title: Outdoor urban nanomaterials: The emergence of a new, integrated, and critical field of study.
abstract: Engineered nanomaterials (ENMs) are currently widely incorporated in the outdoor urban environmental fabric and numerous new applications and products containing ENMs are expected in the future. As has been shown repeatedly, products containing ENMs have the potential, at some point in their lifetime, to release ENMs into their surrounding environment. However, the expanding body in environmental nanomaterial research has not yet shifted toward ENMs in the context of the complex outdoor urban environment. This is especially surprising because the world's human populations are on a steady march toward more and more urbanization and technological development, accompanied with increased applications for ENMs in the outdoor urban environment. Our objective for this paper is therefore to review, assess, and provide new information in this emerging field. We provide an overview of nanomaterials (NMs, encompassing both ENMs and incidental nanomaterials, INMs) that are likely to be released in the urban environment from outdoor sources by discussing 1) the applications of ENMs that may lead to release of ENMs in urban areas, 2) the recently published data on the release of ENMs from novel nano-enabled applications in the outdoor urban environment, 3) the available literature on the occurrence of INMs in the atmosphere and within/on dust particles, and 4) the potential pathways and fate of NMs in the outdoor urban environment. This review is then followed by three case studies demonstrating the importance of NMs in the outdoor urban environment. The first and second case studies illustrate the occurrence of NMs in urban dust and stormwater ponds, respectively, whereas the third case study discusses the lessons learned from the release of NMs (e.g. Pt, ph and Rh) from automotive vehicle catalytic convertors. This article ends with a discussion of the research priorities needed to advance this emerging field of "outdoor urban nanomaterials" and to assess the potential risks of NMs in the context of urban environments.
authors.affiliation: Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, University of South Carolina, Columbia, SC 29208, USA. Electronic address: mbaalous@mailbox.sc.edu.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Baalousha
authors.affiliation: Department of Geosciences, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, China; Center for NanoBioEarth, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061-0420, USA. Electronic address: yyang@geo.ecnu.edu.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute for Critical Technology and Applied Science, 410 Kelly Hall, Virginia Tech, Blacksburg, VA 24061-0420, USA.
authors.forename: Marina E
authors.initials: ME
authors.lastname: Vance
authors.affiliation: Biology Department, Duke University, Durham, NC 27708, USA; Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT 59812, USA.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Colman
authors.affiliation: Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, University of South Carolina, Columbia, SC 29208, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: McNeal
authors.affiliation: Center for NanoBioEarth, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061-0420, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.affiliation: Biology Department, Duke University, Durham, NC 27708, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Blaszczak
authors.affiliation: College of Agriculture and Life Sciences, Virginia Tech, Blacksburg, VA 24061-0420, USA.
authors.forename: Meredith
authors.initials: M
authors.lastname: Steele
authors.affiliation: Biology Department, Duke University, Durham, NC 27708, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Bernhardt
authors.affiliation: Center for NanoBioEarth, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061-0420, USA; Geosciences Group, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hochella
mesh_terms: D002947:Cities; D004784:Environmental Monitoring; D004785:Environmental Pollutants; D008420:Manufactured Materials; D049329:Nanostructures
chemical_list: D004785:Environmental Pollutants
keywords: Atmosphere; Engineered nanomaterials; Incidental nanomaterials; Storm water; Surface water; Urban environment