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Sunscreens Revisited

by Dr. Randy

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Sunny weather is here again and with it comes concerns about sun exposure and sunburn. The sun is beneficial for its ability to induce vitamin D production in our bodies. For those people who take cod liver oil in the winter for its vitamin D value, it may be prudent to switch during the sunny summer months to fish oil or krill oil as an omega 3 supplement, which do not contain vitamin D. It may be possible to build up too high a level of vitamin D in the bloodstream. Be aware, however, that research has failed to show any toxicity from vitamin D3 supplementation in adults at dosages as high as 4,000 to 10,000 IU. The synthetic Vitamin D2 (ergocalciferol) has shown toxic potential. We cannot get too much vitamin D from sun exposure.

Sunscreens are necessary for days with hours of time spent in the sun, especially kids playing baseball, or playing at the park, or swimming. As for sunscreens, I am very concerned about the use of ingredients in most commercial brands. Many of these chemical sunscreens have carcinogenic and/or hormone disrupting effects. These include cinnamates, PABA, oxybenzone, salicylates, benzophenones, and triethenolamine, among others. These ingredients are absorbed through the skin, and can be found in plasma and urine samples after their use in humans. I don’t consider them safe for anyone, especially children.

Titanium dioxide (TiO2) is contained in many “natural” sunscreens, but this metal has also been implicated as a potential problem in humans. Titanium dioxide has the ability to cause DNA damage in human cells. Although the Environmental Protection Agency has not identified any carcinogenic effects of TiO2, its ability to alter DNA strands is a cause for concern.

Zinc oxide is the only completely safe sunblocking agent. In addition zinc oxide also has anti-inflammatory effects that can help to mitigate damage caused by UV radiation. Zinc oxide blocks both UVA and UVB radiation. Excellent sunscreen products that contain only zinc oxide as the active ingredient are made by UVNaturalUSA.com. Their Sport 30 is the most water repellent of their products. These sunscreens use a transparent zinc oxide that does not create a white mask on the skin. They can be ordered through many online sources and health food stores, and patients in my area can purchase it at my office. These sunscreens are safe for most infants as well. A thin layer works well. If swimming, reapply every 2 hours.

Enjoy the sunny weather. Avoid getting sunburned and be prudent about sun exposure at midday. Wear a hat. Protect your eyes with UV sunglasses. Use a zinc oxide sunscreen. And have fun.

Titanium Dioxide Studies

Chemical oxidation and DNA damage catalyzed by
inorganic sunscreen ingredients.

Dunford R, Salinaro A, Cai L, Serpone N,
Horikoshi S, Hidaka H, Knowland J

University of Oxford, Department of
Biochemistry, UK.

This is now a known carcinogen titanium dioxide (TiO2) has been noted (US
Federal Register, 43FR38206, 25 August 1978) to
be an unsafe physical sunscreen because it
reflects and scatters UVB and UVA in sunlight.
However, TiO2 absorbs about 70% of incident UV,
and in aqueous environments this leads to
the generation of hydroxyl radicals which can
initiate oxidations. Using chemical methods, we
show that all sunscreen TiO2 samples tested
catalyze the photo-oxidation of a representative
organic substrate (phenol). We also show that
sunlight-illuminated TiO2 catalyses DNA damage
both in vitro and in human cells. These results
may be relevant to the overall effects of sunscreens.

PMID: 9414101, UI: 98074912

45: Toxicol Lett 1995 Oct;80(1-3):61-7

*****

Deleterious effects of sunscreen titanium dioxide nanoparticles on DNA: efforts to limit DNA damage by particle surface modification

Serpone, Nick; Salinaro, Angela; Emeline, A.

Proc. SPIE Vol. 4258, p. 86-98, Nanoparticles and Nanostructured Surfaces: Novel Reporters with Biological Applications, Catherine J. Murphy; Ed.

(c) 2001 SPIE–The International Society for Optical Engineering.

Abstract

Sunlight can have deleterious effects on humans: causes sunburns and is the principal cause of skin cancers. Usage of TiO2 (and ZnO) in sunscreen lotions, widely used as UVA/UVB blockers, and intended to prevent sunburns and to protect consumers from skin cancers (carcinomas and melanomas) is examined. Although used to mineralize many undesired organic pollutants, TiO2 is considered to be a safe physical sunscreen agent because it reflects and scatters both UVB (290-320 nm) and UVA (320-400 nm) sunlight; however, it also absorbs substantial UV radiation which, in aqueous media, yields hydroxyl radial ((DOT)OH) species. These species cause substantial damage to DNA (J. Photochem.Photobio.A:Chem.,111(1997)205). Most importantly, sunlight-illuminated sunscreen TiO2 particles catalyze DNA damage both in vitro and in human cells (FEBS Letters, 418 (1997)87). These results raise concerns on the overall effects of sunscreens and raise the question on the suitability of photoactive TiO2 as a sunscreen component without further studies. The photocatalytically active nature of these metal oxides necessitates some changes since even the TiO2 specimens currently used in suncreams cause significant DNA strand breaks.

Chemical oxidation and DNA damage catalysed by inorganic sunscreen ingredients

FEBS Letters, Vol 418, 24 November 1997, pages 87-90

Copyright © 1997 Federation of European Biochemical Societies. Published by Elsevier Science B.V.

Rosemary Dunford, Angela Salinaro, et al.

University of Oxford, Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK
Department of Chemistry and Biochemistry, Concordia University, Montreal, Que. H3G 1M8, Canada
Department of Chemistry, Meisei University, Hino-shi, Tokyo 191, Japan

Abstract

Titanium dioxide (TiO2) has been noted (US Federal Register, 43FR38206, 25 August 1978) to be a safe physical sunscreen because it reflects and scatters UVB and UVA in sunlight. However, TiO2 absorbs about 70% of incident UV, and in aqueous environments this leads to the generation of hydroxyl radicals which can initiate oxidations. Using chemical methods, we show that all sunscreen TiO2 samples tested catalyse the photo-oxidation of a representative organic substrate (phenol). We also show that sunlight-illuminated TiO2 catalyses DNA damage both in vitro and in human cells. These results may be relevant to the overall effects of sunscreens.

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