase in number. Nanoparticles are a vector for respiratory exposure to trace metals, with their small size increasing penetration into the lung, underpinning the importance of studying NP release from anthropogenic materials which are widely used in the built environment.