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Nano might be really small, but the consequences might not be

Chemical Pollution

Nano might be really small, but the consequences might not be

Published on 12 Aug 2019

If you’re really old school and print this article on a piece of paper, the paper would typically be around 100,000 nanometres thick. This is still too much to be defined as nano, however. To meet that description, most of the particles in a material need to be between 1 and 100 nanometres in any dimension. In other words, it’s very small.

What makes nano interesting, promising and worrying at the same time is the fact that nano-size particles can have very different properties from the same material when it’s made of larger particles.

The material may be made of the same chemicals and the same molecules, but the small particle size increases the surface area, which can result in special properties. The properties may also vary depending on the shape or form. Some are just irregular shapes, while others have specific forms, such as tubes or balls.

Nano-particles can be manmade (engineered) or formed by nature or by accident. Smoke, for example, contains nano-particles, and an example of nano pollution is the release of tungsten nano-particles from tire studs.

“We cannot draw conclusions on the safety of a nano material by using data from the bulk form of the chemical”

Arguably, it is very hard to say anything in general about the safety of nano. Some materials are probably safe, a few we know are very hazardous, but in general there is a huge gap in knowledge and data.

And this is exactly the main issue with nano. These materials are being used in a growing number of applications and enormous resources are being put into innovation, but so little into safety and regulation.

So what do we know? If you have a toxic chemical – it will also be toxic in its nano form. The level of toxicity can vary, as well as the mode of action. Silver is one such example, it is a biocide that becomes even more toxic in nano form.

Some materials only become problematic when they are in nano form. One reason mentioned earlier is that the size difference creates different properties.

How small is nano?

Another reason is that small particles and certain shapes are more easily taken up by the human body. Titanium dioxide in nano form can be inhaled, and once in the lungs it can trigger lung cancer. Carbon nanotubes can have asbestos-like properties, damaging lung tissue when inhaled.

This is why we cannot draw conclusions on the safety of a nano material by using data from the bulk form of the chemical.

One factor behind the lack of knowledge is that traditional test methods may not work for nano, again because the particles behave so differently.

For example, nano-particles can be very difficult to dissolve, as they stick to surfaces and are thus difficult to dose correctly. If you put them in an aquarium that contains test organisms and organic material, molecules such as proteins immediately coat the particles. The coated particles can again have different properties from the non-coated nano-particles.

However, new and more accurate tests for nano have been developed lately.

Legally, nano falls under REACH, but how REACH should tackle these materials is still under much debate. So far, ECHA and member states have been unsuccessful in their attempts to get additional data from registrants of chemicals in nano form with the motivation that the nano form may have different properties from the bulk form. The board of appeal has always overruled such requests on the grounds of lack of definitions. The definitions and characterisation further add to this being such a complex issue.

The definitions of nano and registration requirements for nano forms have been discussed in depth by the ECHA and others for many years. In November 2018, however, a REACH annex was agreed that will come into force in 2020 and will clarify aspects such as characterization, registration requirements and test methods.

At ChemSec, we are frustrated by the fact that uncertainty is so often used to slow down the regulation of chemicals. One can always find uncertainties, and thereby delay decisions.

When it comes to nano materials there is definitely no lack of uncertainty. But instead of being paralysed by the things we do not know, we should act on the things we do know – and we must take a precautionary approach. I believe three things are urgently needed:

  • There needs to be transparency on nano. Production, processes, volumes and products should be registered.
  • Specific safety data should be required for nano forms, with realistic testing of hazardous properties for human health and the environment.
  • In the case of the few nano forms that have been around for a long time, for which data exists showing they are of high concern, they should be regulated ASAP.

Dr. Anna Lennquist
Senior Toxicologist