The simplest way to define nanomaterials is “anything that comes in a particle size between 1 and 100 nanometres”.
Nano-particles can be man-made (engineered) or formed by nature or by accident. Engineered nanoforms are legally covered by REACH, but the implementation has been slow since the definition and registration requirements have been discussed for many years. In November 2018, however, a REACH annex was agreed (that will come into force in 2020) that clarified aspects such as characterisation, registration requirements and test methods.
The next step, to identify the first nanomaterial as a Substance of Very High Concern (SVHC) is likely to follow.
What makes nano special is that nano-sized particles can have very different properties compared to the same material made of larger particles. This is what makes it so interesting from an innovation point of view. But also why it is not possible to draw certain conclusions about the safety of nanomaterials from what we know about the “bulk” form of a chemical or material.
We cannot say that nanomaterials are inherently hazardous, just because of their nano size. However, there is a great lack of knowledge and data regarding hazardous properties of nanomaterials. This raises uncertainty among users and consumers regarding the safety of nanomaterials.
When there’s a lack of data, precaution is a reasonable way forward.
However, one of the more well-studied nanomaterials is carbon nanotubes. First engineered in the 1990s, carbon nanotubes have since then been regarded as a very promising material. Not all promises have been fulfilled, but they are used to make durable, lightweight materials, for electrical conductivity, as a super-black pigment and for water purification, among other things.
Several studies have shown that carbon nanotubes cause lung cancer. The small tubes induce inflammation in a somewhat similar way to asbestos. The international agency for cancer research, IARC, has classified a certain type of carbon nanotubes as carcinogenic.
In other studies, reprotoxic properties have also been observed. It is also known that carbon nanotubes do not degrade in natural environments, thus they are persistent.
There are many different forms of Carbon Nanotubes (CNTs). They can be Single Walled (SWCNTs), Double Walled (DWCNTs) or Multiwalled (MWCNTs). They can be tangled, longer or shorter.
The production process often renders a mix of different forms of carbon nanotubes and catalysts. There are various methods to purify nanotubes, but it is complicated and expensive to get a clean product.
In 2019, ChemSec added carbon nanotubes to the SIN List because they are carcinogenic, persistent and probably toxic to reproduction.