Graphene was discovered relatively recently. While everyone agrees on its incredible properties and the possibilities it brings to industry in particular, more and more studies are also aiming to assess graphene’s toxicity on human health.
This issue is attracting growing interest, including from the general public, particularly since the health crisis of 2020-2021, when graphene-based surgical masks were introduced and then withdrawn from the market in view of their potential health risk.
In this article, Carbon Waters presents the results of several studies into the safety of graphene, carried out by:
- A multidisciplinary team from the Graphene Flagship (the Health and Environment Work Package) and independent partners
- The National University of Singapore
- The Royal Society of Chemistry and the Graphene Council
- The Strasbourg Laboratory – CNRS Immunology
There is not one but many graphenes
First of all, it’s important to mention that the term “graphene” is generally used to describe all 2D nano-carbon materials. However, this is a family of materials whose components differ in thickness (number of layers), quality, stability and purity.
This family also includes more or less oxidized graphenes such as graphene oxides (GO) and reduced graphene oxides (rGO). These differences are a direct consequence of the production process.
What’s more, they are available in a variety of forms: in powder, pre-dispersed in liquid products, in paste form, as a masterbatch or as a film on a metal plate, and so on.
Source: the Graphene Flaghsip
Most of the above-mentioned studies have been carried out on graphene oxide (GO), via in vitro and in vivo modeling and testing.
Studies on the cytotoxicity of graphene:
the main results
Results differ from one graphene to another,
depending on its quality
The existence of different forms of graphene has led to different results regarding its safety. Indeed, from one study to the next, scientists have based their research on one type of graphene or another.
Take, for example, the study by the University of Singapore (Cytotoxicity survey of commercial graphene materials from worldwide, 2022) carried out on 36 types of graphene available on the market.
Antonio H. Castro Neto points out that “the toxicity of graphene, besides its dose, is not due to graphene itself but to the impurities that are a sub-product of graphene’s industrial processing”.
He adds: “Our study suggests that over 35% of the graphene products contain highly defective graphene; we observed the presence of organic and/or inorganic impurities in almost all the samples. Our results prompt the conclusion that a product’s cytotoxicity cannot be related to any characteristic of graphene alone, but it is determined by the contaminants present.”
Exposure level and concentration also play
a role in graphene toxicity
Studies show that the exposure factor (form, duration, quantity) has a direct impact on graphene’s health risks.
For the Royal Society of Chemistry (RCS) and the Graphene Council, if graphene is integrated within a matrix, it presents no greater health and safety risk than any other material. According to the RCS, “once a nanomaterial (including graphene) has been incorporated into a product, it is virtually impossible to liberate the graphene particles from the host material”.
More and more materials are being enhanced with graphene, such as batteries, for its incredible properties.
Returning to surgical masks, a test carried out by the Canadian laboratory NanoSafe on ZenGuard brand equipment demonstrated that graphene remained within the masks during inhalation. These results corroborate the claims made by the Graphene Council and the RCS.
These assertions are also in line with the Graphene Flagship study, whose teams modeled the effects of exposure to graphene-laden composites on the lungs. They found that continuous exposure to graphene over long periods did not induce a significant immune response. This implies that the graphene present in these composites would have no negative impact on health, even in the event of long-term exposure.
According to their research (Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment, 2018), inhalation and epidermal absorption appear to be the most likely means of unintentional exposure, particularly in the working environment when handling graphene-based products. In the form of volatile powders (nanopowders), graphene presents a higher inhalation risk.
Studies have also been carried out on the effect of graphene alone, i.e. not incorporated into a matrix. An independent laboratory at the University of Strasbourg (Degradation of Single-Layer and Few-Layer Graphene by Neutrophil Myeloperoxidase, 2018) demonstrated via in vitro tests that, in the event of free graphene particles being inhaled or absorbed, certain human cells (lymphocytes, present in the immune system) naturally destroyed the graphene.
The graphene used in this study is a non-oxidized graphene with a low number of layers (FLG).
Graphene products and the end of the life cycle:
is there a health risk?
In addition to the risks associated with handling or using a graphene-containing product, we also need to consider the risks associated with its end-of-life. The main studies on the subject have modeled the end-of-life cycle of a graphene-doped material following abrasion.
According to the multidisciplinary Graphene Flagship team and its partners (Hazard assessment of abraded thermoplastic composites reinforced with reduced graphene oxide, 2022) including the Swiss laboratory EMPA, “graphene-based particles released from polymer composites after abrasion induce negligible health effects. The present findings show a negligible impact of rGO-reinforced PA6 composites on all the models tested, suggesting a likely low risk to human health at acute exposure conditions.”
Carbon Waters is also conducting an analysis of abrasion and fire degradation residues of an epoxy polymer enriched with Graph’Up, its range of performance additives, as part of the European Macramé project. Conducted with the EMPA laboratory and other project partners, this study will assess the cytotoxicity and ecotoxicity of Carbon Waters’ graphene-based performance additives. Results will be announced in the coming months.
What can we learn from studies on the safety of graphene?
While graphene has demonstrated its incredible properties over the years, it is essential to look at the health risks it may pose.
The various studies carried out on the subject all agree that the type of graphene, its quality, the degree of concentration and the level of exposure have different impacts. However, they show that graphene presents only a low risk under normal conditions of handling and exposure. This risk is lower if graphene is integrated within another material or object, unlike graphene in powder form, which, due to its high volatility, increases the likelihood of inhalation.
At a time when many substances are under regulatory scrutiny as being toxic, graphene-based additives are excellent candidates for sustainable substitution.
Carbon Waters, a company specializing in the production of FLG (Few-Layer Graphene) performance additives, offers pre-dispersed solutions, with no risk of inhalation during handling.
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