Vintage tiles advertising Yodamina sunscreen in Cadiz |
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Wear Sunscreen in Andalucía
"Ladies and Gentlemen of the class of '99 Wear Sunscreen. If I could offer you only one tip for the future, sunscreen would be it. The long-term benefits of sunscreen have been proved by scientists." **
Sunscreen is also known as sunblock and suntan lotion. It is a lotion, cream, spray or gel that absorbs and reflects some of the sun's ultraviolet light (UV) radiation and helps protect against sunburn.
Two adjacent bands of the sun's ultraviolet radiation are known as UV-A (315 to 400 nm) and UV-B (280 to 315 nm). UV light is just off the visible spectrum, so it cannot be seen directly by humans.
UV-B mostly affects surface of the skin and is a primary cause of sunburn. Happily, it is mostly absorbed by the ozone layer.
UV-A rays penetrates deep into the skin and have more recently been shown to cause melanoma and squamous cell carcinoma skin cancer, as well as the breakdown of deep skin DNA and structure, which is common symptom of aging.
Minimising UV damage is especially important for children and fair-skinned people and those not accustomed to the strong Andalucian sun.
Andalucía is located 35 degrees north of the equator: on a clear winter day the UV index will be 5 to 7 and in the summer 7 to 9, and exceptionally 10. In the United Kingdom the UV index rarely exceeds 7.
History of Sunscreen
Early civilisations used a variety of plant products to help protect them from sun damage: olive oil, extracts of rice, lupine and zinc oxide paste. Synthetic sunscreens were first developed in 1928. In Europe the first major commercial product was introduced to the market in 1936 by Eugine Schueller, founder of L'Oriel. In the USA Red Vet Pet (red veterinary petroleum) was a physical blocker, a sticky substance similar to petroleum jelly issued to US servicemen on Pacific duty in World War II. Coppertone improved and commercialised the product in the 1950s.
In 1946 the Swizz chemist Franz Grieter was sunburned climbing PizBruin and began a quest to introduce a cream. In 1974 Grieter adapted earlier calculations and introduced "sun protection factor" (SPF), which became a world standard.
Minimal Erythemal Dose
This is calculated from the UV energy equivalent of 1 MED (Minimal Erythemal Dose). This is an effective UV dose that causes a perceptible minimum reddening/tanning of previously unexposed human skin. Naturally, it varies from person to person depending on their skin type.
| Category | Effectivness |
|---|---|
| Category 1: (burners) | <300 J m-2 effective |
| Category 2: (tanners) | 600 J m-2 effective |
| Category 3: (naturally brown) | 800 J m-2 effective |
| Category 4: (naturally black) | 1000 J m-2 effective |
Sun burning time is the maximum time you can stay unprotected without receiving sunburn.
Sun Protection Factor - SPF
SPF is a measure of the fraction of the sunburn-producing UV-B rays that reach the skin. SPF25 means that one-twenty fifth of the burning rays will reach the skin, and the sun burning time to reach the MED can be multiplied by the SPF.
A dose of two milligrams per square centimetre of skin is used to calculate the SPF. Higher-factor sunscreens do not last or protect any longer than lower-factor creams and must be re-applied, usually every two hours.
SPF of 30 is not twice the protection of SPF of 15 but instead a 97% reduction rather than a 93% reduction.
To avoid customer confusion EU has label restrictions. Labels can only claim up to SPF 50+ due to lack of evidence that a higher factor provides higher protection.
UV-A protection
SPF is an imperfect measure of skin damage or ageing as it does not measure UV-A, which does not cause reddening and pain. Conventional sunscreen blocks little UV-A. Some products labelled "Broad Spectrum UV-A / UV-B" protection have not provided good UV-A protection either.
In EU there is a requirement to provide a minimum level of UV-A protection in relation to the SPF. This should be a UV-A protection factor of at least one-third of the SPF. This permits the sunscreen to carry the UV-A seal, which comprises the letters "UV-A" in a circle. This should be a minimum purchase requirement for any traveller.
In the UK Boots the chemist developed a star rating system that has been widely adapted. One-star products offer the lowest ratio of UV-A protection and five-star products the highest. The star system refers to the ratio between UV-A protection and UV-B's SPF, so not all five stars are equal.
Application of Sunscreen
A dose of two milligrams per square centimetre of exposed skin. An average adult 1.63 metres tall and weighing 68 kilograms with an 82-centimetre waste, wearing a bathing suit covering the groin area, should apply 30 millilitres evenly. This is a golf ball sized amount. Covering only the face is one-third of a teaspoon. Studies have shown that most people only apply a quarter to a half of this amount. If so the effectiveness should be downgraded by the same factor.
Assunscreen needs to be re-applied every two hours, or five times during a full day's sunbathing, that would require the procurement of 150 millilitres a day per person of sunscreen. This is most of an average sized (200-millilitre) bottle.
Sunscreens are no longer allowed to be marked "waterproof" but instead must be labelled "water resistant".Thismeans that the sun cream still functions when wet and NOT that it does not need to be re-applied on leaving the water. In the USA water resistant means protection must last for 40 minutes in water immersion. It must still be re-applied, usually every two hours. Which's tests* in the UK found that the SPF dropped by 59% after 40minutes in saltwater.
Choosing Sunscreen
Mineral-based sunscreens based on zinc oxide or titanium oxide sit on top of the skin and reflect the UV. They tend to leave a whiter chalky layer on the skin. The more expensive the cream, the less visible this layer.
Chemical-based sunscreen based on oxybenzone, retinyl palmitate, octocrylene and octinoxate seeps into the skin and absorbs the UV. Some studies link these chemicals to hormone imbalance and others do not. Others demonstrate damage to coral reefs, and as such oxybenzone is banned in Hawaii.
Which Magazine* tests found that all but one demonstrated the SPF claim irrespective of price, and concluded, "the only value of more expensive products is that they are cosmetically more appealing".
It is worth noting that children's sunscreens in the UK are exempt form VAT.
Fabrics protect
Fabrics have a similar factor called ultraviolet protection factor or UPF. UPF 30 is typical for protective fabrics and UPF 6 for standard summer fabrics.
To continue reading about the UV index of sunscreen, click here.
*Which Magazine sunscreen Review
**Mary Schmich's column was published in the Chicago Tribune on 1 June 1997. The essay, giving various pieces of advice on how to live a happier life and avoid common frustrations, spread massively via viral email. The essay became the basis for a successful spoken word song released in 1999 by Baz Luhrmann, also known as "The Sunscreen Song" and later to become a popular slide show video with 15 million views on You Tube.