Nanomaterials are being used in an increasingly diverse range of products, but what if any, are the potential health implications of working with the substances?
Nanomaterials are interesting for many applications in the construction, textiles, and energy industries; however, reducing the size of a material into nanometre dimensions often strongly changes the properties of the material.
As an example, regular titanium dioxide (TiO2) is an inert, nontoxic white substance used as paint and food colorant. Its nano-form, however, is an invisible catalyser that can destroy air pollutants such as diesel soot, which makes it a very interesting additive for self-cleaning paints, mortars and other cement-based products. Nano-TiO2 is also used to produce novel, very cheap solar panels.
Another ‘magical’ substance comes in the form of carbon nanotubes, which are many times stronger than steel. They are so strong that carbon nanotube reinforced concrete no longer requires steel bars. Its weaker cousin – nanofibres made of polymers – is great for filters and textiles because tissues woven with nanofibres retain solids and even liquids, while air and vapours can pass easily. They are thus promising for waterproof breathable textiles and are also being tested for respiratory protective masks.
The Middle East is a region with a booming construction industry. Some initial construction projects already use self-cleaning mortar. Our own market survey suggests that ultra-strong, nanotube-reinforced concrete has not yet reached the markets, although we cannot exclude that tests are already done with such concrete types.
Another important field where nanomaterials are already frequently being used is the textile industry. Many products use nanocoatings on fabrics: these are very thin layers of water-repellent substances that form nano-structures to make the material super hydrophobic. Another important use is nano-silver in textiles and also in plastics, which makes these products’ surfaces bactericidal.
The fact that nanomaterials have new functionalities and properties has implications for the risk assessment: it has to be re-done, because nanomaterials have a different toxicological and exposure profile than their regular counterparts. Fortunately, most of the known nanomaterials are not extremely toxic and can be safely used, as long as human exposure is kept at a reasonable level. Some nanofibres, however, are viewed more critically: laboratory animals exposed to so called biopersistent high aspect ratio nanomaterials (HARN) developed asbestos-like diseases. It is thus important that producers avoid making products that can release even small numbers of such dangerous long biopersistent fibres, and to use whenever possible short and biodegradable fibres.
To understand how to protect workers we have to understand the important uptake routes. The lungs are an especially good entry portal for nanomaterials. Nanoparticles and their agglomerates are very fine airborne particles and can get easily inhaled. Once inhaled, nano-scaled objects can, to a small extent, translocate into the human body. While the skin is not a good entry portal, substances that cause direct skin effects should not be neglected. Finally, particles taken up through the gastro-intestinal tract can also translocate into the body, but not as much as through the lungs. Fortunately, involuntary oral uptake is rare in occupational settings as long as the concept of not having any type of food or beverages inside production halls is respected.
The lungs are not only the most important uptake route in occupational settings, they are also the largest target for hazardous substances reaching humans via the air. The surface of the lungs is about the size of a tennis court, a much larger surface than any other organ with contact to the outside world. Particles that are smaller than a few micrometres in size are sufficiently small enough to be inhaled deep into the alveolar region of the lungs. The alveolar region consists of small air pockets whose walls are covered by many small capillary blood vessels. This is the air-exchange region where oxygen diffuses into the blood and carbon dioxide is released into the air. It is thus a very sensitive zone and needs appropriate protection, because chronic particle exposure can damage the lungs and lead to heart tissue death, stroke and cancer. It is very important to protect the lungs from nanomaterials. Recommended exposure limits (REL) for nanomaterials are much stricter than the regular material’s counterpart. For example, nano-TiO2 has a REL of 300 µg/m 3 , as compared to 3 mg/m 3 for regular TiO2.
Current guidance for safe work with nanomaterials focuses on safe handling and control of exposure. These are two central principles for managing the potential risks to health from nanomaterials. The general approach towards safe handling and control of nanomaterials is similar to that for other hazardous substances, which is reflected in the UK’s Control of Substances Hazardous to Health Regulation (COSHH).
One needs to:
• Identify the hazards and assess the risks • Identify the precautions that are needed • Prevent or adequately control exposure • Ensure that control measures are used and maintained • Monitor the exposure • Carry out appropriate health surveillance • Prepare plans and procedures to deal with accidents, incidents and emergencies • Ensure employees are properly informed, trained and supervised
Technical and organisational measures are the most important elements for preventing exposure to nanomaterials. Personal protective equipment (PPE) is used when the exposure to a person is either too high or if there is a reasonable chance that a person could get exposed. Whenever possible, however, PPE should not be used as the first line of defence. Instead, organisational and technical measures are preferred. We can compare the approach to dangerous nanomaterials to the approach that one would take to maintaining a tiger in a zoo. A well-organised and equipped zoo will feed the tiger with a system where either the food is placed inside the cage while the tiger is not there (organisational), or they will use a flap (technical) to insert the meat into the cage. Rarely would you see somebody walk inside with a load of meat, wearing a knight’s armour. There may still be cases where somebody has to go inside, such as medical treatment of the tiger. In that case, however, you would sedate the animal and have the vet accompanied by an animal trainer, just in case. In the same way, PPE should be seen as the second line of defence, so gloves should be worn to protect against spills, not to dip the hands in a liquid; and filter masks should protect against accidental releases of powders, whereas routine work should be done in an atmosphere with low dust concentrations.
Working with HARN
Working with biopersistent high aspect ratio nanomaterials (HARN) such as long carbon nanotubes is an area of specific concern.
The Health and Safety Executive (HSE) in the UK defines HARN of concern as having all of the following characteristics:
• One dimension in the nano-range • Longer than 10–20 µm • Biopersistent • Do not dissolve or break into shorter fibres
The concern is that these may be retained within the narrow space surrounding the lungs – the ‘pleural cavity’ – for long periods. 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. It should be noted that fibres that are thicker than 100nm, but that have otherwise the same properties, are also health concerns; they are just no longer defined as being nanomaterials.
How can you stay healthy when working with HARN? First, it is important to always ask an EHS-expert to check and approve newly set up workplaces and work procedures. One should work with HARN only in approved high safety zones and avoid procedures that can create dust or liquid aerosols. It is also important to be meticulous when cleaning the workplace (and wear protective gear for doing it) so that no HARN stay behind after the work is completed.
In view of the existing concern and uncertainty regarding nanomaterials exposure of workers, an understanding of release and the control of emissions is essential for informed risk assessments. For this purpose, the Institute of Occupational Medicine (IOM), together with leading institutes worldwide, tested and successfully uses state-of-the-art portable instrumentation for the detection and characterisation of airborne particulates that can pose an exposure risk.
These techniques nowadays allow to identify and help control exposure in the workplace through:
• Real-time characterisation of particle release from the handling, manufacture and finishing of nanomaterial products and articles • Background monitoring to discriminate between natural and process-related emissions • Assessing the persistence of nanomaterials in the air • Personal and area sampling of airborne particles, with offline gravimetric, imaging, and/or chemical analysis • Evaluation of control measures, especially testing the efficiency of filters to retain nanoparticles • Comprehensive analysis, interpretation and best practice recommendations
Besides exposure assessment, it is also important to evaluate the hazards posed by nanomaterials and products containing them. Today there is already good knowledge and expertise of strategies and methods to provide the necessary hazard information needed to safely develop and market materials and nanotechnology-enabled products that meet the increasing number of regulatory requirements.
It is against this backdrop that I and IOM Singapore aimed to create a new training course to provide people with the knowledge to work safely with nanomaterials in laboratories. I received funding from the Institution of Occupational Safety and Health to create the course and wanted to give laboratory staff, students and safety and health professionals at universities and other research and development facilities a good understanding of approaches towards safe and healthy working in labs where nanomaterials are used or produced.
The newly developed IOSH-accredited course targets two key populations. The first is the researchers and technicians working in laboratories with nanomaterials. These people need to understand the protection needs, what technical and organisational measures this implies, and how to locate and correctly wear PPE. In addition, they need practical guidance on how to specifically do their daily lab routines in a safe and health way. Secondly, it targets safety and health staff who need to carry out risk assessments and provide EHS support to researchers working with nanomaterials. They have to understand the protection needs and how this can be implemented, including practical tips on how to organise the necessary technical and organisational measures and how to make sure the staff has access to the appropriate PPE. In addition, they need to understand where researchers have insufficient knowledge or poor understanding of EHS concepts.
The newly developed training addresses these needs with a dual structure of classroom teaching combined with practical exercises. The first half day, participants learn in a classroom the basics through lectures and interactive learning. The second half of the course day is done in real labs where participants learn hands-on how to do typical manipulations in a safe and efficient manner. The tasks chosen to practice good ways to stay safe and healthy are those frequently encountered in labs, such as weighing powders, mixing liquids, cleaning spills and more. The course also provides guidance on how nano-lab safety can be achieved by smart planning of experiments.
The first courses provided were attended by researchers, health and safety staff of leading universities, and governmental officials and work inspectors. They gave the course and the trainers a very high rating and were very appreciative of what they learnt in the course. The course is currently run twice per year in Singapore and in the UK. In addition, it can be provided to universities, companies and governments around the world who wish to train their staff and experts on safe work with nanomaterials. For more information or to order such tailored training, contact [email protected]
There are several websites that provide information about safety and health aspects of nanomaterials. We especially recommend that you visit www.safenano.org, IOM’s internet guide to high quality recommendations on occupational practices. It provides a rapid overview of all aspects necessary to stay safe and healthy. It not only showcases IOM’s own research findings, but also compiles the best information from the web in a pre-digested format. For information regarding all other aspects of health and safety, we recommend readers to look at www.iosh.co.uk.
Published: 15th Dec 2015 in Health and Safety Middle East