Guidelines for working with nanowires and silica dust
The health implications of inhaling nanowires (carbon, Si ...) are not yet fully investigated nor understood. The approach that we take is to assume that there might be a potential health risk associated with the inhalation of nanowires. The reason for this assumption is that the dimensions of nanowires and asbestos are similar. This means that the risk is associated to the ratio of the length of the wire divided by its diameter being larger than 3 and smaller than 10. The dimensions that might potentially cause the highest health risk are:
8 µm < l < 100 µm (l = length)
d < 250 nm (d=diameter)
l/d > 3
As a consequence, we suggest that certain precautions are taken when working with nanowires in order to minimise the risk of inhaling them.
The health implications of inhaling Si dust are well known. Inhalation of small particles (< 5 mm) of silica dust leads to silicosis. This is a serious lung disease which can cause permanent disability, cancer and can lead to early death. It is clear from the HSE guidelines that silicosis will be a problem when exposure levels are high.
On Mon & Tues 9, 10 June 2008 we (organised by J. Cotton) invited James Wheeler, who is a HSE Specialist Inspector from CSD3 CRMU (Chemical Substances Division) based at Bootlev, to gather contextual information about the handling of nanoparticles in the laboratories on level 7 of the Electrical and Electronic Engineering department. The tests were done before and during typical experiments that are done with nanowires and microdust in the labs. No difference was found between the background measurement and the measurement while the experiments were taken place.
Analysis of results
This means that the volumes of particles/dust that become airborne during the experiments are so low as to be immeasurable. Especially in the case of silica dust, this means that there is no reasonable risk for silicosis under the given experimental conditions. Good housekeeping is sufficient for doing safe work.
For nanowires it also means that the volume of airborne wires is extremely small and therefore the risk to other people in the group or the department is negligible small. The risk for the experimentalist however might still be non-zero and therefore precautions are advised for the experimentalists using Si nanowires.
Note that short term exposures of low concentrations of airborne wires/dust is likely to be associated with a very low health risk.
The health risks associated with nanowires and microdust are both based on airborne particles. Therefore reduction of the hazard associated with wires and dust is to minimise possibility of generating airborne particles.
Hazard reduction instructions are:
- Hygienic work conditions (no eating nor drinking, wet cleaning of surfaces after experiment and washing of hands after experiments).
- PPE (gloves, face-mask (see below)) can be worn. Note that the effectiveness of a face mask for very small particles is not proven.
- Use under extracted bench (The fume hood to be used is the one in the packaging lab level 7 EE building (the left one that looks different from the others)).
- Keep process wet as long as possible.
- Cleaving of nanowire arrays is strictly forbidden.
- Clean surface with wet wipes to prevent making them airborne and dispose in closed plastic bag.
- Consume any left over nanowires/microdust by wet etching in order to keep volumes small.
If you are working with large densities of dry wires it is recommended to use a half-mask. People who wish to use a half-mask need to go to the Safety Unit for a face mask fitting.
The safety unit can be found at:
Imperial College Safety Department
Level 5, Sherfield Building
South Kensington Campus
London SW7 2AZ
One important note:
Personal protective equipment (PPE) such as a face mask is only the last resort in order to keep yourself safe. So it is much more important to prevent wires from escaping by good practice and working under the fume hood than it is to do silly things and wear a facemask.
Also remember that the dimensions of the particles are small in one direction, so your mask should ensure that dimension cannot get through. This means that not any face mask will do.
More info on health and safety in nanotechnology can be found on:
You are strongly advised to read the risk assessment information available on that webpage:
At the moment there is no requirement for a COSHH form when using nanowires/-particles as there is not sufficient information available to make a reliable assessment.
When more information becomes available, this situation might change.
The current advice is to limit the exposure possibility by good working practices as suggested above.