ISO WATER RESISTANCE TESTING
G
iven that so many consumers slap on sunscreen as a precursor to diving into the ocean or a pool, water resistance is a highly in-demand attribute when it comes to sun protection. But, until recently, there was no universal immersion procedure to ascertain water resistance.
Both the US Food and Drug Agency (FDA) and Cosmetics Europe have their own methods, but these subtly differ and there is little way of telling whether these differences have an effect on the results or not.
Therefore, the testing of sunscreen water resistance and its calculation were both ripe candidates for standardised procedures under the International Organization for Standardization (ISO).
ISO 16217, which specifies a procedure of water immersion for the in vivo determination of the water resistance of sunscreen products, and ISO 18861, specifying a procedure for evaluating the water resistance retention percentage, were both published in 2020.
Dr Marc Pissavini, Research Director at Coty and convenor of ISO’s Working Group 7 (WG7: Sun Protection Test Methods) tells Cosmetics Business that work on the procedure for immersion, ISO 16217, began in Paris back in 2015, with work on the second standard, ISO 18861, the calculation of the percentage of water resistance, commencing roughly a year later. “We first needed to make the immersion process and then to calculate, so the calculation was launched a little bit after,” he says. “Why we needed two methods is due to the regulations,” he explains. “Water resistancy is regulated in different ways all over the world. What they have in common is the immersion procedure: everybody should use the same procedure to put people into the water and measure the SPF.
“After that, what you do with this measurement depends on the country. In the US, Australia or New Zealand, to measure the water resistancy, you need to put volunteers in a bath, but you only need to know the SPF after the bath, because the water resistancy is the SPF you have after 40 minutes or 80 minutes in that bath. So, if you start with an SPF50 and you finish with an SPF25, in the US, you will only have SPF25. What is important is to know how to put the volunteer into the bath and all the procedures.” On the other hand, “in Europe, you would do exactly the same: you’d put the volunteer into the bath and follow the ISO 16217, but the calculation is completely different”.
In Europe and UK, as well as in countries including Japan, China, Korea, Taiwan, Mercosur and South
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Africa, what is measured is the percentage difference of the SPF before and after the bath. “In Europe, if after the bath you have more than 50% of your original SPF – so, using the same example, if you start with SPF50 and you have more than SPF25 after the bath – you can claim you are water resistant,” Pissavini explains.
FROM IDEATION TO PUBLICATION Pissavini is keen to stress that ISO does not exist to validate methods. Nor was the aim for ISOs 16217 and 18861 to start from scratch. Rather it was “to find an agreement, a harmonisation” between the FDA and Cosmetics Europe methods. “We refine two methods that already exist and ISO is there to find a compromise and consistencies between both and publish it. The mistake would be to think that ISO is there to undertake research and to validate a method: it’s not.
“Also, you are not obliged to use ISO methods.
It’s a standard where if you want it, you can use it. You don’t have to use water resistancy 16217 to test water resistancy. But most countries will now prefer these official methods to something that you’ve come up with yourself, as it’s much easier to compare ISO methods versus another method. And even if it is not mandatory, most countries and organisations, CROs [contract research organisations], for example, will use it.” The approximately five-year process of taking these standards to publication took place in multiple stages, as Pissavini elaborates. “The first one [stage] is a New Work Item Proposal. Beforehand, there is an earlier stage that is not mandatory called a Preliminary Work Item, which is really a reflection on the subject during which experts working on the standard will assess whether we have enough data, if the method is advanced enough to present it as a new subject at ISO level, etc. “However, the first mandatory level of ISO is the New Work Item Proposal. The committee votes on this and, once we have a New Work Item Proposal Working Draft, it is at this stage that experts from around the world discuss all the technical points. There can be as many as six or seven Working Drafts.” Once WG7’s experts – which includes upwards of 40 individuals representing countries from across the Americas, Europe, Africa, the Middle East, Asia and Australia – think that they have made enough improvements to the method, it can then be presented as a Committee Draft. “We present this to the Technical Committee, which is made up of countries,” says Dr Pissavini. “It’s not experts who vote, it’s countries – France, the UK, the US, Japan, etc. The Committee normally follows what the Working Group proposed, but adds some
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