Opinion
Safety warnings for nano sunscreens aren't justified, researchers argue.
Credit: iStockphoto
SUNSCREENS ARE AN IMPORTANT public health issue for Australians, and deserve balanced reporting. This involves weighing up the known risk of skin damage from excessive ultraviolet (UV) light exposure with a perceived risk of using nano sunscreens.
Sun damage occurs from penetration into the skin by UVA and UVB radiation. Both UVA and UVB can damage the genetic material inside a cell – an effect called genotoxicity, which can lead to tumour formation.
But UVA penetrates much deeper into the skin than UVB and has the main genotoxic effect on the cells in the basal epidermal layer of skin, where most skin cancers originate. So sunscreens that are effective blockers across a broad UV spectrum provide the best skin protection.
Misinformation in the public arena may stop parents and teachers from using the broadest UV protective sunscreens on children – especially those metal oxide-containing sunscreens that provide very good protection against harmful UVA exposure.IN MAY 2011, the Victorian State branch of the Australian Education Union voted to urge schools to use nano-free sunscreens as part of their Sunsmart programs, until research conclusively proves that nano-products are not toxic.
Schoolchildren need to be using the most protective sunscreens available, as severe sunburn in children is a major risk factor for melanoma incidence in adults. The most effective broad spectrum UV blockers are the physical blockers, such as the metal oxides zinc oxide and titanium dioxide. These both absorb and reflect UV, don’t break down under UV exposure and are longer-acting than organic UV blockers.
Concerns about nano-sunscreens have been mounting since a report three years ago by BlueScope Steel researchers Philip Barker and Amos Branch stating metal oxide nanoparticles in some sunscreens had photocatalytic activity – an accelerated photoreaction - capable of bleaching painted surfaces of coated steel. This draws a long bow, as both the nature of the target site affected and the UV-sunscreen co-exposure circumstances are very different.
Several studies have since shown that there is negligible penetration of metal oxide nanoparticles past the outer dead cell layer (in the stratum corneum) of healthy or damaged skin. The skin is also constantly shedding its outer layer of dead cells.
THE OFTEN-MENTIONED in vitro studies, that show zinc oxide nanoparticles are slightly positive for causing DNA damage using two specific cell exposure systems, have been difficult to relate to the whole body situation, because of an identified experimental artefact known as “psuedo-photoclastogenicity” (“clastogenicity” is chromosomal damage, a form of genotoxicity).
This pseudo effect may occur because of an increased sensitivity of these cells after UV exposure. Importantly, all in vivo and most in vitro genotoxicity tests were negative for zinc oxide.
Concerns about nano-metal oxides easily penetrating human skin specifically have not been supported by the latest research. A landmark Australian study, led by Brian Gulson of Macquarie University in Sydney (Toxicological Sciences, 2010), directly measured the absorption of zinc from sunscreen formulations in humans with concurrent UV exposure under typical beach conditions, and showed minimal absorption of zinc from both nano and bulk zinc oxide.
Zinc ions found in the blood from sunscreen during the researcher’s five-day beach trial were only 1/1000th of the total blood zinc levels. As zinc is an essential metal for maintaining good health, this very small amount of zinc would easily be handled by the body.
RECENTLY, THERE HAVE been calls from NGOs and consumer groups for the mandatory labelling of products containing engineered nanoparticles, especially sunscreens. This is a complex issue, as the importance of providing consumers with appropriate labelling information to guide their purchasing decisions is being subverted by the current potential for misinformation and misuse of any type of nano-labelling.
This is a major problem in going forward on the nano-labelling issue. A marketing firm has already used the term ‘not nano’ as a positive indicator for one sunscreen product, which implies that ‘nano’ must be bad, even when we know that particle size is not the only factor that may influence a potential hazard, and also that there are many well-known cases of micro-sized particles and fibres being hazardous.
It’s important to realise that not all nanoparticles behave in the same way biologically, or are potentially hazardous. Many engineered nanoparticles have been designed with both function and safety in mind.
Advances in nano-medicine, nano-biotechnology and nano-safety research are rapidly building our capability to re-engineer nanoparticles to be even safer. The rushed implementation of a market-wide generic label in the present climate, such as a label stating “This product contains engineered nanoparticles” would be automatically misinterpreted by consumers as meaning that it contains a hazard.
Nano-sized metal oxides absorb UV light better as particle size gets smaller, and have the added advantage of a transparent appearance. As zinc oxide nanoparticles are also less reactive to UV light, less-penetrating and less-persistent than titanium dioxide, I'd recommend non-aerosol sunscreens containing zinc oxide in either the bulk or nano forms.
As Australia has the highest incidence of skin cancer, it is crucial that people do not stop using the most protective sunscreens because of misinformation, or misunderstanding the nano label issue.
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Paul Wright is an associate professor and the co-ordinator of Nanosafe Australia at RMIT University in Melbourne and is conducting government-funded research into the safety of nanoparticles used in sunscreens.
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Fonte: Cosmos
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REFLEXÃO:
Faço os mesmos comentários do texto anterior.
Também havia feito um comentário no próprio site do Cosmos que reproduzo para vocês; com um pequeno alerta, eles moderaram o comentário, fazendo algumas alterações. O meu comentário é o primeiro.
E tem uma frase que eles deturparam completamente: We Hitori at a time that we engage the people to decide on the risks we want. Here are the paradigm of human risk.Não sei o que é Hitori, o que queria dizer é que nós estamos num momento da História que devemos incluir as pessoas para decidir os riscos que queremos para o futuro, aí o paradigma do risco humano.
Foi isso que eu disse, mas como eles moderaram acabaram deturpando o que eu disse. Mas vida que segue.
Readers' comments
Nano
Regarding the labeling of nano sunscreens, can not businesses (for-profit) over the protection of consumers. If the term nano can not be used to warn of hazards in products, then companies can not Fabries anything containing nano until the polls actually show that it is not toxic.
Here in Brazil, unfortunately, also has high rates of skin cancer, but the dangers of nanoparticles in sunscreens can not be worse than those made by the sun. We Hitori at a time that we engage the people to decide on the risks we want. Here are the paradigm of human risk.
Here in Brazil, unfortunately, also has high rates of skin cancer, but the dangers of nanoparticles in sunscreens can not be worse than those made by the sun. We Hitori at a time that we engage the people to decide on the risks we want. Here are the paradigm of human risk.
Submitted by Visitor on 5 October 2011 - 6:41am.
I would be happy with a