Life-Cycle Transformations of Metal and Metal-Oxide Nanoparticles from Commercial Products

Abstract

The environmental fate and effects of engineered nanomaterials have become a topic of interest to researchers due to their increased incorporation within consumer products. Current research into the effects of nanoparticles towards the environment focuses almost entirely on using the pristine form of the nanoparticles for testing. We examine the chemical and physical transformations of nanoparticles in commercial products by modeling typical use scenarios that could occur throughout the product lifecycle. Nanomaterial-containing commercial products were put through conditions mimicking the lifecycle from product incorporation to leaching into the wastewater collection stream. TEM, EDS, XPS and ICP-MS was used to examine the morphological and compositional effects of the product lifecycle on the nanoparticles. AgNPs have seen widespread use in consumer products due to their exceptional antimicrobial properties. We studied the transformation of AgNPs from the production of AgNPs-laden textiles., through day-to-day use scenarios including the exposure to sweat due to the market for the AgNP-containing sports clothing, as well as laundering, which would expose the nanoparticles to detergent and bleach, and finally leaching into the wastewater collection system. Exposure to these weathering conditions showed the aggregation and agglomeration of AgNPs as well as transformation into AgCl and Ag2S. ZnONPs have been widely used for their antimicrobial properties and more recently as a UV blocker. The lifecycle of ZnONPs was tested within medicated baby powder, athletic socks, sunscreen, and UV protective textiles as well as in the pristine nanoparticle form. ZnONPs were observed to dissolve into solution, a process accelerated by an acidic environment. Transformation to ZnCl2 and ZnS salts were also observed. CeO2NPs have been gaining attention in recent years due to their remarkable catalytic antioxidant properties. CeO2NPs have not been widely used in consumer products. Due to the many benefits of CeO2NPs, it had been suggested to be used as a UV blocker by various sources. Assuming the inevitable use of CeO2 nanoparticles in sunscreens, we have impregnated current consumer sunscreens with CeO2NPs and analyzed the chemical and physical transformation through the lifecycle of the product. The CeO2NPs were observed to agglomerate and chemically associate with chlorine and sulfur.