Zinc and the Nano Sunscreen Revolution

Between 12^th and 16^th March 2009 I took part in a trial to investigate the fate of nanoparticles on the skin. Nano particles are the ingredients that have helped to make sunscreens containing Zinc and Titanium “invisible”. I remember growing up in the UK and being plastered in a thick, white pasty sun creams that more often than not smelt like coconut. Should that not be available, the factor 8 oil came out, leaving your skin looking like you’ve just bathed in a chip pan (does anyone still have a chip pan…..?) Anyway, the world has turned a few times since then and sunscreens have become a whole lot more sophisticated.

Nano Zinc and titanium became popular in the late 1990’s as the technology for making these small particles became more commercially viable. Many companies sell nano sized Zinc and as these ingredients open the door for light weight, high protection, broad spectrum sunscreens to be developed in an inorganic only filter base. Nano Zinc and Titanium have also found use in the anti-ageing and SPF 15 moisturizing cream as formulators became able to develop creams, lotions, sprays and foams that went onto the skin without leaving the wearer a ghostly shade of white. Also as Zinc and Titanium actives work on the surface of the skin, they are preferred in products for babies or for those with sensitive skins – an elegant product offering for this market segment was most welcomed. It seemed that it was sunny side up at every turn!

Unfortunately, with every happy innovation should come a degree of caution. When you take something like Zinc or Titanium and create nanoparticles you not only change the physical characteristics of the particle, you may also change its chemical reactivity. A nanoparticle is a particle who’s size is 100nm or smaller. With an average human hair being 80,000nm across you can see that these things really are tiny. Physically such small particles may be able to enter the body through inhalation of the material when manufacturing, through ingestion (consumer product not wiped off the hands or licked) or through dermal penetration as a consequence of normal product usage. Chemically nanoparticles may be much more reactive than their larger conterparts. They may do all kinds of things that their big brothers and sisters would never dream of doing such as bonding to other chemical ingredients, forming free radicals or otherwise destabilizing the formulation. It soon became clear that more work on the safety of nanoparticles for sunscreens had to be made public.

So, nanoparticles are already in our products but are they safe? What work has been done so far? How do I know what products contain these particles? These are all questions that are being asked by individual consumers, the scientific community and the wider cosmetics industry. Chatting to one of the nano-zinc or titanium manufacturers would ensure you that work has indeed been done to validate their ingredient’s safety. The ingredient manufacturers have carried out numerous tests into the materials safety in use, manufacturing expose and formulation stability. They assure us (consumers / industry members) that the ingredients have been tested and deemed safe under current health and safety criteria and we believe that to be true. That is why we promote and use these ingredients. However, most of the detail contained within these corporate studies remains proprietary information and is by definition not available for the public. This knowledge gap has created a degree of concern. The CSIRO and Macquarie University are working at filling this gap.

Professor Brian Gulson of Macquarie University and Dr Maxine McCall of the CSIRO, on discovering that a stable isotope of Zinc (Zinc 68) was available via Russian manufacturer Isoflex started work to develop a procedure for tracing nanoparticles of Zinc through sunscreen. The aim of the ongoing study has been to trace and quantify the movement of the zinc isotope after applying it in a standard sunscreen base. For the first time a “real life” scientific study into the fate of nano zinc in sun cream would be made available to the public. This study was formulated to follow the path of nano zinc when applied in a “real life” situation. After an initial calibration and safety trial containing three people a larger trial, including UV exposure and over 20 people was initiated. This was the trial that I took part in.

Volunteers from different walks of life came forward to be part of the trial into nano zinc. My appetite had been whetted during the first of two presentations that Brian and Maxine’s team gave at Sydney’s ASCC lecture evenings. I had been a part of the sunscreen industry for ten years as a supplier and hobby formulator and immediately appreciated the power that this type of study could have. Joining me on my journey were students, shift workers, people just wanting a break and some time out at the beach, travelers both returning and current and others who were closely linked to the study staff. All up, we formed what I believed to be an interesting and diverse group of people, there for different reasons but all happy to put their backs on the line in the name of science!

Leading up to the trial we met up at Brian’s house to have our skin type graded – I am a melanin deficient skin type one (out of a possible six) which means that I don’t usually tan and burn readily (see the Fitzpatrick classification Scale.) While I had realized that my skin burned quickly in the Australian sun, I had hoped that I may had some be a more forgiving two or three as that would make life a lot more convenient. The other volunteers slotted in at various points on the scale with all but the very darkest skin type being present. We were also lucky enough to have a wide range of ages – skin changes as you age and can become dryer and thus a less effective barrier.

For this trial a commercial base sunscreen was put together to mimic as closely as possible a “real life” experience. The standard base was also made up again using the tracer Zinc particles at known quantity. The trial was split into two groups, control (non-nano) and nano (with the tracer zinc). Both groups complied with the same test protocol and both sunscreens contained the 68 Zinc tracer (only in the control sunscreen the tracer zinc was in particles larger than 100nm. Efforts to avoid ingestion were vigorously enforced – washing of hands often, no touching of the sunscreen area, each subject having their own numbered top and towel and all contaminated clothes being taken away each night for laundering.

We could not have been luckier with the weather and venue for the trial. The first day was spent lazing around Macquarie University’s excellent outdoor pool. We had to sign in each day with a urine and blood sample then line up to have our sunscreen applied. Once dosed up we were instructed to wait at least 20 minutes for the cream to settle before we were free to go out and either lie or walk around in the sun for a minimum of thirty minutes. This “lab rat” lifestyle did wonders for our karma as we all enjoyed the luxury of a few hours in the day in which to read, take a nap, talk to friends or cram in some extra study. All in all one could not complain!

The remainder of the trial was spent at North Curl Curl surf club which the clear sunny day that Monday brought was just heaven on earth! The trial routine was simple and repetitive: Urine sample between 9-10am, blood at around the same time, sun cream and specially designed sun top on straight after, wait for 20 minutes and then out you go. The urine sample and sunscreen application was repeated after lunch with a 30-minute sun sit /bathe shortly after. The day finished with the sunscreen being wiped off followed by blood and urine collected at around 3.30. Pretty easy and overall quite painless.

As test subjects, we were exposed to UV light for at least an hour each day and the sunscreen for a minimum of four hours a day over a period of five days – adequate time for a skin reactions to develop or skin penetration to take place if it was going to. The UV readings during the trial were recorded at regular intervals and while Day 1 recorded a moderate UV reading and day 2 was low, days 3, 4 and 5 recorded quite intense UV for most of the day. The only deviation from “normal” sunscreen usage was that we were carefully monitored so as not to ingest any. This after all was a trans-dermal study!

So, with this leg of experimental data collecting over what conclusions can be anticipated? Well, the results and discussion will of course take longer to write than this article. The trial was designed to track the fate of nano zinc through skin when applied in a commercially representative sunscreen. While zinc is present in every body, the careful selection of the rare Zinc isotope will make it relatively easy to pick up should any have got into the blood stream or urine. The ratio of the zinc isotopes in any blood samples will also give a quantitative overview of how much zinc made it into the body. The trial design and care of the panelists should enable Professor Gulson and Dr McCall to conclude that any tracer zinc present was absorbed through the skin rather than being ingested.

This trial has been carefully constructed to look for one thing – dermal absorption of nano zinc in a sunscreen base with UV exposure, that was why the tracer zinc was present in both sunscreens the only difference being the particle size. While the sunscreen base was generic, the trial can’t conclude that nanoparticles of zinc will act the same in all sunscreen formulations. There are many different brands of nano zinc – some are specially coated to prevent agglomeration, others are encapsulated for the same reason and yet more are presented in a pre-dispersion. In addition to that, there are many other products that include a nanozinc sunscreen in their formulation. Anti-aging moisturizers are another proposition altogether due to their complex mix of ingredients targeting the cells within the epidermis and the need for a sunscreen to form a film on the surface of the skin.

Like all scientific studies, this one will not answer all of the questions that surround nanotechnology in sunscreens. What it will do though is give a solid basis from which to develop further testing should funding become available. It may also provide a framework from which the cosmetic industry can develop an industry standard test method. After all, the safety of sunscreens is a health issue and consumer confidence and safety remain of paramount importance. It should also be left as food for thought that should the nano zinc turn up in our urine or blood samples, we should not automatically assume that this is going to do harm. Zinc is often taken as a supplement and is essential in many metabolic processes. It is also essential for the health and vitality of skin cells. However, for Zinc to function as an effective sunscreen agent it does need to be present on the surface of the skin and not taken into it– this is another issue and one that formulators may have to grapple with.

I would very much like to thank Professor Gulson and Dr McCall for putting time, funding, effort and passion into this project and allowing me to be a part of it. Consumers want two things from their sunscreens: efficacy and safety and while the individual ingredient manufacturers have assured us of their nano-ingredients credentials and sunscreen manufacturers comply and often exceed current SPF standards, this publicly funded and managed research makes the information available to the general public. Long live publicly funded science I say!

 NEWSFLASH: 24th February 2010: The preliminary results of the trial are being presented at ICONN today.  I posted a review of the findings here.