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The Big Picture on Nanoparticle Safety

Credit: olly/Adobe

Credit: olly/Adobe

By Laurence Macia & Wojciech Chrzanowski

Nanoparticles are found in our food, cosmetics and tattoo inks, but regulations for their use aren’t keeping up with new research questioning their safety.

When Laura first wakes up, she makes a cup of white coffee with her capsule coffee machine. She then has a shower, uses some deodorant, applies a facial moisturising cream and foundation powder, brushes her teeth and puts on some lipstick, which she will reapply many times during the day. She is not so hungry as she had too much ice cream yesterday, so she will buy an iced doughnut on her way to the university. Outside, the sun is already up in the blue sky so she grabs some sunscreen to protect her skin. After a short walk she arrives for her chemistry class on food additives.

Laura is a bit distracted as she has friends coming over tonight and plans to make an amazing cake she saw on TV. To make this cake she will need to add 5 grams of titanium dioxide powder (food additive E171) that she purchased on the internet. She is not sure what it is, but it should be safe as she saw it on TV and the cake looks so white and great that she has to have it.

For her lunch break Laura buys a chicken and mayonnaise sandwich that she will eat on her way before she meets her boyfriend William, who is about to get his first tattoo. This tattoo will cover a significant part of his upper arm. He is a bit stressed and doesn’t have much appetite today. He just had a snack and now chews nervously on some gum before Laura joins him in the tattoo studio.

While the behaviours of Laura and William are common and can apply to any of us, many of the food products, cosmetics and all tattoo inks contain billions of nanoparticles that we consume or are exposed to every day. In fact, the amount of nanoparticles we ingest, as well as the number of products that utilise nanoparticles, is continuously increasing.
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Nanoparticle Uses

By definition, nanoparticles are natural or synthetic particles with sizes measured in nanometres (1 nm is 10 million times smaller than 1 cm, and 100,000 times smaller than the thickness of your hair). They can be found naturally (e.g. the casein protein in milk is encased in a lipid shell) or created artificially (e.g. silver nanoparticles used as antimicrobial agents).

The food industry has been using nanoparticle additives for more than a decade to make food look nicer (e.g. food colouring and whitening agents) or to improve food texture (e.g. emulsifiers found in ice cream or mayonnaise).

Aesthetic reasons also drove the cosmetics industry to introduce nanoparticles to make-up products as well as toothpastes and hair products. The anti­reflective or adsorbing properties of some nanoparticles see them used in shower gels, shampoos and sunscreens.

Finally, pharmaceutical companies also use nanoparticles to deliver drugs more effectively, eradicate bacterial infections or coat tablets to prevent the degradation of active ingredients.

Exposure to some nanoparticles can occur through entirely independent uses. For example, titanium dioxide is not only consumed in food at an average of 2 mg/kg of body weight per day, but is also used in the white ink used in tattoos, the white pigment in the paint covering our walls, and also in the white line markings on Wimbledon’s tennis courts.

Health Concerns

Our bodies are in contact with all these nanoparticles, but do they enter our bodies and interact with our cells? Biology is extremely complex, and there is no single parameter controlling how our body will interact with nanoparticles. It is rather the interplay of many of their features – such as size, shape, surface charge, chemistry and mechanical properties – that will define the fate of nanoparticles within biological systems. These parameters control cellular internalisation, toxicity, circulation time and distribution throughout the body as well as their degradation rate.

Unfortunately, how nanoparticles affect biological systems remains far from understood. There is a significant gap in the knowledge that we need to fill if we want to protect our health and environment while reaping the benefits of nanotechnology.

Therefore, our research group is developing new strategies to understand how the physical and chemical properties of nanoparticles affect their function, and thus the potential impact on our health and environment. Since the size, shape, mechanical properties and surface chemistry of nanoparticles orchestrate their cellular internalisation, toxicity, circulation time and biodistribution, all these parameters will dictate their potential impact within the body.

It is therefore critical to precisely examine the physicochemical characteristics of nanoparticles to define their safety. Furthermore, deep knowledge of nanoparticle structure is pivotal to guide manufacturing methods that ensure their functionality. While current characterisation tools have a limited detection range and have been unable to map these properties at the nanoscale, a team led by A/Prof Chrzanowski develops has developed atomic force microscopy-based techniques that can map interactions between nanoparticles and proteins, cells and tissues. By developing 3D liver models for toxicity assessment the team has discovered that individual nanoparticles induce aggregation and degradation of both intracellular and extracellular proteins.

While there is a steep increase in the development of new nanoparticles and applications, our understanding about their impacts on the environment and our health is still very poor. We need more research to define nanoparticle safety.

At this stage we don’t really know if nanoparticles could make us sick, but several independent studies have demonstrated that high doses of nanoparticles can aggravate disease. For example, mice that ingest titanium dioxide have worse inflammation of the colon (, which suggests that nanoparticles could aggravate disease in people susceptible to diseases like ulcerative colitis. There is also evidence that nanoparticles in some tattoo inks are highly toxic (

Alarming reports in the literature have demonstrated that nanoparticles accumulate in major organs such as the liver and colon, and impact on their function, induce lung injury and contribute to cancer development, alter cardiac function and vascular homeostasis. Furthermore, continuous exposure to nanoparticles in smog is linked to the development of chronic obstructive pulmonary disease.

Dr Macia’s research is focusing on understanding how nanoparticles in our food interact with the gut microbiome and the immune system to promote or aggravate the development of metabolic, autoimmune and allergic diseases. If immune cells are distracted by nanoparticles instead of focusing on pathogens, our ability to fight viral or bacterial infections could be reduced. More research is critically needed to unequivocally show their impact on health before our food and cosmetics become loaded with nanoparticle ingredients.
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Environmental Concerns

The extensive use of nanoparticles could also have environmental consequences. Nanoparticles used excessively in consumer products inevitably end up in the environment and contaminate our water and soil. There are already signals that soil contaminated with nanoparticles have a different microbiological profile that could impact negatively on crop quality.

Furthermore, the quantity of sunscreen contaminating the water at crowded Australian beaches is considerable. Fish will therefore ingest nanoparticles from dissolved sunscreen, and our consumption of these fish or their predators will increase our intake of nanoparticles.

Finally, the water we drink from our tap or plastic bottles is also polluted with nanoparticles that are too small to be filtered, thus adding to the contamination of water by plastic nanofibres.

Regulation of Nanoparticle Use

Many of the regulations governing nano­particles were developed several years ago and haven’t kept pace with new technologies and other developments, such as the ability to screen toxicity at levels that were unachievable a few years ago.

However, the growing evidence of possible risks posed by nanoparticles has seen the World Health Organization and the European Union conduct scientific and public consultations aimed at updating the guidelines for assessing the risk of nanomaterials. In fact, the EU is backing the development of a framework that would allow decisions on nanomaterial safety to be made in a growing range of products, including clothing, medicines, cosmetics and electronics, to overhaul the present system of individually assessing the risks posed by thousands of nanomaterials in these applications. Unfortunately, Australian regulations remain stagnant and mostly regard nanomaterials as conventional chemicals tested in a similar way to macro- and microscale materials.

One could argue that the WHO and EU examples, as well as significant advances in our knowledge and technological capabilities, should prompt a mature discussion on the safety of nanomaterials. After a decade of daily consumption, one could argue that we have reached a critical moment when we will start detecting the long-term effects of nanoparticles on our heath. Already at the population scale we have seen increased incidences of autoimmune diseases, fertility issues, asthma, chronic obstructive pulmonary disease and food allergies. These remain unexplained and could be linked to increasing exposure to nanoparticles.

After reading this article, Laura and William decided to avoid nanoparticles as much as they can. How can they do that? First, they can start by reducing the consumption of processed food, such as hard-coated lollies, hard-coated chewing gums, creamers and cakes with high icing sugar content (check the label to see if nanoparticles are present). They can also carefully read food labels and avoid any food containing products with E171 or silicon dioxide.

A complete avoidance of nanoparticles is not feasible because some provide benefits to us. For example, sunscreens contain nanoparticles but we must use them for protection against UV rays.

The good news is that our knowledge in this area is growing, and we understand more how nanoparticles interact with proteins, cell and tissues. In the near future we will be able to make evidence-based recommendations regarding their safety and make safe-by-design nanoparticles that will bring significant social and health benefits.

Wojciech Chrzanowski leads the Nanomedicine Laboratory and Nano-Bio-Characterisation facility in the University of Sydney’s Faculty of Pharmacy. Laurence Macia is a biomedical scientist in the University of Sydney’s School of Pharmacy and Nano Institute.