Are Tungsten Carbide Cobalt Nanoparticles Harmful to Health?
Chemical-physical Measuring Methods as Basis for the Investigation of Potentially Harmful Effects
- Photo: Susanne Bastian, Department of Pediatric Neurology, University Children’s Hospital Carl Gustav Carus, Technical University of Dresden 
- Fig. 1: Electron microscope image of a cell of the central nervous system (glia cell), which shows inclusions of tungsten carbide particles (12,500-fold magnification). Photograph: Armin Springer, Max Bergmann Center of Biomaterials, Technical University of Dresden
- Fig. 2: Electron microscope image of tungsten carbide particles in powder form. Photograph: Dr. Volkmar Richter, Fraunhofer Institute for Ceramic Technologies and Systems (IKTS)
Tungsten carbide and tungsten carbide cobalt nanoparticles can enter cultured mammalian cells. This finding emerges from a study conducted by scientists from Dresden University, the Leipzig Helmholtz Centre for Environmental Research (UFZ) and the Fraunhofer Institute for Ceramic Technologies and Systems in Dresden (IKTS). However, the results show that nanoparticles of pure tungsten carbide do not have any cytotoxic effects. These are only produced when the nanoparticles are mixed with toxic substances such as cobalt.
In the in vitro study, which has been published in the well-respected journal Environmental Health Perspectives, the researchers investigated the effect of tungsten carbide and tungsten carbide cobalt nanoparticles with an aggregate size of 150 nanometers on cell cultures derived from human lung, skin and intestinal cells as well as from rat brain cells. The hard tungsten carbide is used predominantly for tool manufacture. The addition of cobalt increases toughness and strength. During the manufacture of the tools, people in that working environment might become exposed. However, there had not been any findings available on the effects of the material in nanosize particles to date. Before considering using nanoscale raw materials more widely, the risks for humans and the environment should first be investigated and considered. The chemical and physical investigations confirm that both tungsten carbide and tungsten carbide cobalt particles are stabilized by albumin or serum in nutrient solutions. This is an important finding, since potentially harmful effects might be produced by the small size of the particles. Adding albumin to the nutrient solutions makes it possible to carry out research in conditions that are very close to those found in exposed organisms. First, using electron microscope procedures, it was possible to demonstrate the uptake of the particles by the cells under examination. During the subsequent biological tests, it was found that tungsten carbide nanoparticles on their own are not acutely toxic, whereas mixtures of these particles with cobalt had a toxic effect at higher particle concentrations. The detected toxicity of the WC-Co mixture was higher than that of cobalt ions in comparable concentrations.
Why the combination of tungsten carbide and cobalt has a more toxic effect has not been finally determined. It is possible that nanoparticles act as "Trojan horses", i.e. they increase the uptake of toxic cobalt ions by the cells. In the researchers' view it is important to investigate the influence of particle size and the effects of mixing materials further and to derive possible conclusions for health risk assessments. The German Federal Ministry of Education and Research (BMBF) has provided funding totaling € 7.6 million to three large consortia (NanoCare, INOS and TRACER), which were the first to carry out large-scale investigations into health-relevant aspects of synthetic nanoparticles. INOS' contribution focused on developing methods to assess the risk potential of technical nanoparticles with the aid of in vitro procedures. This work concentrated on ceramic and metallic particles such as diamond, tungsten carbide, titanium dioxide, titanium nitride, cobalt, platinum, ceramic metal compounds as well as carbon nanotubes and carbon black.
 Bastian S. et al.: Environ.Health Perspect 117(4), 530-536 (2009)