SUN CARE
The importance of the fact that the particles do not penetrate through the skin becomes apparent when one considers an oft-quoted formula for risk assessment:
Risk = Hazard x Exposure
Since the particles cannot reach living skin cells or enter the body, the ‘exposure’ term is effectively zero; therefore, as concluded by Schilling et al: “the risk for humans from the usage of nano-structured TiO2
or ZnO
currently used in cosmetic preparations or sunscreens is considered negligible”.
Regulatory aspects Europe
The new Cosmetics Regulation, which comes into force in July 2013, requires that a notification be submitted to the European Commission for any new cosmetic product, before the product is placed on the market. This notification includes information such as the identity and category of the product, name and address of a nominated responsible person, the country of origin and the member state where the product is to be placed on the market, and the frame formulation. This standard notification requirement applies to all cosmetic products. In the case of products that contain nanomaterials, these must also be specified in the notification, along with “reasonably foreseeable exposure conditions”.
Article 16 of the Regulation further requires that products containing nanomaterials must be notified to the Commission at least six months prior to being placed on the market, along with a data set including characterisation (eg. particle size data) and toxicological data. However, these additional notification requirements do not apply to nanomaterials used as colorants, UV filters or preservatives, as these are already subject to positive listing in the annexes. However, all products containing nanomaterials will be required to state this in the ingredient listing by including ‘nano’ in brackets after the relevant material – for example ‘titanium dioxide (nano)’. Although most consumers pay little if any attention to INCI listings on products, it is perhaps this labelling requirement more than anything which has caused some manufacturers to seek to avoid using nanomaterials – they fear that consumers will avoid products containing ‘nano’ ingredients due to negative stories in the popular press. In the opinion of this author, it is important that we as an industry promote the proven safety and benefits of nano-sized inorganic sunscreens, so that the nano label can be seen as positive
rather than negative. Of course this will not be easy – for the popular press, a story about ‘the hidden dangers in your skin cream’ is more interesting and newsworthy than a positive story about the safety of cosmetics – in fact the latter is not news at all, as it is normal and essential for any cosmetic product to be safe. A key aspect of complying with the Cosmetic Regulation requirements, of course, is being able to identify whether your product does include a nanomaterial. The current nanomaterial definition in the Regulation, quoted earlier in this article, needs more detail for it to be practically useful. At present the definition makes no mention of how the particle size should be measured, or what proportion of particles should be in the specified size range in order to define something as a nanomaterial. Work is still ongoing to finalise these details.
Another matter still to be resolved in Europe is the status of zinc oxide as a sunscreen. In 2008, as a result of the growing debate around nanotechnology, the former SCCP (now the SCCS) decided to re-review the safety of nano TiO2
and ZnO,
and asked stakeholders to submit data on various issues. Detailed dossiers have now been compiled, and a summary of these and their conclusions is available.8
TiO2 is,
of course, on the list of permitted UV filters in Europe; however ZnO had still not been added to this list when concerns over nanomaterials first arose, and the nano debate has now further delayed this. It is to be hoped that, once the SCCS has had the opportunity to review the full data set, nano ZnO will also be permitted as a sunscreen in Europe (as it is everywhere else in the world).
Rest of the world In the US, TiO2
and ZnO are approved UV
filters, regardless of whether they are nano- scale or not. The FDA Sunscreen Monograph, which is yet to be finalised, does not include any special regulations or labelling requirements for nanomaterials. In June 2011, the FDA published new rules for testing and labelling of sunscreens; these rules again make no specific mention of nanoscale ingredients. However, in a press conference to announce the new rules, the FDA did state that it had reviewed the available literature and done its own tests on skin penetration. It had concluded that nanoscale inorganic sunscreens do not penetrate the skin and are safe for human use. At present the agency does not plan any additional regulations or restrictions on the use of these materials.
In Australia, the Therapeutic Goods Administration conducted a review of
scientific literature on nanoscale TiO2 and
ZnO in sunscreens in 2009. It concluded that the particles do not reach viable skin cells; rather, they remain on the surface of the skin and in the outer layer of the skin that is composed of non-viable cells. Therefore, the TGA regards these materials as safe for use in sunscreens and does not require any additional labelling for them. At present, no other major markets have any specific labelling requirements or regulatory restrictions for nanoscale inorganic sunscreen ingredients.
Conclusion
Nano-sized inorganic sunscreens have been with us for more than 20 years now, with no reported evidence of adverse health effects from their extensive use in sunscreen products around the world. Unlike some other more novel types of nanomaterials, fine particle TiO2
and ZnO
have been subjected to extensive safety testing, particularly with regard to the question of whether these materials can penetrate through the skin. The overwhelming conclusion from these studies is that there is no penetration beyond the outer layers of the stratum corneum, and that these ingredients are safe for use on human skin. Most regulatory bodies around the world have recognised this and at present have no plans to impose specific restrictions or labelling requirements for nanoscale inorganic sunscreens. The exception is in Europe, where the new Cosmetic Regulation will require nanomaterials to be identified in ingredient listings. However, the detail of the regulatory definition of nanomaterials is yet to be finalised, so it is not yet clear which grades will be classed as nanomaterials and which will not.
References 1 British Standards Institute Publically Available Specification. Terminology for Nanomaterials. PAS 136: 2007.
2 Mie G. Phys. Lpz.1908; 25:377. 3 Robb JL, Simpson LA, Tunstall DF. DCI magazine, March 1994.
4 Tooley IR, Hewitt JP. Characterisation of titanium dioxide nanoparticles in sunscreens. Poster presented at the 12th Florida Sunscreen Symposium, Orlando, September 2009.
5 Renner G. The EU Cosmetics Regulation 1223/2009, Scancos Conference, Stockholm, November 2011.
6
ec.europa.eu./comm/health/ph_risk/committees/ sccp/documents/out135_en.pdf
7 Nohynek GJ et al. Grey goo on the skin? Nanotechnology, cosmetic and sunscreen safety. Critical Reviews in Toxicology 2007; 37: 251-77.
8 Schilling K et al. Human safety review of ‘nano’ titanium dioxide and zinc oxide. Photochem Photobiol Sci 2010; 9: 495-509.
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