Are sunscreens really harmful?

The use of SPF creams is one of the main strategies for preventing the development of various skin diseases caused by ultraviolet radiation (UV). Despite the increase in the use of skin protection products, the prevalence of some diseases associated with sun exposure, especially malignant melanoma, is still increasing.

In the last century, a huge number of protective compounds have been developed that protect against UV rays. We know several types of electromagnetic radiation. Ultraviolet radiation consists of 3 wavelengths, namely UVA rays, which emit a wavelength of 320-400nm and are not absorbed by ozone, UVB rays in the wavelength of 290-320nm, which are partially absorbed by ozone, and UVC rays, which are stopped by ozone. UVA and UVB rays can pass through the epidermis and cause the formation of reactive oxygen species (ROS), damage to DNA, lipids and proteins, activation of inflammatory intermediates, tissue degradation,..

What types of UV filters are there?

How to protect yourself from UV rays? By using sunscreens that contain cosmetic ingredients called UV filters. There are currently two types of UV filters in use, physical and chemical, which minimize the previously listed effects of exposure to UV radiation.

Physical or inorganic filters absorb, scatter and reflect UV rays, while chemical or organic filters absorb them. The absorbed light is converted by UV filters into heat and infrared radiation. Organic UV filters that absorb UV rays are divided into PABA derivatives (PABA, ethylhexyldimethyl PABA), cinnamic acid derivatives (ethylhexylmethoxycinnamate, octylmethoxycinnamate), salicylic acid derivatives (ethylhexyl salicylate, homosalate), camphor derivatives (3-benzylidene camphor, 4-benzylidene camphor), octocrylene, triazine derivatives (ethylhexyl triazone), benzophenone derivatives (oxybenzone (BP-3), sulisobenzone) and dibenzoylmethane derivatives.

Physical UV filters that absorb, reflect, and scatter UV rays include zinc oxide and titanium dioxide. Sunscreens are usually a mixture of several different organic and physical UV filters, as this provides broad-spectrum protection.

What are the differences between chemical and physical UV filters?

Now for the tricky part of the post, are UV filters really toxic?

I notice that consumers are increasingly aware of how important it is to know what we put on our skin. We have become more selective about products, as well as about the ingredients we want or don't want to be part of our products. I don't know whether to say whether it's good or bad that today we can find almost everything on the internet. Due to various forums and blogs, unsupported by scientific evidence, consumers have started to believe that chemical UV filters are toxic, that they are hormone disruptors, that they block the synthesis of vitamin D and some have drawn conclusions that it is less harmful to get sunburned than to use creams with SPF.

So what if we go and debate all these claims in turn?

"Chemical UV filters are toxic."

What does it mean that they are toxic? The fact is that this statement is striking. I believe that if I didn't explain it now, it would remain in your head until the next time you buy sunscreen and remember that chemical filters are toxic. With such information in your head, you would naturally go and look for an article that supports this theory and I am almost 100% sure that you would find an article that would confirm your assumptions. Or it would confirm your assumptions because you were reading selectively. Well, we will get to that in a minute or so. Whether a substance is toxic depends largely on how we are exposed to it and in what quantities we are exposed to it. A good example is drugs - let's take paracetamol, which is in Lekadol. Paracetamol is great in low concentrations, as it acts as a painkiller and reduces fever - so it has a therapeutic effect. But in high concentrations it becomes toxic. So the dose determines the toxicity of the substance. The same is true for UV filters. UV filters are completely safe for dermal application in concentrations permitted for use in cosmetics.

"UV filters are hormone disruptors."

I absolutely love this statement. There have been a million studies done on UV filters, all with the aim of proving their safety. Remember when I mentioned selective reading a few lines ago? Well, let's see what that looks like. All the data is taken from the same study!

Example 1 – selective reading:

"Many studies have identified ethylhexylmethoxy cinnamate as an endocrine disruptor, as it can interact with the endocrine system at multiple levels. In vivo and in vitro studies indicate that OMC has estrogenic activity, and also affects the amount of testosterone and estradiol."

What do we learn from this section? That ethylhexylmethoxy cinnamate (the most commonly used chemical UV filter, found in 80% of sunscreens on the market) is a hormone disruptor. For someone who is already pretty sure that UV filters are toxic, this is enough confirmation that they will be happy to spread it to their friends and acquaintances. Everyone will avoid ethylhexylmethoxy cinnamate, even though they don't know exactly why and how it is supposed to act as a hormone disruptor.

Example 2 – critical reading:

"Many studies have identified ethylhexylmethoxy cinnamate as an endocrine disruptor, as it can interact with the endocrine system at multiple levels. In vivo and in vitro studies indicate that OMC has estrogenic activity, and also affects the amount of testosterone and estradiol. The study was conducted on rats orally exposed to 57.5mg of OMC per 20g of body weight."

What do we learn from this section? The article continues by telling us that the data comes from a study on rats that were fed enormous amounts of this UV filter. I don't think we eat sunscreen by the spoonful. Is this data even relevant considering that we are only exposed to UV filters dermally? Many studies do indicate a link between the increasing use of cosmetic products containing these compounds and the occurrence of endocrine and developmental disorders. However, we must be aware that most studies report toxic effects of UV filters at concentrations that are significantly higher than those that we can come into contact with in the environment or through the application itself. The studies are mostly done on animals and data from animal studies cannot be simply extrapolated to humans.

"Sunscreens block vitamin D synthesis"

Since the use of sunscreens has increased, they have gained many supporters, but also many opponents. Opponents of sunscreens claim that they block the synthesis of vitamin D, which is essential for our health. There are also extreme opponents who claim that the use of sunscreens is more harmful than unprotected sun exposure.

Vitamin D3 can be produced in the skin when exposed to ultraviolet B (UVB) radiation, so it is possible to increase low vitamin D3 levels with exposure to UVB rays. During exposure to sunlight, radiation with a wavelength of 290–315 nm penetrates the skin. Most of this UVB radiation is absorbed in the epidermis, so when exposed to sunlight, most of the vitamin D3 is produced in the skin, in the living cells of the epidermis.

Now let's calculate that if we use SPF50, it blocks about 96% of UV radiation, right? This means that only 4% of UV radiation can pass through, which greatly reduces the possibility of synthesizing vitamin D. But let's also ask ourselves how much sunscreen do we actually apply to our body? How many areas of skin do we leave exposed, completely unprotected, with the exception of the face? The surface area of ​​the skin on the face is very small and the synthesis of vitamin D on such a small surface area as the face is negligible compared to the body. Let's be realistic, we apply such small amounts of sunscreen to our body that it is questionable whether we have a protection factor of SPF 5. So with SPF 5 we are approximately 80% protected from UVB radiation. This may sound like a lot, but this time as much as 20% of UVB radiation can pass through to the skin! Not to mention the parts of the body that we usually don't even apply sunscreen to. All parts of the skin that are not protected allow 100% transmission of UVB radiation and thus the synthesis of vitamin D, but also an increased risk of skin cancer. The use of sunscreen for daily sun protection does not compromise the synthesis of skin vitamin D, even if sunscreen is used in the intended amounts (2mg/cm2).

The blog was created in collaboration with Cosmedoc.si