02.What are the risks?
Small particles, big risk
The very properties that make nanomaterials so attractive – their small size (that of atoms and molecules) and relatively larger surface area – can also make them potentially toxic to humans.
- They have far greater access to our body (bioavailability) than larger particles, resulting in greater uptake into individual cells, tissues and organs. This greater access and reactivity may introduce new toxicity risks. Numerous test tube studies (in vitro) have shown that nanomaterials can cause damage to cells and tissues in a number of ways, including changing the DNA and causing mitochondrial damage.
- There’s some evidence to suggest nanoparticles may be associated with rising levels of immune system dysfunction and inflammations of the gastrointestinal tract (GIT), including the suggestion that exposure may be associated with Crohn’s disease, a damaging and chronic inflammation of the GIT which can lead to cancer.
- There has been some research which shows that nanoparticles can cross the blood/brain barrier. A leading European toxicologist has said we cannot rule out a link between nanoparticles and diseases such as Alzheimer’s, Huntington’s and Parkinson’s.
There’s nothing inherently unsafe about very small particles — we are exposed to them every day. The air we breathe, the food we eat and water we drink all naturally contain particles within the nanometre range. Most health concerns relate to the potential impacts of deliberately manufactured nanoparticles that are different from anything that occurs in nature (see Nanotubes — The New Asbestos?, below).
The study of the toxicity of nanomaterials, “nanotoxicology”, is in its infancy, so rigorous safety information is limited. However, experts agree there is an urgent need for research in this area:
- We don’t know how nanoparticles in food are absorbed, transported around the body, accumulated or eliminated. Some nanoparticles may be able to transfer food components to parts of the body not normally exposed to them.
- Worse, we don’t know how to routinely test for the presence of nanomaterials in food, which is concerning since in order to assess the risk posed by any chemical we must first be able to identify and measure it.
Nanomaterials now in commercial use by the food industry, such as nanoscale titanium dioxide (used as an ultraviolet protector and an antimicrobial in food packaging and containers) and silver (used as an antimicrobial in food packaging, chopping boards and knives), have been shown to be toxic to cells and tissues in both test tube and animal studies.
Another area of concern is the potential for nanonutritional additives (functional foods) to provide an excessive dose of some vitamins and nutrients, or to interfere with the absorption of other nutrients. Dr Qasim Chaudhry, leader of the nanotechnology research team at the UK’s Central Science Laboratory, warns that nanoparticles and nanoencapsulated food ingredients “may have unanticipated effects, far greater absorption than intended or altered uptake of other nutrients, but little, if anything, is known currently”.
A recent study in mice found that some forms of carbon nanotubes may be as harmful as asbestos if inhaled in sufficient quantities.
There are many unanswered questions. It is still not clear whether carbon nanotubes will become airborne and be inhaled, or whether they still can successfully work their way to the sensitive outer lining of the lungs.
A pivotal report on nanotechnology by the Royal Society in the UK in 2004 recommended that, until there was evidence to the contrary, factories and research laboratories should treat manufactured nanoparticles and nanotubes as if they were hazardous.
Based on the results of this study, the toxicity and potential implications of long, multi-walled carbon nanotubes is an issue of priority for the Office of the Australian Safety and Compensation Council (ASCC). The ASCC has also initiated a nanotechnology occupational health and safety research program, while the NSW Department of State and Regional Development’s recent inquiry into nanotechnology recommended that a national mandatory labelling scheme be put in place for all engineered nanomaterials used in the workplace.