Nanotechnology involves the creation and/or manipulation of materials at the nanometre (nm) scale (1-100nm) either by scaling up from single groups of atoms or by refining or reducing bulk materials.
A nanometre is 1 x 10-9m or one millionth of a millimetre. To give a sense of this scale, a human hair is of the order of 10,000 to 50,000 nm, a single red blood cell has a diameter of around 5000 nm, viruses typically have a maximum dimension of 10 to 100 nm and a DNA molecule has a diameter of 2 - 12 nm.
Health and Safety Concerns
It is widely accepted that there is at present a lack of information and knowledge concerning the implications of manufactured nanomaterials on human health and the environment. Concerns have been voiced in several academic papers regarding potential risks to health that may arise during the manufacture, manipulation, use and disposal of these materials.
There are major concerns regarding the potential risks to health from the inhalation of nanoparticles (NPs) and, following evidence published in 2008 in Nature Nanotechnology particular concern regarding carbon nanotubes (CNTs). Concerns have also been voiced about the potential risks to health from dermal exposure or ingestion and the possible risk of fire and explosion.
The Control of Substances Hazardous to Health 2002 Regulations (as amended) are the regulations that relate to the use of chemicals and other hazardous substances in the UK. The Regulations require that, in order to prevent ill health, employers control the exposure of their employees and others to hazardous substances, this to a level that is as low as is reasonably practicable. In common with most modern health and safety legislation the COSHH Regulations are risk assessment based and require that risk assessment is undertaken to arrive at conclusions as to which methods of exposure controls are appropriate and sufficient to ensure prevention or adequate control of exposure.
In order to undertake a suitable and sufficient assessment of risk one has to have good information regarding the hazardous properties of the substances, their health effects and the effectiveness of preventive and control measures which have been or will be taken.
Of concern is the uncertainty that is introduced into any risk assessment involving exposure to nanomaterials because of the knowledge gaps concerning their health hazards. Where there are gaps in knowledge the more cautious and robust the risk assessment should be.
For example it should not be assumed that a material in nano range size will exhibit the same hazard potential as that same material in a larger size. When introducing control measures, related to exposure to nano range sized materials, one should always err on the side of caution and aim to control for the most serious risk scenario.
HSE Report 274 advises that 'For air velocities prevailing in workplaces, airborne nanoparticles can be considered as having no inertia. They will therefore behave in a similar way to gas and if not fully enclosed will diffuse rapidly and will remain airborne for a long time. Because of their high diffusion velocity, these particles will readily find leakage paths in systems in which the containment is not complete. Engineering control systems designed for use to control nanoparticles such as enclosures, local exhaust ventilation (LEV), fume cupboards and general ventilation therefore need to be of similar quality and specification to that which is normally used for gases rather than particulate challenges'.
HSE's Information Sheet 'Risk management of carbon nanotubes' advises that exposure should be controlled at source by carrying out all tasks, including packaging for disposal, in a ducted fume cupboard with HEPA filter, or by using other suitable effective local exhaust ventilation with HEPA filter. HSE considers ductless fume cupboards and recirculating biological or safety cabinets unsuitable for use with CNTs, because these methods do not control exposure so that risks are reduced as low as practicable. HSE also advises that respiratory protective equipment should only be used for emergencies and then in addition to other control measures. Any provided RPE should have an assigned protection factor (APF) of 40 or higher, users must have been trained in its use and face fit tested on the type and model of respirator that they are to use.
In the UK issues relating to fire and explosion are covered by the Dangerous Substances and Explosive Atmospheres Regulations 2002. If it is thought that risk of explosion and fire, due to the manipulation of nanoparticles, is an issue then a risk assessment must be undertaken in order to comply with these Regulations and suitable control measures implemented to control such risk to a suitably acceptable level.
Ease of ignition and violence of a dust explosion tend to increase as the particle size decreases. Whilst this tendency levels out for many dusts at particle sizes in the tens of micrometers, a particle size limit below which dust explosions cannot occur has not been established, and so it is therefore prudent to assume that many nanoparticle types will have the potential to cause an explosion. Unfortunately, at present there is almost no data available on the fire and explosion hazards of nanoparticles. Current advice is to take risk reducing precautions and explosion protection measures in line with those commonly implemented for dust control and dispersion of hazardous quantities of dust particles of a larger size.
Competence of person undertaking the risk assessment
The current state of knowledge and in particular the large knowledge gaps, concerning the creation and manipulation of NPs and CNTs suggests that it would be difficult and inappropriate for a person with no prior background knowledge of nanomaterials risk issues to make effective judgements as to appropriate steps that may need to be taken and implemented in order to ensure that risk is reduced to the lowest level practicable. It is strongly recommended that those involved in undertaking and developing risk assessments for work processes involving nanomaterials seek information from as wide a combination of sources and in particular consult with those already working in the ever-growing nanotechnology world. In an effort to aid this some sources of information are offered below.