Development of international standards for nanotechnology and risk assessment of nanomaterials

Abstract

With the rapid growth of nanotechnology-based consumer products containing silver, gold, carbon, zinc, titanium, and silica nanoparticles, the potential for exposure to nanoparticles is also increasing, and workers in nanotechnology-based industries are particularly at risk. Yet, despite an increased concern over the inhalation toxicity of nanoparticles, there are currently no generally accepted methods of inhalation toxicology testing for nano-sized particles and no specific nanoparticle generation methods. For an accurate evaluation of the health effects of nanoparticle inhalation, nano-sized particles need to be generated and transported to a test environment with experimental animals to investigate the short- and long-term inhalation toxicity. Thus, the metal particle nanoparticle generation standard (ISO 10801) based on the evaporation and subsequent condensation of metal (silver and gold in this case) is capable of providing a consistent particle size distribution and stable number concentration suitable for short- or long-term inhalation toxicity studies. Meanwhile, when conducting inhalation toxicity studies of nano-sized particles, it is also important to monitor the concentration, size, and distribution of the nano-sized particles in the inhalation chamber. Therefore, standard ISO 10808 suggests a battery of tests for monitoring the inhalation toxicity testing chamber, including a Differential Mobility Analyzing System (DMAS) to measure the particle number, size, distribution, surface area, and estimated mass dose, as well as a morphological examination using Transmission Electron Microscopy (TEM) or Scanning Electron Microscopy (SEM) and an Energy Dispersive X-ray Analyzer (TEM-EDXA) to determine the chemical composition. Conventional mass dose monitoring and other physicochemical monitoring are also included if deemed a necessary parameter for determining the toxicity. Consequently, the above mentioned standards would appear to be very useful for assessing the risks of inhalation exposure to nanoparticles and providing a solid basis for nanoparticle generation and dosimetry for toxicology.