My SPF Discovery

Last week I worked as a Student Ambassador at a ChemWorks Nano Challenge event day, held at the university for Year 10 pupils from five different schools across Nottingham. Their challenge was to create their own ‘chemical free’ suncream and compare this to commercial SPFs to evaluate what SPF number their own was.

During one of the talks that day, I was intrigued by the discussion on SPFs and ultra violet protection. I didn’t realise that there is huge confusion over the labels on sun creams. I was 100% one of the statistic; one in five people are unaware that the SPF rating does not mean protection against all sun damage – only that from UVB rays.

UVB is donated by the SPF number or factor on the front of a bottle, protecting against tanning and burning of the skin. However, UVA rays has its own separate rating system. Ultraviolet A rays are the ones that cause skin-ageing and wrinkles. Both UVB and UVA rays from the sun can cause skin cancer, but UVA is more damaging to long-term health.

I discovered what SPF actually means in terms of UV. SPF 15 means that 1/15 of UVB rays reaches the skin and SPF 30 results in 1/30 of UVB penetrating the skin. Therefore an SPF of 15 absorbs 93.3 percent of UVB rays, but an SPF of 30 absorbs 96.7 percent. The SPF number has doubled, but the absorption rate has increased by only 3.4 percent. Therefore when the SPF number passes 50, the difference becomes insignificant.

We were likewise shown an experiment in an attempt to demonstrate this in a very simple way. A glass bottle filled with water was held up as a UV light was shone on it; the light penetrated straight through and could be seen very clearly on the wall opposite. A commercial SPF 10 was smeared onto one side of the bottle and the light could still be seen but not as vividly. However when repeated with a SPF 50, the same light was almost invisible on the opposite wall; it was very faint if it could be seen at all. This showed me just how much sun creams actually do work and how important they are for protection against the rays.

Having discovered this, I really feel that we should not have to pick our way through complicated dual ratings information to understand how sunscreen works. Before this talk from one of the chemistry lecturers, I was very much unaware that there are also ultraviolet A rays (UVA) to consider too, which penetrate the skin more deeply. It is said that only one in three people check the UVA star rating when buying sunscreen.

I will definitely be analysing bottles with a closer eye from now on. We need to all look for the level of UVA protection which is shown by a UVA star rating or the letters UVA inside a circle, as well as the typical UVB protection rating. The UVA star rating ranges from nought to five and indicates the percentage of UVA radiation absorbed by the sunscreen in comparison to UVB.

I really feel that sunscreen manufacturers should start to provide one easy to understand rating, based on a simple description of the total amount of sun protection offered, such as low, medium, high and very high protection. I still find it shocking that only 8% of people know that the SPF rating on the product label refer to protection from UVB rays only. I also discovered that one in four do not know what the SPF rating stand for at all.

During the talk, we were similarly told that we are simply not applying enough lotion to our bodies to gain the protection level that the bottle suggests. Cancer Research UK recommends applying two tablespoons of sunscreen every two hours when out in the sun in the UK. I know that I definitely do not always use this amount! I just assumed that as long as it is applied evenly over all the skin, it doesn’t matter how much it is.

I must say that I always aim to stick to the shade and cover up when out in direct sunshine between peak sun times. This is largely due to fear of burning! I always come back off holiday as pale as I went, but this no longer bothers me; I’d rather be pale than risk my long-term health from obtaining a tan.

Overexposure to ultraviolet radiation is the main preventable cause of skin cancers. It is estimated that 86% of melanomas in the UK every year are linked to too much exposure to sunlight and sunbed use. Please be careful in the sun and check your SPF bottles closely!


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