Nanomaterials: a new threat to the recycling industry?

A large variety of nanomaterials is used in consumer products and industrial applications, and many of these products have reached the end of their life. However, studies have shown that various types of nanomaterials cause toxic effects, which makes the development of appropriate recycling strategies imperative.

By Lydia Heida

‘Every 18 months, we see a doubling in consumer products that claim to contain nanomaterials in Europe,’ says Steffen Foss Hansen, associate professor at the Technical University of Denmark and co-founder of The Nanodatabase, which was set up in 2012.

Carbon nanotubes are used in electronics, batteries, sporting goods, composite plastics, concrete and ceramics. Nano-titanium dioxide is used in an equally varied amount of products: paints, coatings, building materials, textiles, electronics and metals, whereas nano-silver is mostly used in textiles, kitchenware and coatings.

The global nanomaterials market is expected to exceed US$ 55 billion by 2022 from US$ 14.7 billion in 2015, according to a report of Allied Market Research. The largest application for nanotechnology is electronics, followed by energy applications.

Many of these materials and products have already reached their end of life. So the development of appropriate waste management strategies is critical, according to a report of the Organisation for Economic Co-operation and Development (OECD) about waste containing nanomaterials, that was published in 2016.

This is especially important since more than 11 million tonnes of nanomaterials are entering the market a year. But this number is a rough estimate according to several experts.

‘There is a lack of access to information about how much nanomaterials are produced, how much is used, by whom, and wherein,’ explains Hansen. ‘We have been calling for regulation for a long time in this area, as any kind of risk assessment starts with knowing what is out there.’

Serious risks

Most nanomaterials are based on metals that are shrunken to a molecular scale: one nanometer is one billionth of a meter, which is 10 000 times smaller than the diameter of a human hair. At this scale, the material is no longer seen as a metal, but as a chemical that may have novel properties compared to their bulk form.

That is also the reason why nanomaterials have become so popular to use. Wind turbine blades with a coating that contains carbon nanotubes produce 30% more wind power than conventional blades. Nano-silver acts as an anti-bacterial agent in textiles, but this function makes these particles also deadly to micro-organisms in the soil.

Studies have shown that various types of nanomaterials cause toxic effects not induced by their chemically similar but larger particles, such as inflammation or fibrosis of the lungs or cancer as an analogy of the carcinogenicity of asbestos.

Other adverse health effects: interfering with the ability to reproduce, toxic effects on the liver, kidney and nervous system, cell death, chromosomal aberrations and DNA damage.

The extremely small size of nanomaterials makes it possible that they penetrate parts of the body that are not reachable by larger particles.

‘Nanomaterials tend to be much more reactive, because they have much more surface area per unit volume than larger particles,’ explains Kai Savolainen, research professor at the Finnish Institute of Occupational Health and the coordinator of Nanosolutions, a project that was created to develop a safety classification for nanomaterials, to which 500 scientists contributed worldwide.

Also, the extremely small size of nanomaterials makes it possible that they penetrate parts of the body that are not reachable by their larger counterparts, such as the alveoli in the lungs. Nanomaterials can transfer through the lymphatics and blood into internal organs, and are able to pass the blood-brain barrier.

Some nanomaterials surface often in toxicity studies, such as carbon nanotubes, nano-silver, nano-copper oxide, nano-cobalt, nano-cadmium and nano-titanium dioxide. But experts agree that much more research is needed about the effects of nanomaterials on human health and the environment.

Dust explosions

At the moment, waste containing nanomaterials is recycled along with conventional waste, with no special precautions. Recycling facilities simply don’t know which end-of-life products or materials contain nanomaterials and guidelines have not yet been developed.

During recycling processes, nanoparticles might be released into the workplace atmosphere or emitted into the environment, according to the OECD. Furthermore, unknowingly storing or processing waste with nanomaterials increases the risk of dust explosions. Nanoparticles might also end up in recycled materials.

‘For the moment, we don’t know enough about risk and exposure, so there is not a sufficient scientific basis to undertake action,’ says Peter Börkey, team lead circular economy at the OECD.

Worldwide regulations

Recently, the first steps have been taken to regulate the use of nanomaterials worldwide, which may lay the foundation for proper guidelines to recycle waste containing these materials. Since 2017, the U.S. Environmental Protection Agency (EPA) requires information about manufactured, imported or processed nanomaterials.

New chemical substances manufactured at the nanoscale must be submitted to EPA for review before they can enter the market, according to Tricia Lynn, spokesperson of EPA.

In Australia, the existing regulatory framework for chemicals will be reformed, to cover the registration of nanomaterials. Canada is developing a risk assessment framework for nanomaterials in commerce. This year, experts are consulted about the draft of this framework.

Taiwan has set up a verification system, named nanoMark, to classify, certify and regulate products that claim to make use of nanotechnology or nanomaterials, as some of these claims have been proven false.

‘Several experts name France as the leading country worldwide, where it comes to the registration of nanomaterials.’

Thailand has developed a similar system: the NanoQ label. This voluntary scheme might be expanded to imported raw nanomaterials.

Several experts name France as the leading country worldwide, where it comes to the registration of nanomaterials. In 2012, it was the first country to adopt a mandatory reporting scheme for produced, imported or distributed nanomaterials in quantities above 100 grams per year.

Around 2,600 companies have made 14,000 registrations of 300 different nanomaterials, which equals a volume of about 500,000 tons. Carbon black, nano-silicon dioxide, nano-calcium carbonate and nanotitanium dioxide take up around 35% of this amount. About 65% of registrations were for nanomaterials produced or imported in volumes of less than 1 ton.

Other European countries that have set up a registration system for nanomaterials or products containing nanomaterials are, for example, Belgium, Denmark, Norway and Sweden.

REACH amendments

The European Union is planning to make large strides regarding the registration of nanomaterials. Just before the summer, EU member states reached an agreement on proposed amendments to clarify REACH registration requirements with regard to nanomaterials.

From January 2020, it will be mandatory for companies to give information about basic characteristics of produced or imported nanomaterials, what risks they might pose to human health and the environment and how to use them safely, among others.

‘We are quite happy with those amendments,’ says Gregory Moore, scientific officer at the Swedish Chemicals Agency. ‘More information needs to be given about the properties of nanomaterials. For example, about the shape and size of a nanomaterial and whether it bio-accumulates in the body.’

‘But some member states, including Sweden, would have preferred mandatory registration for nanomaterials that are produced or imported in quantities of 100 kilograms or more per year as many come in very small quantities. Currently, it is set at 1 ton or more per year.’

Another point of critique is that still nothing will be known about which products and materials contain these nanomaterials. This information is necessary to develop guidelines for recycling and other forms of waste management.

Impacts for workers

In the past years, a few dozen studies have examined the release of nanomaterials during recycling processes. Some studies show that during shredding and re-granulation of PET-bottles nano-titanium dioxide and carbon nanotubes are released, but other studies provided dissimilar results.

Another study indicated that waste tires are a problematic waste stream as they contain different types of nanomaterials. The recycling of construction and demolition waste has also been studied, and this showed that nanomaterials may become airborne during crushing, shredding and milling.

‘The most serious risks is to workers,’ says Börkey. ‘These risks can be mitigated through classic workplace security measures, such as wearing masks and ventilation systems that clean the air in a factory. But in emerging countries, like India and China, those standards are often not upheld and they take in a lot of our waste.’

‘In emerging countries, like India and China, workplace security standards are often not upheld and they take in a lot of our waste.’

One of the latest research projects seems to confirm this viewpoint. The German project ProCycle investigated the toxicological risks of dust emissions that occur during the recycling of plastic nanocomposites, among others.

‘Grinding of nanocomposites resulted in a lot of particles that were too large to penetrate the alveoli of the lungs, whereas a small amount of material changed into the gaseous state,’ says Eric Marioth, research coordinator at the Fraunhofer Institute for Chemical Technology, which is participating in ProCycle.

‘We have monitored the deposition of dust and aerosols on different cell media, such as artificial lung cells, to look for stress indicators in cells. These effects mostly occur by gaseous substances, and that might have an effect on health,’ according to Marioth.

His preliminary conclusion would be that ‘the current health and safety regulations for recycling facilities in the EU should be sufficient to mitigate these risks.’ The project has ended in September and early 2019 a workshop will take place to discuss the final results with stakeholders in the recycling industry, among others.

Recycled materials

Even fewer studies have been dedicated to the presence of nanomaterials in recycled materials. One study concluded that ‘less than 10% of nanomaterials from different products will be recycled back to the production and manufacturing chain.’

Another study predicted that ‘about 40-47% of nanomaterials in construction materials ends up in recycled materials.’ ‘We still know far too little even of the production of nanomaterials, and their use,’ comments Börkey. ‘It is a big leap forward to look all the way into the end-of-life of products containing nanomaterials. And then to the use of secondary materials.’

‘I think that the problem with nanomaterials is similar to the issues with other hazardous substances, such as flame-retardants, that have found their way into recycled materials. These recycled materials are applied in products that result in significant exposure. For example, plastic toys that are imported from China.’ But, again, much more studies are needed to confirm this hypothesis.

Release into the environment

The release of nanomaterials into the environment surrounding recycling facilities is also an issue that hardly has been studied worldwide. However, the H2020 project NanoFASE, that runs for four years until August 2019, will change this.

‘The project is still in progress and major findings and reports are due to come out in the next year,’ says Lee Walker, who manages this project on behalf of the UK Natural Environment Research Council.

‘We are conducting modeling exercises to see whether nanoparticles stay embedded in products or are released in the environment at some point. Size is a factor, but also what a nanoparticle is composed of. Some materials are more soluble than others.’

‘They can be transformed as well. For example, nano-silver has a tendency to be sulfurized during waste management processes which slows down the dissolution of these particles,’ explains Walker.

‘Other parameters are the surface chemistry of the compound and how they are embedded in the product, because that also might determine their release.’ The project is intended to support REACH regulation.

Walker: ‘Within the NanoFASE framework, there will be a guide to generate parameters and model those parameters, to enable companies to complete the registration of nanomaterials within REACH.’


The next step would be to monitor the release of nanoparticles in real recycling plants, instead of modeling these effects in laboratories, according to Florian Part, senior scientist at the University of Natural Resources and Life Sciences in Vienna and coorganizer of the Task Group on Engineered Nanomaterials in Waste.

In 2014, the International Waste Working Group formed this task group to respond to the emerging challenge that nanomaterials form to waste managers. Its aim is to develop proper guidelines for end-of-life management strategies for waste that contain these materials.

For real-life monitoring tests, Part would prefer a plant that recycles e-waste, plastic or construction materials. He estimates that ‘it would take at least three to four years to conduct tests.’

‘If producers whistle-blow information about materials, it could be the basis for design-to-recycle and risk assessments.’

‘The first two years, you have to establish a method and adapt your equipment to the circumstances in a plant. You also have to develop new protocols for sampling, because standard protocols are not applicable to nanomaterials, and new instruments since nanoparticles are too small for many instruments.’

‘It will be necessary to work together with many different experts from various fields to execute tests, such as engineers, environmental chemists, analytical chemists and toxicologists. The budget needed would be around 1 million euro,’ estimates Part.

He adds: ‘In environmental chemistry and waste management, we are used to dealing with substances that have been brought onto the market years or decades before. It would be great if producers whistle-blow in-depth information about material and elemental compositions. This would be the basis for design-to-recycle concepts, as well as for risk assessments.’

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Nanomaterials: a new threat to the recycling industry?

Published: November 2018 in Recycling International.

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