Publication abstract

Holding Water

M.B. Sanders

For decades, science and engineering disciplines have heralded a time when nanotechnology will provide advances in energy supply, human health and materials sciences that will change the way we live. Although the age of nano-sized robots racing through our blood system repairing damaged tissue and curing disease is a long way off, a large number of consumer and industrial products currently available do utilise nanotechnology in either the manufacturing process or to produce nano-sized particles. It is the fundamental changes in the properties of materials at the nanoscale that is driving innovation and development in the commercial sector.

A nanometer (nm) is one billionth of a meter. Nanoparticles are typically defined as having at least one dimension (e.g. length, thickness, diameter) constrained to 1-100nm. To put this in perspective, human DNA is typically 2-3nm wide. A variety of inorganic nano-sized particles are also produced naturally by processes such as erosion, fire and volcanic activity; however, it is the artificial manufacture or engineering of nanoparticles with specific properties that is causing concern. The same fundamental changes in the properties of materials at the nanoscale, which make them attractive to industrial and medical fields, also make it difficult to predict the fate and effects of these engineered materials in the environment. Over the past 5 years the quantity and variety of engineered nanomaterials available has boomed, particularly in consumer products. Nanoparticles can be found in sunscreens, packaging, food, clothing, medical products and a variety of personal care products(http://www.nanotechproject.org/inventories/consumer/).  As the manufacture and use of a material or chemical increases, the likelihood that that material will end up in the environment, usually the aquatic environment, also increases. Currently, there is a paucity of information on the fate and effects of nanomaterials released into the terrestrial and aquatic environments and it is feared that current ecotoxicology testing and risk assessment strategies may be inadequate for assessing the safety of nano-materials. The Centre for Environment, Fisheries and Aquaculture Science (Cefas), an executive agency of the Department of Food and Rural Affairs (Defra) through collaborations with academia and industry, is developing a tiered testing approach for assessing the risks posed by engineered nanoparticles within the aquatic environment. It is likely that new assessment methodologies, with associated fit-for-purpose testing procedures will be required to address the issues associated with nanotoxicolgy.One of the fundamental difficulties in investigating the threats posed by nanoparticles has been identifying which property of the particle, if any, poses the threat? Is it their physical size, structure, surface charge, post manufacture modifications (e.g. coatings) or other aspects of nanoparticles that differ to larger particles (>100nm) of the same material? Historically, the availability of highly characterised homogenous materials has severely hindered investigations into nanotoxicity; especially in aquatic environments where the surface chemistry of nanoparticles is often influenced and modified by the complex organic and inorganic components present, thereby altering their behaviour and fate. In order to investigate these aspects Cefas has fostered collaborations with Dr. Paul Christian at the University of Manchester and Dr. Jamie Lead at the University of Birmingham to produce materials suitable for investigating nanotoxicity in aquatic environments.

Using cadmium sulphide (4nm ±1nm) and silver (13nm ± 7nm) nanoparticles stabilized with polyethylene glycol as model nanoparticles we have investigated nanoparticle effects on both cell cultures and aquatic species. Under standard test conditions little difference between silver and nano-silver was observed, however, the presence of light had a significant effect on toxicity. Other studies involving fish have identified impacts on gene expression, biochemical processes, cell structure and reproductive behaviour following exposure to different nanoparticles. These studies are by no means definitive, but suggest that current assessment methodologies may need to be revised to account for novel effects of nano-sized particles. Cefas is currently collaborating with Exeter University and other organisations to investigate the potential environmental impacts of cerium oxide, the diesel fuel additive, and zinc oxide, a major constituent of many sunscreens. This work is being funded under the Defra LINK programme PROSPeCT’ (Ecotoxicology Test Protocols for Representative Nanomaterials in Support of the OECD Sponsorship Programme).

Reference

M.B. Sanders (2009) Holding Water. Public Service Review: Science & Technology, 4, 128-129