Less strong UV radiation also leads to long-term damage
When is it necessary to protect yourself from too much sun? When can the sun cause long-term damage? The current recommendation of the World Health Organization is: If the UV index for the day is above 3, we should use sunscreen and Co.. Researchers from Australia and New Zealand have now shown that even weak UV radiation attacks our skin to a critical extent.
The basics
The UV index, according to Richard L. McKenzie from the National Institute of Water & Atmospheric Research, New Zealand and Robyn M. Lucas from the National Center for Epidemiology and Population Health at the Australian National University, shows when the sun shines so strongly that our skin would be damaged after an hour without protection. Very few people stay outside for an hour or a few when the weather is nice. Time flies by, especially when playing on the playground, on the beach or doing sports.
The type of radiation to which our skin is particularly sensitive is called erythemic UV radiation. It is specified in Standard Erythemal Doses (SED), with light skin types showing damage such as reddening after 24 hours with radiation of 2 to 2.5 SED.
According to the scientists, it has been proven that, after a short period of time, when the UV index value is high, our skin suffers just as much damage as when it is exposed to low-quality UV radiation over a longer period of time. Long-term damage also occurs when there is less sun. The dosage must therefore always be viewed in relation to the duration.
That was investigated
In their investigation, Richard L. McKenzie and Robyn M. Lucas looked at how the UVI and the SED interact.
The two scientists and their teams compared the specified UV index for the city of Lauder in New Zealand with Melbourne in Australia and other cities and analyzed how the corresponding SED developed over the course of the day.
The results
For the investigated location of Lauder, the SED fell below the safe value of 2.5 for fair-skinned people on only one day, although the number of days on which the UVI was given as below 3 was far higher. Even with low UVI, the SED value could rise to over 14 over the course of the day.
McKenzie and Lucas compared this to cities in other latitudes to rule out that it was a local phenomenon. They found that the relationship between UVI and SED is like this everywhere.
Long-term damage in weak sun: what does it mean?
On days when the peak UVI value remains below 3 but the SED daily dose rises well above the threshold value, exposed parts of the body such as the neck and face are particularly at risk because we underestimate the strength of the sun and risk long-term damage. The study states that in areas in the middle latitudes, i.e. here in Europe, people have to be particularly careful. In the winter months, our UV index is usually not only below 3, but even below 1. The SED also rarely rises above 2.5. In spring or autumn, when the sun is already stronger, we don't take sun protection very seriously. But the dose of UV radiation that we expose our skin to during these transitional phases is, according to the research team, three times higher than on days with high UVI, when sunscreen and protective measures are a matter of course for many. This ignorance increases our risk of skin cancer many times over.
Well thought-out protection, even when there is little sun
McKenzie and Lucas therefore recommend that you do without any indications that with a UVI below 3 no protection is necessary and, in addition to the radiation dose, also include the radiation output in the form of the SED value. They suggest replacing this information with behavioral recommendations that address when we should be in the sun, how long and with what protection during the day.
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