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Release and transformation of ZnO nanoparticles used in outdoor surface coatings for UV protection
Citation:
Clar, J., W. Platten III, E. Baumann, A. Remsen, Stephen M. Harmon, K. Rogers, T. Thomas, J. Matheson, AND Todd P. Luxton. Release and transformation of ZnO nanoparticles used in outdoor surface coatings for UV protection. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 670:78-86, (2019). https://doi.org/10.1016/j.scitotenv.2019.03.189
Impact/Purpose:
Current wood treatment and surface applications employing nanoscale ZnO (UV protection) and Cu2CO3(OH)2 (antimicrobial) reflect uses with very high exposure potential and provide a unique opportunity to integrate ORD?s scientific ?niche? in the areas of exposure, health and ecological effects, and modeling. This novel product-application-based research will examine nanoscale ZnO, Cu2CO3(OH)2 formulations and their transformed products employed in wood treatment\coating by determining their release, exposure, fate, and transformation as well as their health and ecological effects. Research will critically inform the engineered nanomaterial (ENM) decision tree product and provide information to develop integrated adverse exposure pathways (AEPs) to adverse outcome pathways (AOPs) associated with current wood treatment and surface applications employing ENM ZnO and Cu2CO3(OH)2 commercial products. Unique aspects of this research include the use of commercial nanoscale products, characterization ENM release and transformation associated with a high exposure application, and assessing the effects associated with exposure to mixtures of ZnO, Cu2CO3(OH)2 ENMs and their transformed products. Research findings will inform: i) regulatory uncertainties associated with exposure and effect risks associated with ENM employed in antimicrobial and surface applications with high exposure potential; and ii) newly initiated European Commission LIFE project NanoMONITOR effort that will inform ENM risk assessment under REACH.
Description:
A major area of growth for “nano-enabled” products has been the addition of nanoparticles (NPs) to surface coatings including paints, stains and sealants. Zinc oxide (ZnO) NPs, long used in sunscreens and sunblocks, have found growing use in surface coating formulations to increase their UV resistance, especially on outdoor products. In this work, ZnO NPs, marketed as an additive to paints and stains, were dispersed in Milli-Q water and a commercial deck stain. Resulting solutions were applied to either Micronized-Copper Azole (MCA) pressure treated lumber or a commercially available composite decking. A portion of coated surfaces were placed outdoors to undergo environmental weathering, while the remaining samples were stored indoors to function as experimental controls. Weathered and control treatments were subsequently sampled periodically for 6 months using a simulated dermal contact method developed by the Consumer Product Safety Commission (CPSC). The release of ZnO NPs, and their associated degradation products, was determined through sequential filtration, atomic spectroscopy, X-Ray Absorption Fine Structure Spectroscopy, and electron microscopy. Across all treatments, the percentage of applied zinc released through simulated dermal contact did not exceed 4%, although transformation and release of zinc was highly dependent on dispersion medium. For MCA samples weathered outdoors, water-based applications released significantly more zinc than stain-based, 180 ± 28, and 65 ± 9 mg/m2 respectively. Moreover, results indicate that the number of contact events drives material release.
URLs/Downloads:
DOI: Release and transformation of ZnO nanoparticles used in outdoor surface coatings for UV protection
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