Featured photo courtesy of edition88.
In a previous post in this series, I wrote about how the total amount of UV radiation hitting Earth’s surface has not significantly increased, and we are probably getting less UV exposure than in the past. I then wrote about how UV radiation (UVB, specifically) produces vitamin D synthesis in the skin, and how critically important vitamin D is to our health.
I then covered sunburns and skin cancer in this series, and how the majority of skin cancer cases are not life threatening. That post also discussed how UV radiation can be a factor in the development of skin cancers, but it is clearly not the only factor involved in light of the significant rise in skin cancer rates and reduction in UV exposure.
This post will examine the types and use of sunscreen. Sunscreen has been touted as a saving grace of modern preventitive medicine. According to most skin experts, without sunscreen lotions blocking out the ravaging UV radiation emitted by our powerful sun, we would all be getting scorched, aging rapidly, and developing skin cancer. There was even a song in the 90’s dedicated to how great sunscreen is (along with some unrelated, perhaps more prudent advice).
Although the use of sunscreen clearly reduces the incidence of sunburns, and there is some evidence that the use of sunscreen in some populations does reduce the incidence of skin cancers, these studies focus on the non-deadly basal-cell carcinoma (BCC) and squamous-cell carcinoma (SCC) (with only a weak link to BCC). Along with these studies, however, there are contradictory studies that observe that skin cancer rates (focusing on the deadly melanoma) are not significantly reduced by the use of sunscreen. There is even evidence that melanoma rates are higher in sunscreen users as compared to non-users. Sunscreen provides sunburn protection and potentially non-deadly skin cancer prevention (SCC), but does not prevent melanoma, which is the real concern.
This is a complicated subject with numerous contexts, and there is probably not yet enough data to make a definitive decision, but there are some startling observations that can be made. First, let’s examine the different types of sunscreen, then look at some of the consequences of the use of these particular types.
The Different Types of Sunscreens:
There are many different types of sunscreen lotions available. Sunscreen lotions are made up of a myriad of ingredients, but all contain active ingredients that do the actual screening out of the UV radiation. These active ingredients, for the purposes of this article, will be called sunscreens while the sunscreen-containing-lotions will be called sunscreen lotions.
Active ingredients within sunscreen lotions can be divided into two main categories: physical sunscreens and chemical sunscreens. Modern sunscreen lotions usually contain a variety of sunscreens. Both physical and chemical sunscreens will help prevent sunburn, but they do so in different ways. The table below presents the main differences:
Physical Sunscreens vs Chemical Sunscreens
|How it works||By reflecting or blocking UV radiation, aka 'sunblock' or "inorganic sunscreen'||By absorbing UV radiation in the molecular bonds within the chemicals, aka "organic sunscreen" (organic, meaning carbon containing, molecules are used)|
|Active Ingredients||Titanium dioxide (TiO2) and/or zinc oxide (ZnO)||Too many to list, but some notables include: octylcrylene, avobenzone, octinoxate, octisalate, oxybenzone, PABA, etc.|
|UV Spectrum Covered||TiO2 only reflects UVB (burn causing) radiation, and not enough UVA (still cancer causing).|
ZnO covers almost all of the UVA/UVB spectrum.
|Varies by chemical. Generally, in a lotion, several chemicals are used to cover the entire UVA/UVB spectrum, but often there are gaps.|
|Texture and/or Appearance||Chalky, white, thick texture. Both TiO2 and ZnO are particulates meaning they are powders suspended in the lotion. Appears white.||Usually has a runny texture. Colourless and sometimes odourless.|
As shown in the above table, sunscreens do not always cover the entire UVA/UVB spectrum. If you’ll recall from my post on Sunlight and our Atmosphere, UVA radiation does not cause sunburn, but does still damage molecules in the skin and is more deeply penetrating. UVB radiation is responsible for vitamin D synthesis and sunburns. More on this below.
Health Risks of Sunscreen Use:
Some Sunscreens Only Block UVB Radiation, Not UVA
It is well known from this paper and this lawsuit against sunscreen producers that a good number of sunscreen lotions only protect against the sunburn-causing UVB radiation while ignoring the deeply penetrating UVA radiation that makes up the bulk of the UV radiation reaching Earth’s surface. According to the Environmental Working Group (EWG), as many as two-thirds of sunscreen lotions available in the US fit this description. UVA over-exposure can lead to the type of DNA damage that can lead to cancer and photo-aging, and has none of the benefits of UVB radiation (most notably, vitamin D synthesis).
By blocking out UVB with a sunscreen lotion of this type, users can stay out in intense sunlight for much longer periods of time as they will not experience the natural warning sign to regulate sun exposure: the beginnings of a sunburn. In that context, a sunscreen user would presumably be exposed to much more UVA than normal in the absence of UVB. This could give a false sense of security to the sunscreen user that leads to more overall damage with none of the benefits of UVB radiation.
Modern sunscreen lotions are much more likely (not guaranteed, however) to be “broad-spectrum sunscreens” which cover the UVA band along with UVB. Unfortunately, according to the Environmental Working Group, as of 2004 one-third of sunscreen lotions labelled “broad spectrum” were, in fact, not. In 2012, the FDA regulated the use of the term “broad spectrum” to necessitate UVA coverage, so broad spectrum is now indeed as advertised. If you are going to use a sunscreen lotion on a regular basis (which I would only recommend under extreme circumstances), be sure that UVA radiation is also covered.
Some Sunscreens are Carcinogenic/Allergenic/Disruptive
Ironically, sunscreen lotion ingredients, including the active ingredients, while generally promoted as healthy and protective, all come with at least some amount of toxicity concern. Some of these chemicals are carcinogenic (cancer-causing), some cause allergic reaction/irritation in the skin, and some are known to disrupt normal hormonal functioning.
The carcinogenic concerns arise from photodegration of chemical sunscreens. Essentially, when chemical sunscreens absorb UV radiation (notably UVA), they can become reactive oxygen species (ROS) or free radicals. An ROS/free radical can be produced in many ways, but in the context of sunscreen concerns, they are produced when UV radiation breaks a bond in a sunscreen molecule and one of the pieces if the destroyed molecule contains an atom (usually oxygen) that desperately wants to bond with another molecule to regain stability. This ROS/free radical can then bond with DNA or other cellular molecules which causes damage. Although some ROS in the body is natural (used as signalling pathways), ROS in sufficiently high quantities can have many damaging effects, including damage to DNA which is carcinogenic. This paper shows that skin ROS concentrations are higher in users of sunscreen lotions than non-users. Manufacturers now use photostabilizers to mitigate this photo-instability, but the effectiveness remains controversial.
Along with potential carcinogenesis, sunscreen lotion ingredients are known to cause allergic reactions in some individuals. Sunscreen ingredients can also be absorbed into the body through the skin and are able to disrupt the normal progression of hormones, which can lead to many different problems.
Sunscreen Does Not Allow for Healthy Tanning
Melanin is produced in the skin (via melanogenesis) after exposure to UV radiation through the process of tanning. Once sufficient melanin is present, either through constitutive pigmentation (darker skin) or facultative pigmentation (tanning), UV-induced damage is significantly reduced. One study found that synthetic melanin absorbed 99.9% of the UV radiation it was exposed to. Another study found a more realistic 50-75% reduction for human skin conditions. From these numbers it becomes clear that at least part of the role of melanin in our skin is to protect us from too much UV radiation. Tanning is a natural adaptation to sunlight exposure, much like how muscle growth is a natural adaptation to physical stress.
Although both UVA and UVB radiation can stimulate tanning, only UVB radiation causes the type of tanning that prevents sunburns. In that sense, a tan received while wearing UVB-only protective sunscreen lotion (from the transmitted UVA radiation) will not protect against sunburns, but may convey a false sense of security to the user.
Sunscreen Contributes to Vitamin D Deficiency
Since any effective sunscreen lotions contains active ingredients that prevent the transmission of UVB radiation to human skin (UVA notwithstanding), the chronic use of sunscreen lotions can contribute the epidemic of vitamin D deficiency observed in the modern world. Sunscreen applied to human skin effectively prevents vitamin D synthesis. This is a problem.
Some researchers suggest this is irrelevant since only 5-10 minutes of sunlight on the face and hands a few times a week is all that is required to maintain vitamin D levels. However, this is only true for caucasians who are not using sunscreen during the peak hours of sunny summer days. Thus, it is especially concerning that we are advised to avoid the sun during peak hours (10 am to 4 pm), especially in summer (in applicable temperate regions), or at least wear sunscreen if we must be in the sun. Those exact time windows are the only times where UVB radiation is intense enough to stimulate vitamin D synthesis. If sunscreen is being worn during those times (as is recommended), then vitamin D deficiency is inevitable (in the absence of supplementation, which is not ideal).
With all the information presented above, it becomes clear that sunscreen is not necessarily a positive addition in every context. Based on everything I’ve seen, and lots of time to think about it, I’ve come to the following conclusions:
- Sunscreens will prevent sunburns by blocking UVB radiation, no problem
- Healthy tanning should be encouraged
- Sunscreens prevent healthy tanning
- Sunscreens might slow the progression of the non-deadly SCC
- Sunscreens have not been proven conclusively to prevent melanoma
- Despite more sunscreen use and less UV exposure, melanoma rates are increasing quickly
- Chemical sunscreens might contribute to the progression of skin cancers, including melanoma
- Some sunscreen ingredients have not been studied enough to determine their long-term safety
- Sunscreens contribute to vitamin D deficiency
- Moderate unfiltered UVB radiation exposure is to be encouraged
- If sun protection is truly necessary, the safest way is to use clothing. Next safest way is via physical sunscreens. Chemical sunscreens are to be avoided.
- It is preferable to be naturally resistant to the sun than to use sunscreens (and this resistance can be improved in anyone)
Slathering on a bunch of synthetic chemicals to protect us from a natural source of radiation that we have evolved with for millions of years doesn’t make sense. UVB radiation, which is responsible for sunburns and vitamin D synthesis, is clearly a critical nutrient for human health. These rays damage human skin to an extent, but to completely fear these natural rays is illogical.
Although sunscreen lotions are probably becoming less toxic as more is learned about their negative effects, the real question of the day is “Why are people burning so easily?” This study provides evidence that sunburn rates remain high despite active efforts to avoid it. I believe it is our skin that has become weaker; not that the sun is more destructive.
Through my personal experimentation, I have found ways to naturally increase my resistance to the damaging effects of the sun (including sunburn) through behaviour modifications and diet. This way, I can get all the vitamin D and other benefits of sunlight, I get a nice tan to prevent serious burning, and the long-term damage incurred is minimal and manageable. I use no sunscreen and get plenty of sunlight, and it’s no problem. Quite frankly, I am a blue-eyed caucasian (worst case for sun, supposedly), and through the changes I’ve made to my sun exposure habits and my diet, I find that it takes a very (very!) extreme amount of intense sunlight exposure to produce any significant sunburn anymore. When I do get a bit of a burn, the recovery is very fast (1-2 days at worst). This is in contrast with my experiences as a child/teenager where I burned quickly and took a week or more to recover.
That will be the focus of the next post: How to Increase Your Resistance to the Sun. You’ll find these tips incorporate overall healthy living principles, some of which you will have heard of, some of which might be new to you.
For now, thank you for reading. It would be greatly appreciated if you could add a comment or question to the comments section below.