Nanomaterials are incredibly small particles that offer extremely large benefits for many different consumers, products and industries. They also have negative characteristics that are yet not fully understood. Jon Herbert reports.
Nanomaterials are by definition small. Often, they are no larger than a single atom or molecule. Even so, they perform astonishing tasks: nanomaterials are revolutionising the commercial manufacturing environment and are already all around us on an industrial scale.
At 10,000 times smaller than the diameter of a human hair, their minute size, shape and enormous surface area mean that they can also act and react very differently to full-sized particles of the same substance. And that is where a new generation of problems may be found.
As HW Longfellow’s celebrated poem about a little girl says, “When she was good, she was very very good. And when she was bad she was horrid.”
Depending on how they are made, used, handled, stored, combined with other materials and disposed of, the same is true of certain nanomaterials.
Natural and synthetic
Some nanomaterials occur naturally. Volcanic emissions are one example. Other synthetic nanomaterials have been used for decades, such as synthetic amorphous silicon used in concrete, tyres and food products.
More recently developed nanomaterials have already become commonplace. Everyday examples include nano-titanium dioxide, which has widespread uses as a UV-blocking agent in sunscreens and advanced paints.
Similarly, nano-silicon has an important part to play as an antimicrobial used in textile and medical applications. Carbon nanotubes are now found in many different products because of their combination of sheer mechanical strength, light weight, ability to dissipate heat quickly, electrical conductivity and high chemical reactivity.
As such, they appear — or do not appear — routinely in electronics, energy storage systems, spacecraft assembly, vehicle components and modern sports equipment.
At the same time, nanomaterials have the potential to burn, explode, form toxic mixes, create unintended hazardous or exothermic reactions and attack the lungs, stomach, digestive tract, liver, kidneys, heart, brain, skeleton and enter individual body cells. Some carbon nanotubes create asbestosis-like symptoms.
Although much research has been carried out into their effects, more continues. Similarly, advanced health and safety guidance is available but is being reviewed and updated.
Risk management recommends measures that err on the ultra-safe side.
Nanomaterials present a number of health and safety threats. There have been predictions of the evolution of smart and out of control “glops” that will inevitably go on to pose invisible intelligent threats to humans and the planet. Great headlines! Real risks are more objective.
One line of research is working on what nanomaterials do if they are allowed to become airborne. Another area of pressing interest is understanding much more about the mechanisms by which nanoparticles are able to enter the body through inhalation or ingestion inadvertently through the mouth or in food.
What happens when they come into direct contact with the skin is also being examined by researchers.
Airborne nanoparticles create a second threat, that of forming highly-explosive mixtures. There are also chemical risks related to fire and detonation.
The countermeasures relating to airborne risks currently centre very much around careful, correct and restricted handling, coupled with the routine use of good protective personal equipment (PPE) which includes fume hoods, facemasks and appropriate gloves.
Waste disposal and recycling is another aspect that is being considered in detail. There are currently no regulations specific to nanomaterial disposal, which is handled effectively under COSHH legislation.
However, because the manufacture of specific nanomaterials can be a very expensive process, a much greater emphasis can be expected in future on yet-to-be-developed recycling technologies designed to capture and reuse high-cost particles. This is seen as better than the alternative of allowing them to escape into the environment, where they might persist for a very long time, or simply go to waste.
In the meantime, good practice suggests that handling nanomaterials should be carried out in fully enclosed units, and preferably with the substance in question held within a solvent, or as part of a composite. Working with a dry form is not recommended.
A great deal of effort is also being put into developing inexpensive systems for the safe handling of nanomaterials. Such systems create zero air flows, use fan extraction and full filtering. A key aim is to separate the operator from the substance, while also isolating the substance from any unintended combination with other materials which could potentially react negatively given the unusual physical surface reactions of nanoparticles.
Measures taken during work in the laboratory also have to be translated into suitable systems at the engineering level, and then taken a stage further when it comes to full-scale commercial production where ordinary staff are expected to deal with new materials as a matter of course day in and day out. Training is important.
Understanding the full hazards and the consequences of exposure leads on to putting appropriate risk management controls into place.
In industrial settings, storing new nanomaterials next to oxidising agents, for example, might cause additional hazards. There is a human tendency for operators to become blasé with familiar chemicals, masking new risks. There is the additional possibility of someone inadvertently opening up the wrong valve and causing a potentially dangerous overflow.
History shows that human errors do happen despite the best intentions.
At present, there are no specific references to nanomaterials in regulations, although EU legislation on worker protection does apply.
However, the Framework Directive 89/391/EEC, the Chemical Agent Directive 98/24/EC, and Carcinogen and Mutagen Directive 2004/37/EC are relevant, as are the EU legislation on chemicals, REACH and CLP.
The European Commission has also reviewed the current position and further reading is available on types and uses of nanomaterials, including safety aspects. EU-OSHA’s publication Workplace Exposure to Nanoparticles is another informative source.
The implications for employers are that they must assess and manage the risks associated with nanomaterials in the workplace.
If the processing of nanomaterials in the environment cannot be eliminated, or catered for by substituting more acceptable materials or less hazardous processes, then a hierarchy of steps must be taken to minimise employee exposure. These are:
- technical control measures at source
- organisational measures to control risks
- PPE as a last resort.
Because many nanomaterials are relatively new, with known or suspected knowledge gaps, the onus is on both employers and employees to apply the precautionary principle and implement appropriate and adequate prevention measures.
Identifying nanomaterial emission sources and exposure levels can be difficult, more guidance and tool help can be found at the EU-OSHA website.
Additional EU-OSHA information on healthcare and maintenance work is also available, as are guidelines for specific sectors, such as the construction and furniture industries.
Another source of guidance has been developed by the UK NanoSafety Group (UKNSG) and is endorsed by the HSE.
In 2012, UKNSG published Working Safely with Nanomaterials in Research & Development as a practical guide to laboratory researchers.
The work brought together US and European information with the aim of creating uniform guidelines for the UK.
As of May 2016, the group is preparing to publish a second updated edition which includes a further literature review and more information on its initial findings.
Published by Croner-i on 30 June 2016