Suggested strategies for the ecotoxicology testing of nanoparticles
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Suggested strategies for the ecotoxicology testing of nanoparticles V. Stone, T. F. Fernandes, A.T. Ford and N. Christofi. Centre for Health and the Environment, School of Life Sciences, Napier University, Merchiston campus, Edinburgh, EH10 5DT, UK. [email protected] Introduction Nanotechnology is a rapidly developing field of science, technology and innovation. Nanotechnology involves the development and manufacture of materials in the nanometer size range and includes the production and use of nanoparticles (NP; particles with at least one dimension of less than 100 nm). Due to their small size a relatively large proportion of the atoms and molecules making up the particles are exposed at the particle surface compared to larger particles. This structural difference coupled with the relatively large surface area per unit mass of NP allows such materials to exhibit properties that differ from bulk chemicals, making them useful in a wide variety of applications including electronics, paints, cosmetics, medicines, foods, textiles and environmental remediation. This means that the potential for exposure to nanoparticles both in an occupational setting and as consumers is large. Nanoparticle toxicology In general, there is a lack of information regarding the human health and environmental implications of engineered NP (Colvin, 2003). Some toxicological studies have been conducted in relation to the inhalation of NP made from low toxicity materials such as carbon black (Li et al., 1999), TiO2 (Ferin et al., 1992) and polystyrene (Brown et al., 2001). Such studies demonstrate that the toxicity of these materials is related to their ability to induce oxidative stress and inflammation in the lung leading to impacts on lung and cardiovascular health. The cells of the body contain a number of antioxidant defence molecules (e.g. glutathione and vitamin E) that protect cells against reactive oxygen species (ROS) and free radicals that due to their electrophillic properties damage proteins, lipids and DNA. Such ROS and free radicals include superoxide anion radicals (O2-.) and hydroxyl radicals (OH.) and are generated at the surface of NP (Stone et al., 1998, Wilson et al., 2002). Depletion of antioxidant defence molecules by these ROS and production of free radicals lead to oxidative stress and damage to cells. Nanoparticles causing oxidative stress may also lead to the production of reactive nitrogen, sulphur and other species (i.e. RNS, RSS and others) stressing the body in a similar manner to the effect of ROS. In the case of RSS (Giles and Jacob, 2002), reactive sulphur substances such as thiyl radicals and disulphides can oxidise and ultimately inhibit thiol proteins and enzymes. Oxidative stress and cell damage can also activate inflammation. This involves activation of various white blood cells within the immune system. Such cells include macrophages that migrate to the site of particle deposition and then engulf the particles by phagocytosis. The macrophages then remove the particles from the lu
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