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There have been various stories in the news in the past couple of weeks in Australia about peoples perception of nanoparticles in sunscreen.

To quote from the linked story above:

This week, the Federal Department of Innovation released the results of an online survey which found that one in four people who have heard about nanoparticle sunscreen have decided to avoid using sunscreen altogether.

This statement from the same story is not exactly reassuring:

There is a theory in the laboratory that they could cause harm but these nanoparticles have been in some sunscreens for years and there is no documented harm

So does there exist enough study or research to confirm or deny the health risks associated with the inclusion of nanoparticles in sunscreen?

If research is limited should people be worried enough that they should stop using these types of sunscreens or is this unwarranted?

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Answer copied in part from: Does sun screen cause cancer?

A critical review of the existing evidence for sun-screens has been published.

  • Burnett, M. E. and Wang, S. Q. (2011), Current sunscreen controversies: a critical review. Photodermatology, Photoimmunology & Photomedicine, 27: 58–67. doi: 10.1111/j.1600-0781.2011.00557.x

They looked at:

  • Whether sunscreens stop skin-cancers.
  • Whether sunscreens hinder the production of Vitamin D.
  • Whether the controversial ingredients were shown to cause harm, specifically:
    • oxybenzone and hormonal homeostasis,
    • retinyl palmitate and cancer
    • nanoparticles of zinc oxide (ZnO) and titanium dioxide (TiO2) and toxicity through the skin.

For this question, only the last issue is relevant.

Nanoparticles

The nanoparticle debate extends past just sunscreens, into other personal care and cosmetic products. They are widely used and have had a good safety record.

Nonetheless, some studies in rats suggested they may be photogenotoxic.

Considerable data assessing the potential toxicity of these materials in sunscreens has been published to date, and the studies referenced above were performed in controlled environments on healthy, undamaged skin. It has been established that the stratum corneum is an effective barrier preventing the entry of nano-ZnO and -TiO2 into deeper layers of the skin. Nonetheless, it remains to be determined whether a greater degree of penetration occurs through skin that is damaged, diseased or otherwise compromised. At the present time, however, the available data do not provide conclusive evidence demonstrating that damaged skin leads to an increased penetration of nanoparticles.

In summary, if your skin is undamaged, the nanoparticles can't get through. If your skin is damaged, there is no good evidence they get through, but more research is required.

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