Carbon nanotubes and work health and safety
Carbon nanotubes may be described as seamless cylinders of rolled-up graphite. They are manufactured as two types; single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Because of their structure, carbon nanotubes can possess high strength, high flexibility and high electrical and thermal conductivity. These properties give rise to potential applications in a number of industries including the electronic, automotive, and energy industries with significant benefits.
The use and manufacture of carbon nanotubes is not currently widespread in Australia. However they are currently used in many research facilities in Australia and are embedded in some imported products, such as high-performance sporting equipment, because of their capacity to increase strength at low weight.
Hazardous properties of carbon nanotubes
Discrete carbon nanotubes are fibre-like, but can readily agglomerate to form particle-like or rope-like structures. Research findings in mice have indicated that relatively straight, long MWCNTs may be hazardous in a similar manner as other pathogenic fibres like asbestos when inhaled, and are a potential mesothelioma hazard, but that shorter fibres or particle-like structures do not have these fibre-like hazards.
Following on from these findings, Safe Work Australia commissioned a collaborative experimental research project involving the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the University of Edinburgh (UK) and the Institute of Occupational Medicine (UK), to study the durability of carbon nanotubes and their inflammatory impact in mice.
The research found that the durability and hazards of all types of carbon nanotubes are not necessarily the same:
- Carbon nanotubes can be durable but may also break down in simulated lung fluid, depending on the type of sample
- If they are fibre-like and sufficiently long, carbon nanotubes can induce asbestos-like responses in mice, but this response is significantly reduced if the nanotubes are less durable
- Tightly agglomerated particle-like bundles of carbon nanotubes did not cause an inflammatory response in the peritoneal cavity of mice which is sensitive to long, durable fibres but not to compact particles or short fibres
This research in mice supports previous findings that some forms of carbon nanotubes may have asbestos-like properties, but other forms do not. It also shows that if carbon nanotubes can be manufactured to be non-durable in lung fluid, these properties can be avoided.
While this research indicates that shorter carbon nanotubes or bundles of carbon nanotubes may not be hazardous in the outer lung region and thus may not be a mesothelioma hazard, they can still cause an inflammatory response and be hazardous in the lungs.
Thus all carbon nanotubes should be handled with high levels of caution in the workplace to avoid inhalation, unless hazard information on the specific material indicates otherwise.
Classification of carbon nanotubes as hazardous chemicals
Following on from the research by CSIRO and partners, Safe Work Australia commissioned the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) to undertake an assessment of the health hazards of carbon nanotubes for classification under the hazardous chemicals regulations.
NICNAS recommended that unless product-specific data suggests otherwise all carbon nanotubes are classified as hazardous with the following GHS hazard statements:
- Suspected of causing cancer.
- May cause damage to lungs/respiratory system through prolonged or repeated inhalation exposure.
Classification of a chemical as hazardous means that there are mandatory requirements under work health and safety laws, including requirements for workplace labelling and Safety Data Sheets.
See: The research report, Human health hazard assessment and classification of carbon nanotubes and associated information sheet
Guidance for the safe handling and use of carbon nanotubes
To help people work safely with carbon nanotubes, Safe Work Australia commissioned the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to develop the guidance document Safe Handling and Use of Carbon Nanotubes. CSIRO has significant experience in working with carbon nanotubes.
The guidance in this document is applicable to other forms of carbon nanofibres, such as carbon nanorods and carbon nanowires. It is also applicable to products containing carbon nanotubes and other forms of carbon nanofibres where these nanomaterials may be released during handling.
See: The guidance document, Safe Handling and use of carbon nanotubes and associated information sheet
Measuring emissions and exposures to carbon nanotubes in the workplace
Safe Work Australia has commissioned research by CSIRO and Queensland University of Technology/Workplace Health and Safety Queensland to progress the development of measurement techniques.