Browsing by Author "Holder, Amara L."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Characterization of Particle Emissions and Fate of Nanomaterials During Incineration
    Vejerano, Eric P.; Leon, Elena C.; Holder, Amara L.; Marr, Linsey C. (The Royal Society of Chemistry, 2014-01-24)
    As the use of nanotechnology in consumer products continues to grow, it is inevitable that some nanomaterials will end up in the waste stream and will be incinerated. Through laboratory-scale incineration of paper and plastic wastes containing nanomaterials, we assessed their effect on emissions of particulate matter (PM) and the effect of incineration on the nanomaterials themselves. The presence of nanomaterials did not significantly influence the particle number emission factor. The PM size distribution was not affected except at very high mass loadings (10 wt%) of the nanomaterial, in which case the PM shifted toward smaller sizes; such loadings are not expected to be present in many consumer products. Metal oxide nanomaterials reduced emissions of particle-bound polycyclic aromatic hydrocarbons. Most of the nanomaterials that remained in the bottom ash retained their original size and morphology but formed large aggregates. Only small amounts of the nanomaterials (0.023–180 mg g−1 of nanomaterial) partitioned into PM, and the emission factors of nanomaterials from an incinerator equipped with an electrostatic precipitator are expected to be low. However, a sustainable disposal method for nanomaterials in the bottom ash is needed, as a majority of them partitioned into this fraction and may thus end up in landfills upon disposal of the ash.
  • Thumbnail Image
    Nanomaterial Disposal by Incineration
    Holder, Amara L.; Vejerano, Eric P.; Zhou, Xinzhe; Marr, Linsey C. (The Royal Society of Chemistry, 2013-07-11)
    As nanotechnology-based products enter into widespread use, nanomaterials will end up in disposal waste streams that are ultimately discharged to the environment. One possible end-of-life scenario is incineration. This review attempts to ascertain the potential pathways by which nanomaterials may enter incinerator waste streams and the fate of these nanomaterials during the incineration process. Although the literature on incineration of nanomaterials is scarce, results from studies of their behavior at high temperature or in combustion environments for other applications can help predict their fate within an incinerator. Preliminary evidence suggests nanomaterials may catalyze the formation or destruction of combustion by-products. Depending on their composition, nanomaterials may undergo physical and chemical transformations within the incinerator, impacting their partitioning within the incineration system (e.g., bottom ash, fly ash) and the effectiveness of control technology for removing them. These transformations may also drastically affect nanomaterial transport and impacts in the environment. Current regulations on incinerator emissions do not specifically address nanomaterials, but limits on particle and metal emissions may prove somewhat effective at reducing the release of nanomaterials in incinerator effluent. Control technology used to meet these regulations, such as fabric filters, electrostatic precipitators, and wet electrostatic scrubbers, are expected to be at least partially effective at removing nanomaterials from incinerator flue gas.
  • Thumbnail Image
    Toxicity of Particulate Matter from Incineration of Nanowaste
    Vejerano, Eric P.; Ma, Yanjun; Holder, Amara L.; Pruden, Amy; Elankumaran, Subbiah; Marr, Linsey C. (The Royal Society of Chemistry, 2015-01-13)
    Disposal of some nanomaterial-containing waste by incineration and the subsequent formation of particulate matter (PM) along with hazardous combustion by-products are inevitable. The effect of nanomaterials on the toxicity of the PM is unknown. We assessed the oxidative potential (OP) and toxicity of PM resulting from the incineration of pure nanomaterials and of paper and plastic wastes containing Ag, NiO, TiO2, ceria, C60, Fe2O3, or CdSe/ZnS quantum dots (CdSe QD) at mass loadings ranging from 0.1 wt% to 10 wt%. We measured reactive oxygen species (ROS) using the dichlorofluorescein assay, and we also measured consumption of ascorbic acid, dithiothreitol (DTT), glutathione (GSH), or uric acid antioxidants from raw and solvent-extracted PM, denoted “cleaned PM”. We determined cytotoxicity and genotoxicity of PM to A549 human lung epithelial cells with the WST-1 cell viability and histone immunofluorescence assays, respectively. In most cases, the presence of nanomaterials in the waste did not significantly affect the OP of PM; however, PM derived from waste containing Ag, TiO2, and C60 had elevated ROS response in the GSH and DTT assays. The ratio of reduced to oxidized glutathione was significantly higher for cleaned PM compared to raw PM for almost all nanomaterials at almost all concentrations, indicating that combustion by-products adsorbed on raw PM play an important role in determining OP. The presence of nanomaterials did not significantly modify the cytotoxicity or genotoxicity of the PM. Different antioxidants used to assess OP had varying sensitivity towards organic compounds v. metals in PM. The presence of these seven nanomaterials at low concentrations in the waste stream is not expected to exacerbate the hazard posed by PM that is produced by incineration.
  • Thumbnail Image
    Toxicity of Silver Nanoparticles at the Air-Liquid Interface
    Holder, Amara L.; Marr, Linsey C. (Hindawi, 2013-01-01)
    Silver nanoparticles are one of the most prevalent nanomaterials in consumer products. Some of these products are likely to be aerosolized, making silver nanoparticles a high priority for inhalation toxicity assessment. To study the inhalation toxicity of silver nanoparticles, we have exposed cultured lung cells to them at the air-liquid interface. Cells were exposed to suspensions of silver or nickel oxide (positive control) nanoparticles at concentrations of 2.6, 6.6, and 13.2 μg cm⁻² (volume concentrations of 10, 25, and 50 μg ml⁻¹) and to 0.7 μg cm⁻² silver or 2.1 μg cm⁻² nickel oxide aerosol at the air-liquid interface. Unlike a number of in vitro studies employing suspensions of silver nanoparticles, which have shown strong toxic effects, both suspensions and aerosolized nanoparticles caused negligible cytotoxicity and only a mild inflammatory response, in agreement with animal exposures. Additionally, we have eveloped a novel method using a differential mobility analyzer to select aerosolized nanoparticles of a single diameter to assess the size-dependent toxicity of silver nanoparticles.