Lifestyle

Broad Spectrum vs PA: What’s the difference?

Posted on : 14.01.2020

With their unpronounceable ingredient names, claims of UVB and UVA protection, water-resistance times and more, sunscreen labels can be difficult to decipher. You may have also noticed that some products are labelled with the term ‘PA+++’, or similar, which looks like some new, mysterious grading system. So, what does PA mean? Is it yet another characteristic you need to consider when buying sunscreen?

 

 PA Explained

The good news is that PA is not as complicated as it seems. In fact, if you live in Australia, you can ignore the PA classification altogether. It is simply another way to score UVA protection (the UV waves that are primarily responsible for photoageing and deeper tissue damage[1] – for more on the difference between UVB and UVA, check out this article ). It was developed in Japan and is used across Asia but PA scores don’t typically appear on sunscreens outside Asia unless the manufacturer sends the same pack to multiple regions. In Australia, UVA protection is captured as part of the ‘Broad Spectrum’ claim, but how does this compare to PA?

 

Broad Spectrum

Since 2012, all Australian primary sunscreens with an SPF greater than 4 must offer broad-spectrum protection, meaning they need to protect against UVA and UVB radiation.[2] In the past, since UVB was considered to be the most dangerous type of UV, sunscreens could offer only token UVA protection and still meet the broad spectrum criteria.[3] We now know that UVA radiation can be just as harmful as UVB,[1] so the new Australian standard requires sunscreens with a higher SPF (UVB protection) to also have higher UVA protection in order to claim Broad Spectrum. Specifically, the UVAPF (UVA protection factor) must be at least one-third of the labelled SPF (UVB protection factor).[4]

 

 PA[5]

PA, which stands for the ‘Protection Grade of UVA Rays’, is an independent UVA protection score. It is based on a method called Persistent Pigment Darkening (PPD), which I won’t go into in detail here, but it’s similar in theory to SPF. While an SPF of 10 means skin can (theoretically) absorb 10 times more UVB radiation before burning, a PPD of 10 means the skin can (theoretically) withstand 10 times more UVB radiation before tanning, or darkening. Here’s how it translates:

PPD = 2 to less than 4 → PA +

PPD = 4 to less than 8 → PA ++

PPD = 8 to less than 16 → PA +++

PPD > 16 → PA ++++

 

 How do they compare?

Let’s consider an Australian sunscreen with an SPF of 50. In order to pass the broad spectrum test, which is a requirement for listing with the TGA, it must have a UVA protection factor, which is equivalent to the PPD value, of at least one-third of 50—about 16.7. This automatically qualifies it for the highest PA rating of PA++++. Naturally, the UVA protection of an SPF 50+ sunscreen would be even higher. The graph below shows how lower SPF sunscreens would compare, assuming they only just met the minimum requirements for Broad Spectrum.

Broad Spectrum works on a scaling system. Any Australian sunscreen with an SPF of 50 or 50+ automatically meets the PA++++ grading.

Figure 1 – Broad Spectrum works on a scaling system. The higher the SPF, the higher the minimum UVA protection (blue bars) must be for the sunscreen to pass. Any Australian sunscreen with an SPF of 50 or 50+ automatically meets the PA++++ grading.

 

Depending on where you are in the world, your sunscreen labels may have different information to display and standards to meet. In the UK, for instance, they use a Boots Star rating to score UVA protection, which is different again. While not all systems were created equal, it’s important to always look for products that offer adequate UVB and UVA protection.

 

When using sunscreen products, always read the label and follow the directions for use. Avoid prolonged sun exposure and wear protective clothing, hats and eyewear to further reduce risk. Frequent re-application is required.

 

[References]

  1. Stiefel C, Schwack W. Photoprotection in changing times–UV filter efficacy and safety, sensitization processes and regulatory aspects. Int J Cosmet Sci 2015;37:2–30.
  2. Australian Government Department of Health Therapeutic Goods Administration. Australian regulatory guidelines for sunscreens (ARGS) [Internet]. 2016 [cited 2019 Jul 26];Available from: https://www.tga.gov.au/publication/australian-regulatory-guidelines-sunscreens-args
  3. AS NZS 2604:1998 Sunscreen products – Evaluation and classification. Standards Australia, Standards New Zealand; 1998.
  4. AS NZS 2604:2012 Sunscreen products — Evaluation and classification. Standards Australia, Standards New Zealand; 2012.
  5. eurofins – Dermatest. JCIA ISO In vivo UVAPF test [Internet]. Available from: http://dermatest.com.au/pdf/JCIA.pdf

 

Contributor: Josh Townley

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