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Final Progress Reports: University of California-Davis: Remediation and Health Effects

Superfund Research Program

Remediation and Health Effects

Project Leader: Ian M. Kennedy
Grant Number: P42ES004699
Funding Period: 1995-2010

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Final Progress Reports

Year:   2009  2004  1999 

Nanoparticles in the environment that arise from thermal remediation processes and other industrial sources can cause serious health effects by the generation of so-called reactive oxygen species, the hydroxyl radical being one of the most dangerous. Researchers have quantified hydroxyl (OH) generation from a series of individual and mixed dissolved transition metals (Fe, Cu, Cr, V, Zn, Mn, Ni, Cd, Cr, and Pb) in several surrogate lung fluids that mimic conditions in our lungs. Researchers found that:

  1. Fe and Cu are the most reactive metals in generating OH
  2. the generation of OH from Fe and Cu requires ascorbate
  3. other metals are, at most, only minor sources of OH
  4. citrate, glutathione, and uric acid in the surrogate lung fluid alter the reactivity of both Fe and Cu, but in different ways
  5. Fe and Cu together act synergistically to form enhanced amounts of OH compared to the individual metals

Researchers have found a new method for generating nanoparticles of iron and its oxides in a novel flame system. Because these materials are magnetic, researchers can extract the particles from the flame with a magnet, inducing them to form long chains that maintain a very large surface area but with a long dimension that makes them simpler to handle and capture in filters. They have checked the ability of this material to adsorb Arsenic in water (with the Transport, Transformation and Remediation of Contaminants in the Environment: Exposure Assessment in Heterogeneous Environmental Media project) and found it to be quite effective – and much cheaper than commercial iron nanoparticles for water treatment. Its geometric properties make it doubly attractive for remediation in water.

Researchers have continued to work on cell-based assays for toxicity evaluation of nanoparticles. They found that ceria nanoparticles that will be formed from cerium in diesel fuel additives had a very minor tendency to induce inflammation, much less than zinc oxide. They have discovered that the tendency to cause inflammation is correlated well with the solubility of metal oxides at low pH typical of the compartments in cells that deal with foreign objects. This may offer a suitable fast screening method for assessing the safety of metal oxide nanomaterials that are used widely in nanotechnology. The measurements of the agglomeration of nanoparticles revealed the importance of surface charge. With some materials like iron oxide that have near zero surface charge, it is very difficult to prevent agglomeration in cell growth medium, raising questions about the validity of cell-based assays of toxicity. Researchers have developed a magnetic field system that pulls nanomaterials onto a cell layer before agglomeration can take place, offering a more reliable protocol for toxicity testing with in vitro methods.

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