A term of the total sun protection does not exist any more. As of 2006, higher indexes than 50 were regrouped by the European Commission in one single index of 50 plus. That was undertaken as a measure to protect the consumer against any allegedly wrong assumptions or claims in beliefs that with a sun protector of 80 or 100 you could stay out in a strong sun the whole day without reapplying!
How much to apply? The dose used in FDA sunscreen testing is 2 milligrams on square centimeter of exposed skin. Considering only the face, this translates to about one fourth or one third of a teaspoon for the average adult face.
How often and when to apply? The sunscreen should be applied about 20 minutes before you head out into the sun. More sunscreen needs to be applied after any swimming or sports because no sunscreen is completely water or seat proof, every 2 hours as a minimum.
Ultraviolet rays can be subdivided into three different wavelength bands - UV-A, UV-B, and UV-C. UV-C is most energetic and most harmful;
Luckily, most of UV-C rays are absorbed by the atmosphere thanks to the ozone layer.
UV-B rays energy extends down to the earth's surface and UV-A radiation passes the earth's atmosphere almost unfiltered.
Sun radiation is a source of life on earth but it is also a great danger. Too much ultraviolet light can cause irreversible damage to DNA, it can cause cells to mutate beyond repair, or to die. UV-B are responsible for many of skin cancers. Recent studies strongly suggest that large doses of UVA, too cause premature ageing and may enhance the development of skin cancers.
In particular the UV is dangerous to children, as an increased risk of developing melanoma in adults has been linked to severe sunburns during childhood.
There are numerous factors that can increase health danger of the sun exposure:Low ozone correlates with much UV.
- a 10% decrease in ozone could cause an additional 4500 melanoma skin cancers and between 1.6 and 1.75 million more cases of cataracts worldwide every year.
On cloudy days, UV levels are usually lower. But clouds can also lead to increased UV levels through the scattering effect.
- Sand, snow, and water all tend to reflect UV rays. Snow can reflect as much as 80%, dry beach sand about 15%, and sea foam about 25%.
- High altitudes increase your exposure to the sun radiation. The World Health organization confirms that with every 1000 metres increase in altitude, UV levels increase by 10% to 12%. During a flight you are also subject to a minor irradiation - but that is a different story altogether.
- The closer to the equator, the higher the UV radiation levels.
Staying in shade, wearing T-shirts on the beach, hats with a broad brim, and sunglasses, spending small amounts of time in the sun over a period of several days, to give your skin time to start its own built-in protection against UV rays – AND most important of all: Avoiding the sun between the hours of 11 am and 3 pm during day light saving time can reduce your UV exposure by more than 50%.