Skincare with Friends Ep 75. What UVA Radiation Does to Your Skin

Prepare to have your mind blown (or be bored to death depending on how you feel about intricate descriptions of the cellular responses to different wavelengths of radiation). This episode is about Ultraviolet A protection, how sunscreens are not created equal and how to pick a decent product. Check out our post on no white cast sunscreens.

UVA vs UVB Wavelength

Ultraviolet radiation is part of the electromagnetic radiation spectrum. Light, microwave rays, X rays, infrared and radio waves are all part of the electromagnetic spectrum. This radiation has different characteristics depending on it’s wavelength and energy. 

The lower the wavelength, the more dangerous and cancer causing the radiation is to human beings. UVC (100-289nm), UVB (290–320nm) and UVA (320–400nm) rays have a wavelength lower than visible light and higher than X rays on the spectrum. 

Ultraviolet radiation comes from the sun and tanning beds (and arc welders). Lots of UVC and UVB rays are absorbed by the ozone layer but UVA rays pass right through it. UVA used to be thought of as safer than UVB as it has a higher wavelength, but there is evidence now to show that it can cause cancer. Experts were aware it had the effect of aging the skin but studies on hairless mice in the early 2000s (Di Gruijl, 2000) showed that UVA has cancer causing capabilities. It is now a requirement that sun protection products have UVA protection as well as UVB. 

What are the Effects of UVA Radiation? Do I Really Need to Worry About It?

Yep.

UVB is far better known for it’s threat, because it causes burning and melanoma and we’ve long been aware of it’s risks, but UVA is UVA’s evil little sister. 

• UVA radiation has a longer wavelength of 320-400nm which means it can pass through more stuff. It passes straight through the ozone layer and clouds and windows, so a lot more (20x more) UVA reaches your face than UVB. 
• UVA makes up 95% of the radiation that makes it’s way to earth from the sun. 
• Another point is that the threat of UVA radiation is present for more of the day, in the morning when it hasn’t reached midday heat, there is the risk of UVA. 
• UVA radiation is present in similar amounts regardless of the time of year (so it makes sense to have an easy to wear spf that you wear all year with great UVA protection for aging prevention)
• UVA’s ability to penetrate through things includes the skin. It can reach through the upper layers of the skin into the deeper dermis to cause it’s damage.
• It’s more insidious than UVB. UVB hurts you, you can feel it burning you. UVA doesn’t feel like anything but it’s still having a negative effect. It gives people a false sense of security

UVA radiation has a few different negative effects, including the creation of reactive oxygen species. Reactive oxygen species are unstable molecules which barrel about causing havoc. Havoc like damaging cells and DNA, potentially causing aging and maybe even cancer. And it doesn’t even feel like anything.

“After absorbing UV radiation, a molecule may become altered (damaged) and/or affect (damage) other molecules, e.g., by producing reactive oxygen species (ROS). Thus, UV radiation, especially in the short wavelength range, forms a direct threat to the stability of unprotected organic molecules, which are essential to life on earth: foremost, DNA with aromatic rings in all of its bases”

(de Gruijl, 2000)

UVA’s laundry list of crimes includes-

• Erythema (sun burn)
• Persistant pigment darkening and lentigos (sunspots)
• Sun related (and sunbed) related aging
• Non melanoma cancer like squamous cell carcinoma
• Solar elastosis (loss of elasticity leading to deep creases and crepiness) 
• Actinic keratosis (scaly patches of thick skin caused by sun exposure)
• Immunosuppression in the skin
• Worsening melasma (I found a study which also implicated blue light in worsening melasma, Alcantara, 2020)

 All that being said, we don’t want you to end up like the people we talked about in our last podcast, afraid of the light of day. The body has mechanisms to prevent damage, we have evolved to live under the sun. Our skin has it’s own antioxidant systems to mop up free radicals and creative oxidative species (superoxidase dismutase of NIOD fame is one). And tanning is the skin’s way of preventing UV from damaging us. Also UVA is essential for Vitamin D creation, which we absolutely need. The purpose of this podcast isn’t to make you afraid of the sun, but to help you to find a way to make sun exposure safer. 

How to Know if a Sunscreen is Good at Protecting Against UVA Radiation

Creating a sunscreen is a minefield-

“The development of sunscreens brings along many technical and toxicological issues, which stem from the requirement of having contrasting ingredients for opposite needs in the same formula. Good spreadability is in contrast with water resistance, and the proper level of filters is in contrast with the quality of the texture and solvents needed for product stability. 

Once a potential solution is found for these issues, the development process of a new product is usually further complicated by marketing and regulatory issues. Many useful and practical – and in fact safe – ingredients cannot be used due to a bad reputation they have in web-based blogs and forums or simply because there has been scare mongering, which leads the developer to avoid parabens, alumina and nano ingredients. The other side of the coin is the burden of regulations that classify sunscreens in very different ways in different areas of the world.“

(Pirotta, 2015) 

Further complicating matters is the lack of consistency in the way different countries legislate sunscreen. Because the concerns around UVA are relatively new, there is no consensus on the best way to convey levels of UVA protection to consumers. Some countries do better than others. USA particularly is falling short.

There are a few different ways of assessing a sunscreen’s ability to protect the skin from UVA and different countries go by different measures. There is no global consensus on the best way to assess UVA radiation protection, there are issues with all of them. A good method would need to be reproducible, assess across the whole range of the UVA spectrum and also assess photo stability. I’ll briefly go through them- 

Critical wavelength- is defined as the wavelength at which 90 percent of the formula’s UV absorbance occurs. A basic assessment that demonstrates a product has some protection in the UVA range

UVA-PF/PPD-PF— Often used interchangably. Assesses the ability of a sunscreen to protect against darkening of the skin (particularly useful for melasma sufferers)- if the PPD is 16 it will take 16 times longer to tan after contact with UVA

The UVB/UVA protection ratio- Because UVB is more risky than UVA, this measure assures that the product has the right balance of protection

Different Ways to Assess a Sunscreen’s Ability to Protect Against UVA Radiation

Critical Wavelength

Critical Wavelength is defined as the wavelength at which 90 percent of the formula’s UV absorbance occurs. Sunscreen products and individual filter ingredients have their own absorbance from 290 to 400 nm. I don’t know if that statement makes sense to you, it doesn’t immediately sink in to my brain to be honest. If you have a look at a graph which shows wavelength plotted against absorbance it makes more sense, it basically means that a sunscreen with a critical wavelength of 370nm has protection across more of the UV spectrum. 

Sunscreen products and individual filter ingredients have their own absorbance spectrum and the absorbance spectrum of single ingredients differs depends what it is dissolved in. Until researching this, I didn’t realise how difficult making a sunscreen is. Surely you just pop in your known sunscreen filters into a good base at the right percentage and you’re gold, this is not at all the case, it’s really complex. That is why I would rather rely on a product that is formulated specifically not just whatever spf is in your foundation.

UVA Protection Factor

The UVA number (sometimes UVAPF number) is a description of how protective a sunscreen is against UVA radiation. 

The UVA number can also be determined in vivo (human testing) with persistent pigment darkening or PPD (Kind of Stephen). I find it difficult understanding if indeed UVA-PF and PPD-PF are different things. I think they’re pretty similar measures.

PPD PF- Persistent Pigment Darkening Protection Factor AKA PPD

‘PPD-PF’ and ‘PPD’ both mean the same thing- Persistent Pigment Darkening The PPD method uses human skin (Fitzpatrick 3-5) and assesses how much radiation it takes to cause persistent darkening of the skin after 24 hrs. It is expressed as a number and the higher the better but generally. PPD-PF is the ratio of the minimal UVA dose required to produce PPD if the skin is not protected to the dose required when the skin is not protected-

	PPD-PF	%age UVA protection
PA +	2-4	50-75%
PA ++	4-8	75-87.5%
PA +++	8-16	87.5-93.5%
PA ++++	16 and upwards	93.5% and upwards

This method is preferred by Asian countries. “It has been demonstrated that when using this protocol the results are reproducible for a wide range of products and UVA protection levels” (Moyal, 2010). But it only measures one variable- how well the product protects against tanning and doesn’t assess the sunscreens ability to protect across the whole spectrum. It doesn’t give meaningful information about what is going on from 250-400nm, the longer wavelength UVA rays. These longer wavelength UVA rays do not produce a response that can be observed, but are the cause of solar aging and likely melanoma induction.

What to Look for on Your Sunscreen Label- How Different Countries Display UVA Protection

When it comes to UVA protection, the higher the better. Higher spf values don’t necessarily mean good UVA protection. UVA protection is labelled in different ways in different countries, so there is no singular UVA score like there is for UVB. There might the ‘++++’ or stars or UVA in a circle or simply the term “Broad Spectrum” on the label.

Different countries have different ways of assessing UVA protection and different requirements for minimum UVA protection in products. We are going to compare these requirements and this will give us an impression of how safe you can feel relying on the standards in your country.

How Europe Labels UVA Protection

Critical Wavelength of 370nm and UVA protection must be 1/3 of the UVB protection

Countries in the EU, New Zealand, some of the Middle East/Arabic countries, Turkey and ASEAN countries (Brunei, Myanmar, Cambodia, Indonesia, Laos, Philippines, Singapore, Thailand and Vietnam follow these regulations-

• Sunscreens are considered cosmetic products
• Sun protection factor (SPF) 6 against UVB
• UVA protection factor of 1/3 of the sun protection factor and a critical wavelength of 370  nm. If a product complies, the company can display a UVA circled logo.
• Regarding labelling- the following and similar claims are banned: ‘sun blocker’, ‘total protection’, ‘all day prevention’, as they imply that the product can protect against all UV radiations and that there is no need for re-application, which is not true. There should be instructions for use- (regular reapplication is necessary, keep babies out of the sun…)

“Sunscreen products should be sufficiently effective against UVB and UVA radiation to ensure a high protection of public health. To this end, a sunscreen product should provide a minimum UVB and UVA protection. An increased sun protection factor (i.e. mainly UVB protection) should include an increase in the UVA protection as well. Therefore, the protection against UVA and UVB radiation should be related. Scientific findings show that certain biological damage to the skin can be prevented and reduced if the ratio of the protection factor measured in the persistent pigment darkening test (i.e. addressing mainly UVA radiation) is at least 1/3 of the factor measured by the sun protection factor testing method (i.e. addressing mainly UVB radiation). Moreover, in order to ensure a broad protection, dermatologists recommend a critical wavelength of at least 370 nm.”

From the Official Journal of the European Union Commission Recommendation
of 22 September 2006

There is also the Boots star system– Created by Brian Diffey. The Boots star system rates UVA protection in terms of the ratio of the UVA to UVB absorption of a sunscreen. The labortory test compares the ratio before and after UV exposure, so it also takes into account the sunscreen’s photostability.

	Before UV 0.6 to 0.79	Before UV 0.8 to 0.89	Before UV 0.9 and over
After UV 0.57 to 0.75	* * *	* * *	* * *
After UV 0.76 to 0.85	* * *	* * * *	* * * *
After UV 0.86 and over	* * *	* * * *	* * * * *

How USA Labels UVA Protection-

Critical Wavelength of 370nm

• Sunscreen is categorised as an over the counter drug and is regulated by the FDA
• As spf is treated as a drug, the FDA requires more stringent testing on spf ingredients meaning that newer spf ingredients that are available in europe, are not in the US. Such as Tinosorb
• Re UVA protection- a sunscreen must have a critical wavelength of 370nm to be able to display the words “Broad Spectrum”. Having a particular ratio between UVA and UVB protection isn’t a requirement in the US

Most of the products on the American market meet with US standards for UVA protection but nearly half of those do not meet European standards (Wang, 2017)

The downside of the Critical wavelength as a standard for assessing UVA protection is  that a critical wavelength of 370nm doesn’t ensure high strength UVA protection. Check out these 2 graphs-

There is also the issue that USA is behind in terms of spf ingredients. A lot of the newer UVA protective filters are not allowed to be used by American skincare companies- filters like Tinosorb S, Meroxyl and Ecamsule. It sounds like the FDA is working on a new document about sunscreen ingredients (https://www.clearya.com/blog/safe-sunscreen-filters-according-to-science) it doesn’t sound like they are going to approve more ingredients though, they may even ban some of the ones that they approved before eg Oxybenzone and Octinoxate.

Nadim A. Shaath, a chemist who heads Alpha Research & Development, a cosmetics consulting firm, agrees.

“If we do not change a fundamental mind-set at the FDA,” he says, “I am afraid that no new UV filters will ever be introduced into the U.S. unless through the lengthy, tedious, expensive, and severely restrictive New Drug Application process.”

(Reisch, 2015) 

I would consider buying spf from somewhere else.

How Canada Labels UVA Protection

Critical Wavelength of 370nm

Use the Critical Wavelength 370nm measurement to demonstrate “Broad Spectrum” on their spf products, similar to USA. But there isn’t the same restrictions on ingredients, so Canadian spf can contain the newer UVA filters like Tinosorb and Mersoxyl.

How China, Korea and Japan Labels UVA Protection

Persistent Pigment Darkening Protection Factor

Measured PFA= Labelled PA

	PPD-PF	%age UVA protection
PA +	2-4	50-75%
PA ++	4-8	75-87.5%
PA +++	8-16	87.5-93.5%
PA ++++	16 and upwards	93.5% and upwards

How Australia and New Zealand Labels UVA Protection

Critical Wavelength of 370nm and UVA protection must be 1/3 of the UVB protection

The TGA regulates therapeutic sunscreens. These include:

-primary sunscreens – sunscreens used for protection from UV radiation that have a rated sun protection factor (SPF) of 4 or more

-secondary sunscreens – insect repellents with sunscreen with an SPF of 4 or more and moisturisers with sunscreen with an SPF greater than 15.

They are distinguishable from cosmetic sunscreens because they have an AUST L number on the label, meaning they are ‘listed’ on the Australian Register of Therapeutic Goods (ARTG).

(https://www.tga.gov.au/sites/default/files/australian-regulatory-guidelines-for-sunscreens.pdf, 2021)

Sunscreens with spf above 15 are regulated by the TGA (the Therapeutic Goods Administration) as therapeutic products and go through rigorous testing as well as complying with Standards Australia guidelines. To display “Broad Spectrum” they must pass both the critical wavelength >370 nm and UVAPF/SPF ratio >1/3 tests. 

References

Battie C, Verschoore M. Cutaneous solar ultraviolet exposure and clinical aspects of photodamage. Indian J Dermatol Venereol Leprol 2012;78:9-14

Alcantara, G. P., Esposito, A., Olivatti, T., Yoshida, M. M., & Miot, H. A. (2020). Evaluation of ex vivo melanogenic response to UVB, UVA, and visible light in facial melasma and unaffected adjacent skin. Anais brasileiros de dermatologia, 95(6), 684–690. https://doi.org/10.1016/j.abd.2020.02.015

Reisch, M. (2015) After More Than A Decade, FDA Still Won’t Allow New Sunscreens

Official Journal of the European Union Commission Recommendation of 22 September 2006 https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32006H0647

Cole, 2014 Clinical Concepts About Sunscreens https://assets.bmctoday.net/practicaldermatology/pdfs/0414_insert2.pdf

de Gruijl FR. Photocarcinogenesis: UVA vs UVB. Methods Enzymol. 2000;319:359-66. doi: 10.1016/s0076-6879(00)19035-4. PMID: 10907526.

Hedayat, K., Nasrollahi, S. A., Firooz, A., Rastegar, H., & Dadgarnejad, M. (2020). Comparison of UVA protection factor measurement protocols. Clinical, Cosmetic and Investigational Dermatology, 13, 351.

https://kindofstephen.com/sunlabels/

Moyal, D. (2010). UVA protection labeling and in vitro testing methods. Photochemical & Photobiological Sciences, 9(4), 516-523.Moya

Pirotta, Giulio. (2015). An overview of sunscreen regulations in the world. H&PC Today. 10. 17-22. 

Wang SQ, Xu H, Stanfield JW, Osterwalder U, Herzog B. Comparison of ultraviolet A light protection standards in the United States and European Union through in vitro measurements of commercially available sunscreens. J Am Acad Dermatol. 2017 Jul;77(1):42-47. doi: 10.1016/j.jaad.2017.01.017. Epub 2017 Feb 24. PMID: 28238452.