Sunscreen and nanoparticles

Could your sunscreen be doing you more harm than good?
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01 .Sunscreens and nanoparticles


While the jury is still out on the risks associated with nano ingredients in sunscreens and cosmetics, there is concern that “slopping” could be doing more harm than good. 

In the absence of compulsory labelling that forces manufacturers to reveal the presence of nanoparticles, consumers either have had to rely on the assurances of manufacturers that their sunscreens are nano-free - though as it turns out, this is no guarantee - or take their chances with one of the handful of sunscreens that claim to be natural. 

CHOICE believes nanoparticles should be labelled on all products so consumers can choose to avoid them if they wish. In 2010, we tested 12 sunscreens and found while several contained nanoparticles, only one contained a significant amount and four were nano-free.

How do sunscreens work?

Sunscreen contains one or both of the following types of active ingredients:
  • Chemical absorbers absorb UV radiation and stop it reaching your skin. They can irritate and even cause allergies, but of deeper concern is their role as endocrine disruptors and skin penetration enhancers (which have implications for people in contact with other chemicals, such as agricultural pesticides).
  • Physical blockers, which are zinc oxide and titanium dioxide, reflect and scatter UV radiation. They have generally been considered safer and more effective than chemical absorbers, are better for sensitive skin and renowned for their broad- spectrum UV radiation-blocking abilities. It was discovered that micronising physical blockers resolved the unwanted ghostly look these sunscreens gave, but there are now concerns that these small particles fall into the nano range.

What are nanoparticles?

Nanoparticles are particles with one or more dimension less than 100nm (where one nanometer is one-billionth of a metre). They exhibit different properties compared with larger particles of the same material, due mostly to the high surface to volume ratio, which can make the particles very reactive. There are various health and environmental concerns around nanoparticles because they’re able to penetrate cells in organisms, and their interactions with biological systems are relatively unknown.

Why the concern about nanoparticles in sunscreen?

Several years ago, Colorbond painted roofing showed accelerated deterioration in fingerprint-shaped patches. Sunscreen used by builders was suspected, and research published by Colorbond manufacturer BlueScope Steel in 2008 confirmed that certain nanoparticles in titanium dioxide-based sunscreens were the culprit.

Other lab tests have indicated that nanoparticles of zinc oxide and titanium dioxide may create free radicals that cause damage to cellular DNA and mitochondria, particularly in the presence of UV light. Free radical damage may also lead to cancer. So if it’s destroying painted surfaces and DNA, should we be putting it on our skin?


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In order for nanoparticles in sunscreens to be considered dangerous, they have to firstly penetrate the skin, then go somewhere they can do significant damage. For now, there is no solid proof this can happen. 

How it works

To get through the skin, the particles have to be small enough. Zinc oxide and titanium dioxide are often manufactured in nano-size particles, but they tend to clump together. These “clumps” are known as “aggregates”, which can in turn clump together to form "agglomerates". While agglomerates break up fairly easily, aggregates require enormous amounts of energy to break up, and wouldn’t do so in the normal use of sunscreens. Sunscreen maker Hamilton Laboratories commissioned testing of their own sunscreens, which contained primary particles in the nano range, but in the finished products found no nanoparticles, suggesting the primary particles had formed larger aggregates. When we tested sunscreens in 2010, we found few nano-size particles present in sunscreens, suggesting either the primary particles were mostly aggregating or that the primary particle size used was larger than the nano-range. 

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