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FATE, TRANSFORMATION AND TOXICITY OF MANUFACTURED NANOMATERIALS IN DRINKING WATER

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Impact/Purpose:

Although the current market for nanomaterials is small and their concentration may not be high enough in the environment to cause human health or environmental problems, this market is increasing rapidly and the discharge of nanomaterials to environment in the near future could be significant as manufacturing costs decrease and new applications are discovered. The accumulation of nanomaterials in cells may have significant environmental and human impacts. However, at present, very little is known about the fate, transport, transformation and toxicity of these man-made nanomaterials in the environment. The objectives of this project are: 1) to characterize the fundamental properties of nanomaterials in aquatic environments; 2) to examine the interactions between nanomaterials and toxic organic pollutants and pathogens (viruses); 3) to evaluate the removal efficiency of nanomaterials by drinking water unit processes; and 4) to test the toxicity of nanomaterials in drinking water using cell culture model system of the epithelium. This study considers the physical, chemical, and biological implications of nanomaterial fate and toxicity in systems that will provide insight into the potential for nanomaterials to be present and of health concern in finished drinking water.

Description:

Studies were conducted using several types of commercial metal oxide nanoparticles (two types of titanium dioxide, iron(III) oxide, zinc oxide, nickel oxide, and silica in powder form or liquid suspensions), functionalized quantum dots, lab-synthesized hematite nanoparticles and aqueous fullerenes (nC60). Most experiments were conducted with 10 mg/L of the nanoparticles. Among the analytical methods developed, a solid phase extraction and LC/MS method was developed to quantify C60 at ppb concentrations in complex water matrices. Aggregation studies were conducted in the presence of simple salts to compress electric double layer of the nanoparticles, to study their aggregation rates. Increasing salt concentrations lead to aggregation. CdTe quantum dots (QDs) containing carboxylic functional groups were stable in the presence of monovalent salts, but aggregated rapidly upon addition of di- or tri-valent cations (Ca, Mg, Al) that complexed with the functional groups on the quantum dots. Adding natural organic matter stabilized most nanoparticles (i.e., less aggregation). The fate of nanoparticles during drinking water “jar” tests using aluminum sulfate as a coagulant was characterized by changes in dynamic light scattering, zeta potential, scanning electron microscopy (SEM), and acid digestion followed by atomic absorption spectroscopy. Metal oxides and hematite rapidly aggregated in the presence of simple salts, local tap water, and addition of aluminum sulfate.

Trans-Epithelial Electrical Resistance (TEER) measurements have been made using Caco2 BBe (human intestinal cells) grown and maintained with Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 10 percent fetal bovine serum, penicillin/streptomycin/ fungizone, and transferrin. Nanoparticles were applied to the tests in the medium. Controls were conducted without nanoparticles or with sodium azide. Aggregation within the medium was observed. Measurements included TEER, live/dead assays, confocal microscopy and SEM imaging, and quantification of passage of nanomaterials across the membrane. Nanoparticles were found to flatten down the microvilli, allowed passage of 1% to ~10% of the nanoparticles, and result in >25% decrease in TEER relative to controls only at very high nanoparticle dosages.

This study developed a novel technique to prevent aggregation of QDs by diluting the QDs in calcium/magnesium-free phosphate buffered saline, while retaining conditions on one side of the epithelial sheet to provide necessary nutrients and co-factors to the cells. Toxicity studies completed here show that the QDs purchased for these experiments caused disruption in the epithelium monolayer and cell death.

Record Details:

Record Type:PROJECT( ABSTRACT )
Start Date:10/01/2004
Completion Date:09/30/2007
Record ID: 89202