1. the detection of the particles in the environment
2. the measurement of emissions of nano-particles
3. the life-cycle of the particles in the environment
4. the toxicity of the particles to the environment
5. the impact on the immediate and longer range environment

Examples of how risk could occur

1. Waste streams from industrial plants being discharged into streams and rivers
2. Accidental releases from production and during transportation of nanoproducts into streams, rivers and the atmosphere
3. Domestic nano waste discharge from the use of nanotechnology in cosmetics, toiletries and sun creams

There is a lack of information on nanoparticles entering the environment, and what the health risks and consequences to the environment these particles could have. Once the nanoparticles enter one ecosystem they could move to another, for example, the movement of nanoparticles between water and sediments, or the absorption of atmospheric particles into water.

The main concern will be if any of the nanoparticles entering the environment are toxic or could become toxic to living species in the environment. For example, there is the possibility of nanoparticles being toxic to microorganisms in the soil and groundwater. Following on from this would be possible hazards from the nanoparticles or from consuming the microrganisms affected by the nanoparticles for fish, insects or mammals. There is also a risk to plants from nanoparticles which again could have a follow-on effect on the food chain. For example the deposition of atmospheric particles on crops could provide another route for toxic or reactive nanoparticles into the food chain.

Nanoparticles entering the environment may not initially be toxic to living species in the environment, but they could in their lifecycle become toxic. The nanoparticles could react to other substances in the environment, break-down in the environment, provide a catalyst (speeding up) for the reactions already taking place, or prevent essential reactions taking place. Measuring these effects would require a complete understanding of the nanoparticles themselves, the reactions taking place in the environments encountered by the particles, and the lifecycle of the nanoparticle. For example, waste nanoparticles from a manufacturing plant entering a stream could alter the pH of the stream. Altering the pH of a stream can lead to metals that are not normally soluble dissolving, such as aluminium. Aluminium in the water supply would in turn be toxic to living things in the stream.

When considering the analysis of the nanoparticles consideration needs to be given to the size, shape, surface and bulk of the particles. These could all influence the properties of nanoparticles, so must all be considered when assessing the risk of the particles.

There are therefore many factors to be taken into account when aiming to detect and analyse the nanoparticles in an environment. The influence of the environment on the particles and follow on effects must be considered alongside the toxicity of the nanoparticles themselves.

There are many methods of analysis for both physical and chemical properties of particles, however due to the size of the nanoparticles not all methods will work, or require research themselves to modify them. Both quantitative detection, and analysis of the nanoparticles is required.

Examples of methods that are successfully being used to measure nanoparticles in different environments include a system called  a scanning mobility particle sizer (SMPS) used for measuring aerosols, which can be applied to measure nanoparticles in the gas phase. There are techniques for detection of nanoparticles in the liquid phase, such as optical chromophore counting, resonant light scattering and Raman scattering techniques, as well as the use of microscope techniques such as Scanning Transmission Electron Microscopy (STEM), or High Resolution Transmission Electron Microscopy (HRTEM). A problem that can be highlighted with using these techniques is that often sampling is required and treatment of the samples before the actual analysis of the sample. This not only increases error in quantity analysis but also prevents in-situ analysis of the nanoparticles in the environment they are in.

Therefore different environments and ecosystems need to be considered for detection and analysis of nanoparticles. These different ecosystems have different mediums, mainly, solid, liquid or gas. However within these main types of medium are variations such as plant tissue and cells, and soil types. These provide challenges to methods of detection and analysis.  The nanoparticles could also be present within consumer products and nanocomposites which also provide challenges to detection and analysis. 

It is important to remember that nanotechnology can be used in a positive way in the environment, for example, the use of nanoparticles for groundwater and contaminated land remediation. However the risks of the nanoparticles in their life cycle in the environment must be established.

Website links for summarising the environmental risk of nanoparticles

The national nanotechnology initiative: A book by the US national research council. 

The potential risks of nanomaterials: A review carried out by the ECETOC on  published in 2006.

The potential risks posed by engineered nanoparticles: A review by DEFRA in 2005.

Measuring nanoparticles: Examples of methods that are successfully being used to measure nanoparticles in different environments, SCENIHR report.

Reports on emerging nanotechnologies