The great nanoparticle debate

The great nanoparticle debate

Here at Sol, we choose to use natural mineral zinc oxide as the active ingredient in our sunscreen over chemical ingredients due to the concerns regarding our coral ecosystem and human health.

Some of you will be aware of the controversial discussion around nano versus non-nano zinc and its relationship to human health and our environment.

There is a lot of information on nano materials out there, and through the formulation of our product we’ve carefully weighed all our options up.

In fact, we’ve spent hours poring over numerous research papers and technical information, so you can spend more time enjoying the beach, the water, the bush, or anywhere else in the great outdoors knowing you’re safely protecting yourself from the sun, while also protecting our planet!

Cheers to that. So, here’s the deal.


What is nanomaterial?

While nanomaterial is typically defined as particles between 1 and 100 nano metre in size, there is currently no consensus worldwide about thresholds for percentages of particles in this size and other qualifications on what constitutes nano material. Government agencies around the world are working to define, and update definitions.

For example, many zinc oxide sunscreens, and even some chemical sunscreens claim that their sunscreens are non nano. And while the median particle size may be, say, 135 nano metres, there would still be a significant percentage of particles below 100 nano metres.

The zinc we use in our sunscreen is primarily made of nanoparticles, that form larger coated non nano clusters through our formulation process. This process allows our zinc to blend so well into the skin and avoid looking like you’ve seen a ghost, while offering both high UVB and UVA SPF protection. Current New Zealand regulations require us to label our zinc nano due to our zinc primarily starting out in nano form.

As you can see, the lines are blurred.

In a nutshell, the jury globally appears to be out with regards to the correct parameters of definition for nano, going as far to suggest the use of the term non nano in some instances may simply be used for marketing purposes, by implying nano is worse than its non-nano counterpart when that may not necessarily be the case.


So, is our zinc safe to put on your skin?

Many regulators and bodies worldwide including the European Union Scientific Committee on Consumer Safety and the environmental non-profit USA Environmental Working Group, have come to the same conclusion that zinc in nano form is safe, because research suggests in does not penetrate the skin and there is no evidence that zinc oxide nano particles can cross the skin in significant amounts.

Zinc oxide sits on the outer, dead, layer of skin, and any free radicals generated will not affect living cells below. Furthermore, our zinc oxide is very photo stable so generates much lower levels of free radicals than some other zinc formulas, and any free radicals that may form through exposure to sunlight would theoretically be quenched by the skin’s own antioxidant protections.


What about our coral reefs?

The bleaching of coral reefs is real, but most evidence suggests this is primarily from higher water temperatures and industrial /agricultural pollution.

If you were listening during those science lessons during high school, you’ll know that zinc is a naturally occurring element found in all surface waters. Like many nutrients, it can be essential and beneficial at low levels, but it can be aquatic hazardous in bulk concentrations.

To remain beneficial, levels must be maintained at ‘no observed effect’ for toxicity, based on realistic concentrations for the real world environment, so that when equated to the volume of water and turnover of zinc in terms of animal or plant respiration, the levels do not increase anywhere into toxic zones, and remain within a safe range for coral reefs.

Interestingly, a study on the comparative dissolution, uptake, and toxicity of zinc oxide particles in individual aquatic species and mixed populations by the United States National Library of Medicine found that although lab results may give us some helpful insights, they may not necessarily reflect real life applications as these tests are often completed at extreme high concentrations and usually on individual species. The same study also indicated that it’s the concentration of zinc which can
cause harm to aquatic species, rather than the particle size.

The topic is complex to say the least, and there is very little concrete real-world evidence to date that zinc can damage coral reefs, since low concentrations are found in the sea and science points to zinc not building up on reefs over decades of constant use.

Obviously, common sense tells us that anything we add to our oceans and environment is going to have some kind of impact, so anything we can do to lessen the impact is a win, including making good sunscreen choices.

The ambiguity surrounding this topic is huge, but we know that the following guidelines can all help keep our coral reefs and natural environments safe for future generations to enjoy:

  1.  Wear sun protection clothing to reduce the amount of sunscreen you need to wear
  2. Avoid the two more harmful chemicals for reefs found in sunscreen (oxybenzone and octinoxate)
  3. Choose a mineral-based formula like zinc oxide
  4. Use a rub on (versus spray), water resistant formula that’s more difficult to wash off and less likely to come off in the water.
  5. We think our Sol sunscreen is a good choice!

We’re keeping a watchful eye on this subject, and are constantly seeking to balance science, our desire to care for our environment, and practical real world application to provide better suncare for you, and our planet.



  • While nano is defined as particles smaller between 1 and 100 nano metre in size, that doesn’t always mean the product you purchase will contain no nano particles because there are no clear international guidelines.
  • Not all nano zinc oxide is created equally. The zinc we use in our sunscreen starts out in nano form but becomes coated, non nano particles through formulation.
  • There is no evidence to suggest zinc oxide nano particles can cross the skin barrier and cause harm to human health.
  • It’s the concentration of zinc, rather than the particle size, that could have a detrimental impact on aquatic life.
  • Water resistant, rub on sunscreen with zinc oxide is one of the safest choices for our coral reefs, and the quantities used in sunscreen are unlikely to have an impact in amounts found in our oceans.
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