How much sun is safe? It depends on how darkly you naturally tan and how easily you sunburn. Those of us who burn very easily and never get much color (skin types 1 and 2) should be very careful to minimize our direct sun time. Those who tan darkly (skin types 4 and 5) can tolerate much more, since the pigment responsible for tanning (melanin) protects us to a varying degree. The tan in skin types 1 and 2 yields an SPF (sun protection factor) of only 2 or 4. The tan in skin types 4 and 5 may yield an SPF of over 20. Unfortunately, even darkly tanning persons will become leathery with lots of direct sun exposure over time.
The effects of the sun accumulate in the skin and cannot be removed. It has been estimated that 75% of our lifetime sun dose has been absorbed by the time we're 18 years old! Sunburn is always bad, not only because it looks and feels terrible, but because it increases the risk of cancers of the skin, including malignant melanoma. Protecting our children from sunburn and teaching them about the sun is one of the wisest investments you can make.
How strong of a sunscreen do you need? An SPF of 15 means that it takes 15 times as long to sunburn with screen on than with no sunscreen. Generally, dermatologists recommend a sunblock with an SPF of 15, greater if you're in strong sun or tend to burn easily. Sunscreen absorbs the damaging invisible (ultraviolet or UV) portion of the solar radiation spectrum. Sun Protection Factor only gives information about short-wave (UVB) ultraviolet, mostly responsible for burning. In the near future, standards for protection from longer-wave ultraviolet (UVA), which are more responsible for aging, will become available.
Two-thirds of the most dangerous portion of sunlight, UVB, gets to our skinbetween 10 a.m. and 2 p.m., because the sun is higher in the sky and therefore goes through less of the earth's atmosphere, shich screens UVB. That's why it's safer to schedule outdoor activities in the morning or late afternoon/evening. Simply avoiding direct sunlight during this part of the day will make a considerable impact on how much sun damage your skin accumulates over the long run.
Remember that UVB is reflected by Sand, water, snow, and concrete. Boaters in particular are at risk from reflected sunlight. Also beware of partly cloudy and hazy skies, since UVB penetrates clouds as well. Don't be tricked by how comfortable it feels outside. You can get an awful sunburn on a hazy or overcast day. In addition. lightweight summer clothing may have an SPF of 4 or 6, so you can tan or burn right through your shirt in the direct sun.
