Nanomaterials - What are they?
Nanomaterials are microscopic particles in the nanometre (nm) scale. One nanometre is one millionth of a millimetre. By comparison, a human hair is approximately 70,000 nm in diameter, a red blood cell is approximately 5,000 nm wide, and E. Coli bacteria are approximately 2000nm in length.
Nanoparticles exist in nature, e.g. milk contains nanoscale droplets of fat and every cell in your body relies on nano sized protein complexes to function. The manufacture of engineered nanomaterials is a rapidly developing area with many applications. They benefit several different industries e.g. energy storage, technology, healthcare, construction and cosmetic products.
Nanoparticles are also produced as a by-product of many long standing processes, such as fires, diesel engines and high energy manufacturing processing such as welding or grinding.
The WHO definition of a nanomaterial is:
‘A natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm - 100 nm.
In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50 % may be replaced by a threshold between 1 and 50 %.’
However, with any new innovation there come uncertainties as to whether the unique properties of engineered nanomaterials pose a risk to health.
Nanomaterials – What is the risk?
Their smaller nature make nanoparticles more reactive, easier to inhale and able to pass through skin and membranes in the body. They may have different physical and toxic properties compared to larger particles of the same material.
These factors lead to an uncertainty of how they interact with our bodies and whether they can cause ill health.
Not all nanomaterials are hazardous, however those which are will have varying degrees of hazard associated with them.
The hazardous properties of engineered nanomaterials are determined by their physical properties, e.g. size, shape, crystal structure, surface coating, surface reactivity etc. and their chemical composition.
Skin Risk
With the exception of nanomaterials that are used in cosmetic products, there have been few investigations into the effects of nanomaterials on the skin. Any effects that do arise because of skin contact are expected to be site-specific contact effects. Research into the skin absorption potential of nanomaterials has suggested that if there is any absorption across the skin the amounts that are absorbed will be low.
Inhalation Risk
Emerging evidence indicates that when some types of Carbon Nano Tubes (CNTs) and other biopersistent High Aspect Ratio Nanomaterials (HARNs) are breathed in they can cause inflammation and fibrosis in the lungs and these effects may be irreversible. However, there is insufficient data to confirm the health consequences of long-term repeated exposure. There is also some evidence that types of CNTs and HARNs can cause skin inflammation.
What is a HARN?
A particle is said to have a high aspect ratio when one or two of their dimensions are much smaller than the others, e.g. a fibre. A particle with an aspect ratio greater than 3:1 would be considered a HARN and capable of reaching the deep lung if inhaled.
There is evidence that HARNs with all of the characteristics below may be retained within the narrow space surrounding the lungs – the ‘pleural cavity’ – for long periods;
- thinner than 3 µm
- longer than 10–20 µm
- biopersistent
- do not dissolve/break into shorter fibres
It is known that long fibres that are retained in the pleural cavity can cause persistent inflammation, which may lead to irreversible diseases such as fibrosis and lung cancer.
What is a CNT?
Carbon Nano Tubes are manufactured, three-dimensional forms of carbon. Some CNTs exist as long, straight fibres and can cause inflammation and fibrosis in the lungs and these effects may be irreversible.
Nanomaterials – What do I need to do?
The manufacture and use of nanomaterials at work fall under the Control of Substances Hazardous to Health Regulations NI 2003 (COSHH). If the chemical and physical properties of the nanomaterial mean that they can give rise to a risk of fire and explosion then the Dangerous Substances and Explosive Atmospheres Regulations (NI) 2003 (DSEAR) also apply.
Under these regulations if your work involves the manufacture or use of engineered nanoparticles you must carry out a risk assessment. This will enable you to identify the dangers posed by the material and your process and what you need to do to eliminate or reduce the risk.
Nanomaterials are substances of high concern and unless, or until, sound evidence is available on the hazards from inhalation a precautionary approach should be taken to manage the risk. In view of the evidence for lung damage and lack of information on the effects of long-term repeated exposure, a higher level of control is warranted for CNTs and biopersistent HARNs.
Control Measures
The hierarchy of control in the COSHH regulations should be followed when identifying suitable control measures.
Elimination – Use alternatives to nanomaterials.
Substitution – Use safe alternative; use the materials in solutions or slurries.
Engineering controls – Local exhaust ventilation (LEV) systems e.g. total enclosure or partial enclosure/ fume cupboard will be reasonably practicable in many processes involving manufacturing/synthesis or weighing of nanomaterials. Other types such as capturing, receiving hoods or down draught benches may be suitable for cutting, sawing, polishing of composite nanomaterials.
PPE – appropriate types should be selected depending on the material and activity.
When RPE is used as a primary control, i.e. the only method of control (not recommended unless no other method available):
- Use a full-face respirator with APF 40, preferably powered if used for over one hour.
When RPE is used as a secondary control for emergencies or accidental spillages or where additional protection is required as indicated by the risk assessment:
- Disposable and half face respirators should have an assigned protection factor (APF) of no less than 20.
Health Records
Exposure to nanomaterials does not meet the criteria requiring health surveillance under the COSHH Regulations, since, as yet, there are no tests or health screening method and no links with occupational disease. As a minimum though, you should keep a record of all those working with nanomaterials, through the equivalent of a COSHH health record form, as you would for other substances of concern.
Resources
Further information can be found at:
- HSE Nanotechnology website - HSE (GB)
- Using Nanomaterials at Work (HSG272) HSE (GB)
- Working Safely with Nanomaterials in Research and Development - UK Nano Safety Group
- Local Exhaust Ventilation (LEV)
- Respiratory Protective Equipment