The little things matter

Use of nanomaterials is growing, but regulations controlling their impacts are lagging behind. John Barwise reports

The use of nanomaterials dates back to ancient times when Egyptians introduced lead sulphide nanocrystals to the manufacturing of hair dies. The famous Roman Lycurgus glass cup, which changes colour as light passes through it, does so because it contains nanoparticles of a silver-gold alloy. German studies of Damascus swords dating back to the eighth century AD reveal nanowires and nano-sized tubes running through the steel blade, which give the swords their legendary strength and sharpness.

Nanomaterials have been used on an industrial scale for many years. Carbon black is used as filler in the manufacture of rubber tyres because of its high surface to volume ratio. Amorphous silica is commonly used in semiconductor circuits and, because of its dielectric strength and mechanical resistance, it has become a key material in microelectronics and chromatography.

But it is only in the last 30 years, that nanoscience and nanotechnology have advanced to a level where it is now possible to manipulate atoms and molecules and intentionally modify their structures to engineer a whole new suite of designer nanomaterials, tailored to suit a growing demand for new materials.

Nanotechnology is the fresh frontier of science.

Size matters

Nano is derived from the Greek “nanos”, meaning dwarf. A nanometre is one billionth of a metre or 10-9 and is used to measure dimensions at the atomic scale.

To put this in perspective, a strand of human DNA is 2.5 nanometres and a sheet of paper is about 100,000 nanometres thick. At this scale, atoms and molecules can exhibit unique properties and characteristics. Using surface area as an example, a 1cm cube of material dissected into single nanometre cubes increases the total combined surface area 10 million times.

Nanoscale structures exist in the natural world as atoms and molecules. Solids, liquids and gases exhibit different chemical, biological and physical properties at the nanoscale than the more conventional-sized materials with which they are associated. Surface areas per unit of mass increases, surface charge and chemical reactivity can change and electronic characteristics can be modified.

Recent advances in electron microscopy and other technologies, has enabled scientists to determine the position of atoms and molecules in materials and observe structures and processes at a scale never previously observed. Nanoscience is about understanding how these structures work and finding ways to control their natural properties. This in turn has helped to develop a whole new toolkit to characterise and catalogue nanomaterials for potential use.

Nanotechnology uses these applications to restructure, manipulate and exploit matter at the atomic and molecular scale to create new products with tailored characteristics and complex functional devices. Structured nanoparticles can be engineered to produce materials that are stronger, more magnetic or better at conducting heat and electricity than other forms of the same material. Graphene, an incredibly strong, flat layer of carbon obtained through a micro-mechanical process, is a good example.

Mega products

Nanoscience and nanotechnologies are developing at a rapid pace and their application in engineering and manufacturing is also growing. Types of nanomaterials already on the market include nanoparticles, porous materials, nanofibres, fullerenes and graphene (carbon), nanocoatings and composites.

According to data published in 2012 by the project on emerging nanotechnologies (PEN) at the Woodrow Wilson international centre in the US, more than 1,300 nanotechnology-enabled products have entered the commercial marketplace around the world. This is a significant increase on PEN’s 2006 inventory of just 200 products and reflects the continuing growth of nanomaterials.

Product lines that dominate the market include health and fitness items, representing 56% of the product list. Nearly a quarter (24%) of the inventory includes nanoscale silver, which is used for its antimicrobial properties in medical products.

But the potential for expanding the use of nanomaterials in products is huge. Research by investment analysts Lux indicates that the markets where nanotechnology is already being incorporated into products are worth $254 billion worldwide, and they are projected to grow to more than $3 trillion by 2020.

About 15% of global manufacturing output will incorporate nanotechnology by 2014.

Into the unknown

Engineered nanoparticles are novel and do not usually appear in nature. But because of their unique properties they can penetrate animal and plant cells when released into the environment.

Research into nanotoxicology and the risks to human health and the environment is still in its infancy, but earlier research into vehicle exhaust gases suggests there may be cause for concern.

Diesel combustion releases diesel particulate matter, containing soot and aerosols of silicates and other particulates in the sub-100 micrometre range. Short-term exposure to these exhaust gases causes headaches, eye irritation and breathing difficulties, while in the long term they can lead to cardiovascular disease and lung cancer.

A more recent animal study undertaken by the Marshall centre for diagnostic nanosystems indicates that the diesel additive cerium oxide – a nanoparticle – can circulate from the lungs to the liver, which can lead to liver damage.

Cerium oxide additives were introduced to improve diesel fuel efficiency and, ironically, cerium is also used in catalytic converters to reduce nitrous oxides from vehicle exhausts and convert harmful carbon monoxide to the less harmful CO2. “The potential effects of nanomaterials on the environment and cellular function are not yet well understood,” confirms Siva Nalabotu, the study’s lead author.

The potential for negative as well as positive impacts of nanomaterials is a major challenge for the industry. Carbon nanotubes (CNTs) are the star attraction in the nanomaterials engineering league. Characterised as single or multi-walled nanotubes, CNTs are in demand because of their extraordinary thermal and electrical conductivity, and their mechanical properties. Engineered CNTs are 60 times stronger than steel yet six times lighter and are used in a wide range of electronics, optics, sports equipment and household goods.

However, exposure to CNTs can be extremely hazardous. The thin needle-like structure has been likened to asbestos and animal experiments suggest inhalation may be capable of manifesting asbestos-like pathogenic effects. Research carried out on mice has found that exposure to long, multi-walled CNTs resulted in lesions similar to those caused by asbestos.

The occupational use of nanomaterials is regulated under the Control of Substances Hazardous to Health (COSHH) regime but, according to guidance from the Health and Safety Executive (HSE), the toxicity of CNTs has not been fully investigated and the problems of measuring airborne exposure levels make it difficult to carry out a rigorous COSHH risk assessment. Further research into environmental exposure and inhalation is ongoing.

Silver nanoparticles have anti-microbial properties and are produced in large volumes for use in a wide range of applications from medical dressings, cosmetics, fabrics and toothbrushes through to washing machine disinfectants.

The toxicological effects of nanosilver are largely unknown and, in 2009, Defra asked the advisory committee on hazardous substances for guidance. The committee’s report indicated that there is likely to be wide exposure to low concentrations of nanosilver, but that it is not possible to rationalise the disparate (eco)toxicology results.

The report recommended that given these uncertainties further knowledge on both the hazard and exposure to it is urgently required. More recent monitoring of nanosilver at nine sewage treatment works by the centre for ecology and hydrology (CEH), concluded that predicted river concentrations are below levels where acute harmful effects on wildlife might be expected. The fate of engineered nanomaterials is perhaps the most important and yet least understood aspect of nanoscience and technology.

CEH is one of the lead bodies in NanoFATE, a new EU-funded collaborative project based in the UK and involving 12 partners from nine European countries. Its remit is to re-evaluate risk assessment methodologies and improve safety assessment of engineered nanoparticles. It will examine post-production life cycles of key nanoparticles from their entry into the environment, including waste treatment processes, and investigate the fate and effects of engineered particles.

Regulating matter

Despite the wide-scale manufacture and distribution of products containing nanomaterials, the regulatory framework for processing, producing, managing, using and disposing of these materials is neither clear nor comprehensive.

It was not until October 2011 that the European Commission finally published a legal definition of nanomaterials to be used for regulatory purposes and which will also act as a common reference for various other commission provisions.

While the definition provides a regulatory framework, it is based only on the size of the constituent nanoparticles and does not cover the more pressing issues of health-and-safety risks or environmental hazard presented by the materials themselves. Instead, the commission is relying on its REACH Regulation (1907/2006) and other existing regulations to manage these aspects.

REACH – the registration, evaluation, authorisation and restriction of chemicals – entered into force on 1 June 2007 and requires manufacturers and importers of chemicals to register them with the European Chemicals Agency (ECHA) and provide data on the substance in a dossier.

There are no provisions in REACH that refer explicitly to nanomaterials, although they are covered by the “substance” definition in REACH. Under REACH, registration dossiers are only required for substances that are manufactured or imported in fairly large quantities, such as 100 tonnes a year. For most companies importing or manufacturing nanomaterials the amounts they use will be significantly less than this and so they will operate under the REACH radar, unless the materials are classified as hazardous in which case the ECHA must be notified.

A 2012 report from the centre for international environmental law, entitled Just out of REACH, argues, for example, that most nanomaterials will evade REACH registration until 2018, and that with the REACH schedule for registration hinging on the amount of a chemical, it essentially misses most nanomaterials, because they are generally produced in small quantities.

Author of the report, David Azoulay, says: “Three years ago, the commission declared that REACH theoretically covered nanomaterials; but they continue to enter the EU market with little or no information on their potential risks, violating REACH’s ‘no data, no market’ principle. The problem is that the regulation contains legal gaps and shortcomings that render it completely ineffective for nanomaterials.”

The ECHA can request information on a substance independent of the minimum requirements of REACH and in March 2012 issued new guidance for registering nanomaterials. The guidance aims to help registrants on the adequacy of test methods, for example, but the risk element is limited by the lack of existing comprehensive toxicological data for a range of nanomaterials.

The Helsinki-based regulator accepts the commission’s core definition of nanomaterials, but its own assessment of REACH registration dossiers indicates that the scope of registration is unclear and nano-specific information in terms of substance characterisation, hazards, exposure and risks shows “significant room for improvement”.

The agency is now seeking a common approach with competent authorities in member states, such as the HSE in the UK, taking into account scientific uncertainties and the REACH legislative framework.

In October 2012, the commission announced that it is considering amending some of the annexes to REACH to clarify how nanomaterials are addressed and safety demonstrated in substance registrations.

“REACH sets the best possible framework for the risk management of nanomaterials when they occur as substances or mixtures, but more specific requirements for nanomaterials within the framework have proven necessary,” said the commission. Fundamentally, it confirmed that EU legislation does not need a radical overhaul because there is still a “considerable lack of data on exposure to nanomaterials”.

In the UK

To some extent, individual member states will have to rely on their own governments and agencies to regulate nanomaterials.

Both Defra and the business department (BIS) are leading the UK’s contribution to international research and development. A new nanotechnologies collaboration group will facilitate coordinated research and explore industry reporting schemes, and a new public information website has been launched.

Defra’s primary aim is about understanding the impacts of nanomaterials and controlling their impact on human health and the environment, but there is still a lot of work to do.

Steve Morgan, from the chemicals and emerging technologies team at the environment department, explains: “It is important to bear in mind that the knowledge base on the fate and behaviour of nanomaterials is currently lacking and the methodologies required to enable an effective risk management response are not yet available.”

Defra’s plan is for a life-cycle approach to be taken when considering the risks posed by such materials, so that the implications of exposure throughout manufacture, use and disposal is assessed. At present, companies do not have a legal duty to report their use of nanomaterials and the range of processes and products currently in operation or under development in the UK is limited.

The environment department’s industry-wide voluntary reporting scheme (VRS), initiated in 2006 to track engineered nanomaterials, attracted few participants and was scrapped.

The Environment Agency is currently working to fill the gap left by the VRS, inviting businesses to take part in another voluntary assessment of the production and use of nanomaterials. The project has been widely publicised through the Knowledge Transfer Network (KTN) and is ongoing.

The agency has also classified unbound CNTs in waste materials as hazardous waste because of their harmful properties. But with so little information about the products and pathways, trying to monitor and regulate all CNT waste arisings and disposal may be a challenge.

Elsewhere in Europe, research is ongoing. Denmark’s nanoscience centre is involved in technology transfer studies, for example, and Germany’s federal environment agency is studying the fate of some nanomaterials in the environment. France, meanwhile, will require manufacturers, importers, and distributors of nanosubstances to submit annual declarations of information from 1 July 2013.

At the industry level, ISO technical committee TC 229 is dedicated to developing standards for nanotechnologies. The committee has published 23 specifications and technical reports since 2008, and is currently working on another 15, including ISO/DTS 12901-2, which focuses on applying occupational risk management to engineered nanomaterials.

Up, up and away

To date, governments around the world have invested more than $67 billion in nanotechnology, and corporate investment in manufacturing infrastructures, new nanomaterial product lines and technology transfer is also growing. PEN estimates that if the current growth trend continues, the number of nano-based products could reach 3,300 by 2020 and could expand rapidly after that.

“The use of nanotechnology in consumer products continues to grow on a rapid and consistent basis,” says PEN director David Rejeski.

Yet, there are few national regulations or international agreements in place to monitor and control nanomaterials across their life cycles and governments are reluctant to introduce new regulations until nanomaterial pathways and outcomes are more clearly defined and the risks better understood. That is likely to take several years, however.

Meanwhile, pioneering work to develop new nanomaterials continues apace. One case study highlighted in the BIS strategy document shows how nanotechnology could be used to produce food alternatives to replace fats in ice cream.

Will this require new food regulations – and what about the waste arisings? Like the rest of us, the regulators may just have to suck it and see.