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Nanotechnology - Applications, Trends and Risks

09/2006, 06.04.2006

BfR gathers up-to-date information on nano particles in consumer-related application areas

The use of nano particles is by no means as new as some of the spectacular products on the market would have us believe. Nanotechnology already arrived on the scene in consumer products, even if it wasn’t explicitly labelled as such, decades ago in varnishes and medicinal products. Nano particles from titanium dioxide or zinc oxide have also been used in cosmetics for some time as UV filters. Despite the widespread use of this technology, there are still unanswered questions from the risk assessment angle. An expert meeting at the Federal Institute for Risk Assessment (BfR) on 28 March 2006 examined current questions on products containing nano particles and the risks for consumers.

Nanotechnological applications for product manufacture involve the addition of substances with a particle size of between 0.1 and 100 nanometres (10^-9 metres) Many people already see nanotechnology as the key technology of the 21^st century. However, the question is increasingly being raised whether the promised benefits of new products with nanotechnology might not also be linked to unknown risks. At the expert meeting of scientists from research, practice and industry at BfR, the debate focussed on the three application areas: cosmetics, foods and consumer products. They discussed issues relating to substance properties, production stages, trends in consumer-relevant areas and, above all, the risks of the finished products.

The use of nano particles in cosmetics is relatively transparent. Substances on this scale are used for specific purposes in hair care products, skin creams and sunscreens. Nano pigments made of titanium dioxide or zinc dioxide used as UV filters in sunscreens are the most widespread. The pigments protect the skin by functioning like tiny mineral mirrors which reflect or absorb the UV rays.

The behaviour of nano particles applied to the skin has been well investigated in the case of titanium dioxide and zinc oxide. All the findings presented at the expert meeting showed that the nano particles do not penetrate healthy skin cells. They are mainly distributed over the skin surface. They reach deeper layers via the hair follicles (root sheaths) where they remain for some time. Hair growth then transports the nano particles back to the surface. It was observed that nano pigments penetrate more deeply when the skin has micro injuries. On the risk issue the experts came to the conclusion that, at the present time, there are no indications of a specific "nano toxicology".

By contrast, the use of nanotechnology in the food industry is not transparent. The key question is: What improved properties can be achieved by using nano compounds in foods? Experts believe that the development of novel foods with new or modified molecular structures is a promising future application area. In the USA the Food and Drug Administration has already approved some products containing nano particles. As far as the experts in the USA are aware, there have been no reports of health risks up to now.

In some consumer products nano-sized particles are used because of their physical and chemical properties. In the case of packaging their ability to act as barriers to oxygen, carbon dioxide and water is important or they are utilised as sunscreens or to improve mechanical and thermal properties. For instance, specific nano compounds are used in the plastic polyamide. The probability that these particles migrate to the packaged food is deemed to be very low as these coatings are on the outside. Other packagings are vacuum-coated with nano layers of aluminium or silicon oxide. It is not yet clear whether particles are released from inorganic coatings of this kind.

Nanotechnology has already been used for several decades in varnishes. The small particles are bound there in a mechanically active form. Other application areas are antimicrobial coatings for kitchen appliances and textiles modified with nano particles.  In textiles nano particles can be used to develop dirt-repellent surfaces and as effective moisture barriers. Antimicrobial silver nano particles are used in shoe soles and in some clothing items.

For the investigation and detection of nano particles, the parallel use of several analytical methods is recommended at present. There are many open questions from the risk assessment angle. The next challenge is to establish the suitable test strategies for identifying health risks.

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