(260ae) Material and Toxicity Evaluations of Nanoclays throughout Their Life Cycle
The incorporation of nanoclays, layered mineral silicates, into polymers leads to the formation of nanocomposites with enhanced mechanical strength, UV dispersion, barrier, and flammability properties. With proper exfoliation of nanoclays into polymers, these nanocomposites can then be applied to different industries, from automotive, to medical, or food packaging. However, with increasing implementation into such industries it is important that we begin to investigate the physical and chemical changes that nanoclays undergo throughout their life cycle as well as evaluate any toxicity during their life cycle to thus ensure both worker and consumer health. Herein, we examined the physical and chemical characteristics of 4 nanomer nanoclays (1 pristine and 3 organically modified) in raw or â??as-receivedâ?? form to mimic a manufacturing environment, and after their thermal degradation, to mimic end-of life cycle in incineration plants. Material characterization was performed via microscopical and spectroscopical techniques while the toxicity evaluations used in vitro testing on human bronchial epithelial cells (BEAS-2B). Dose response curves were obtained via live cell counts to determine the degree of toxicity of each â??as-receivedâ?? nanoclay and its thermally degraded byproduct. Thermal degradation caused for breakdown of the nanoclay platelet structure and loss of organic modifiers of the organically modified clays. The â??as-receivedâ?? nanoclays had lower IC50 values relative to their thermally degraded counterparts, with a range in IC50 values of 10-325 Âµg/ml and 150-400 Âµg/ml for â??as-receivedâ?? and thermally degraded nanoclay, respectively. While more studies are needed to examine the mechanism of toxicity of these nanoclays, our results reveal that these nanomaterials have the potential to induce inhalation toxicity in both manufacturing and disposal environments, with the degree of toxicity being dependent on their physical and chemical properties.