Sunscreens: the evidence
There has been some debate about the role of sunscreens in skin cancer prevention and the potential association of sunscreen use with melanoma risk. Follow-up on a randomised trial published in 2010 concluded that melanoma may be preventable in adults by regular use of sunscreen. A review found mounting evidence that sunscreen can prevent SCC, but no evidence that it can prevent BCC. A summary of the evidence published in 2007 also found no conclusive evidence that broad spectrum sunscreens prevented BCC. Test test test
It has also been suggested that people may use sunscreen in order to stay longer in the sun (by reducing the risk of burning), thus increasing their risk of cutaneous melanoma. However, Gallagher et al. caution that retrospective case–control studies of melanoma and sunscreen use should be interpreted with great care, because of subject recall problems and the inevitable confounding of sunscreen use with reduced exposure.
Daily sunscreen use has been shown to be both effective and cost-efficient in preventing squamous cell carcinomas and solar keratoses. While there is a lack of evidence that modern sunscreens prevent melanoma, their use, along with other sun protection strategies, is encouraged as a means of combating the year-on-year rise in melanoma incidence.
Nanotechnology has been used in sunscreens for many years. All sunscreens in Australia are tightly regulated through the Therapeutic Goods Administration (TGA). In early 2009, the TGA reviewed the scientific literature in relation to the use of nanoparticulate zinc oxide and titanium dioxide in sunscreens, concluding that:
- The potential for titanium dioxide and zinc oxide nanoparticles in sunscreens to cause adverse effects depends primarily upon the ability of the nanoparticles to reach viable skin cells; and
- The current weight of evidence suggests that titanium dioxide and zinc oxide nanoparticles do not reach viable skin cells; rather, they remain on the surface of the skin and in the outer layer of the skin composed of non-viable cells.
Drawing on the best available evidence, our current assessment is that nanoparticulates used in sunscreens do not pose a risk. However, Cancer Council Australia continues to monitor research and welcomes any new data that sheds more light on the topic.
- Green AC, Williams GM, Logan V, Strutton GM. Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol 2011 Jan 20;29(3):257-63 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/21135266.
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- Autier P. Sunscreen abuse for intentional sun exposure. Br J Dermatol 2009 Nov;161 Suppl 3:40-5 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/19775356.
- Gordon LG, Scuffham PA, van der Pols JC, McBride P, Williams GM, Green AC. Regular sunscreen use is a cost-effective approach to skin cancer prevention in subtropical settings. J Invest Dermatol 2009 Dec;129(12):2766-71 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/19536149.
- van der Pols JC, Williams GM, Pandeya N, Logan V, Green AC. Prolonged prevention of squamous cell carcinoma of the skin by regular sunscreen use. Cancer Epidemiol Biomarkers Prev 2006 Dec;15(12):2546-8 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/17132769.