TESTING ISO WATER RESISTANCE
comments. These are not necessarily technical but more global comments, such as ‘it is acceptable?’, ‘is it easy to follow?’, ‘does it need to be modified because it’s confusing?’ “With this Committee Draft, if it is accepted, you respond to the comments and see that all of these are answered. Then you jump to the DIS, which is a Draft International Standard. “You draft it again and resend it to the
Technical Committee; you may receive some comments and, as soon as you answer these, you jump to the FDIS, which is the Final Draft International Standard. Here you may have editorial comments, but there cannot be any technical comments at the FDIS stage.” Finally comes publication, whereby the FDIS is validated by the Technical Committee then published by the ISO Central Secretariat in ISO format and translated into French. Ordinarily, the shortest timeframe to progress through all required stages is three years, but, as Pissavini notes, “most of the time you have ring tests to validate some point, or you need to run experiments and that requires around one year”, so the full process often takes four years.
ISO 16217 & 18861: THE SPECIFICS As mentioned earlier, when it comes to the water immersion procedure for determining the water resistance of sunscreen in vivo, historically two methods have commonly been used with the US opting for the FDA method and Europe using the Cosmetics Europe (formerly Colipa) method. Pissavini notes: “These two methods were similar but with some differences… however, they were similar enough to propose an ISO method combining both.”
The publication of ISO 16217 clarifies and harmonises several potential variables, for example, the definition of the spa, which was inconsistent between the FDA and Cosmetics Europe versions. “We decided to harmonise and to give a definition of the spa,” says Pissavini. Other inconsistencies between the pre-existing methods that have been harmonised in ISO 16217 include the sample location – essentially where the sunscreen is placed on the back of the volunteer; the subjects’ position in the spa – whether the volunteers are placed closer to the jet, or further away; and the flow measurement of water into the spa.
“Something which was very important was to define the water,” adds Pissavini. “Because you can have different types of water – salt water, tap water, local water. And we also define the hardness, conductivity, pH and temperature of the water. We had to define the temperature of the air outside too.”
Another aspect was providing a standardised sanitation method, which
54 January 2021
is “perhaps not very important for the SPF, but is very important for the volunteer”. Something Pissavini highlights as being “very important” is the agitation. “Should the agitation be only made by water, or by bubbles, which is water plus air?” he asks. “This could have an effect!”
Dr Marc Pissavini is Research Director at Coty and convenor of ISO’s Working Group 7, which covers sun protection test methods
In the end, “in the ISO method, we defined that the agitation should be made only by water jets – no air. Because you can imagine that, depending on the spa used, some might have bubbles and some might not. But now it is well defined.” Also specified within the standard is the range of the value – something incorporated into all methods – which exists to ensure CROs and test institutes complete their experiments to high enough standards. Likewise, CROs are required to check the standard once every two months. Pissavini reiterates that ISO 16217 is not a “revolution”, but a “fine tune [of] the methodology to find the best compromise between the FDA and the Cosmetics Europe/Colipa methods”, which aims to “reduce all the areas that can lead to variability in the final result”.
Publishing ISO 18861 for evaluating the water resistance retention percentage was a rather simpler process.
As Pissavini explains: “You don’t have to harmonise this, as it’s the calculation of a percentage. It was quite an easy method. We had to define the range of the P2 standard, but that was the only difficulty.”
FUTURE FOCUS
In conjunction with publishing ISO 16217 and ISO 18861, WG7 has been developing or improving several other sun protection test methods in recent months.
One of these was a systematic review of the in vivo SPF method, which “is where we already have an ISO method [in this case published in 2010], but we’ve decided to review and update it”, which was also published last year. “We have also had a revision of the in vitro and in vivo UVA methods, and there are two in vitro SPF methods currently in development at ISO level,” says Pissavini.
These, he says, are especially important, “as we have no alternative method for the SPF in vivo”. The standards, which are being developed in parallel, are for two different testing methods: HDRS (hybrid diffuse reflectance spectroscopy) and SPF PMMA double plate testing. According to Pissavini, the original plan was to publish these SPF in vitro standards in 2022, but the necessity for a ring test means they may be in the pipeline for a little longer.
In the meantime, sun care manufacturers can breathe easy knowing they now have a water-tight option for assessing their products’ water resistance
cosmeticsbusiness.com
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