Nanomaterials are defined as any material, natural or manufac tured, that has at least one dimension that lies between 1 and 100 nanometers (nm) in size. The Stanford University Health and
Safety Department gives a more precise definition at https://ehs.
stanford.edu/topic/hazardous-materials/nanomaterials.
Nanomaterials have been of increasing commercial interest and are now used for an extraordinary range of purposes. In the phar maceutical manufacturing industry, nanoparticles are being tested and used to deliver cancer chemotherapeutic and other drugs.
Currently produced nanomaterials include gold, silver, cadmium, germanium, ceramic, and aluminum oxide nanowires; carbon, silicon, and germanium nanotubes; zinc oxide nanocrystals; gold nanowafers; and copper oxide nanocubes. The increasing use of nanomaterials has led to release of these nanoscale substances into the workplace and the general environment. Because nanomaterials behave in unique patterns of chemical and physical reactivity, their toxicology is often novel and there is insufficient information on the likely human or environmental impact of dispersal of these manufactured products in the environment. The University of North Carolina laboratory safety and health manual outlines the problems of working with nanomaterials in the laboratory and their safe use at http://ehs.unc.edu/manuals/laboratory/chapter-18/.
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Human toxicology—Inhalation, oral ingestion, dermal absorption, and parenteral administration of nanomaterials have been the sources of human exposure. Because of the unique physicochemical properties of nanomaterials, their toxicity may be similar to or very different from the larger, bulk materials encountered in traditional toxicology studies. The nature of the exposure will impact the likelihood that nanomaterials will reach target organs or cells. Nanomaterials can cross cellular membranes, penetrate nuclear material and genetic information, and may impact cellular response at a nanoscale. Silica nanoparticles have been demonstrated to produce kidney toxicity in humans, and zinc oxide nanoparticles are toxic to human liver cells. Multiwalled carbon nanotubes have been found to be cytotoxic in human lung cells. Titanium dioxide nanoparticles that are widely used in sunscreens, other cosmetics, pharmaceuticals, and many other products have been noted to be toxic in the lungs and elsewhere.
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Environmental toxicology—Nanomaterials can enter the environment at all stages of their industrial life cycle, including manufacturing, delivery, use, and disposal. When nanomaterials are placed into waste streams they may enter water systems, or be carried by wind or soils, and enter the food chain. An EPA fact sheet on nanomaterials in the environment is available at https://www .epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_ emergingcontaminant_nanomaterials_jan2014_final.pdf.
The increasing production of nanomaterials and their multiple uses has led to environmental contamination. Many species, including bacteria, small mammals, and fish and other aquatic organisms have been studied in laboratory assessments of nanomaterial toxicity. The ecotoxicology of nanomaterials remains an area of deep concern and ongoing research.
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