Sunrise, Sunset…For What Goes in Between, Which Sunscreen is Best?
January 31, 2018
The cold days are almost over, and we are all looking forward to warm, sunny days of spring.
We long for sun: it is essential for living: beneficial for our mood, our body (synthesis of Vit D).
However, UV radiation is responsible for several acute and chronic detrimental effects on human body, and even more on the skin: sunburn, photo-aging and skin cancer.
What is UV radiation and how we get all the benefits of sun and protect ourselves from cancer and photo-aging which is relentlessly pursuing us and becoming an alarming threat.
The incidence of melanoma across all age groups is growing world-wide and, in the USA, alone, 150,000 new cases per year is projected to occur by year 2030.
The incidence of melanoma in children and adolescents has increased an annual rate of 2.5% as documented in the National Cancer Institute (NCI) surveillance. The American Cancer Society estimates that over 10,000 melanoma death occurred in the US in 2016.
What are these damaging sun rays?
UV radiation (UVR) that reaches the Earth’s surface can be divided into UV-B (290-320nm) and UV-A (320-400 nm)
UV-A can be further subdivided into UV-A1, or far UV-A (340-400nm), and UV-A II, or near UV-A (320-340nm).
UV-B (290-320nm) which represents only 5% of the UV radiation reaching the earth’s surface, includes the biologically most active wavelength. UV-B is responsible for sunburn, inflammation, hyper-pigmentation and photo carcinogenesis.
Ultraviolet A: UV-A (320-400 nm) represents 95% of UV radiation reaching the earth surface.UV-A II (320-340 nm), which constitutes 25% of UVA and, has the same effect on skin as UV-B.
UV-A 1 (340-400 nm) is less potent than UV-A II and has a decreased ability to induce erythema but contributes greatly to photo-aging.
UV-A (320-400 nm) is thought to have a larger role than UV-B in photo-aging because it is able to penetrate into the dermis (under skin surface) deeper than UV-B and is, at least, 10 times more abundant than UV-B in the terrestrial sunlight.
Short wave UV-B mainly absorbs in the (outer layer of skin) epidermis by cellular DNA and induce direct DNA damage, sunburn, inflammation, photo carcinogenesis and immunosuppression.
Long wave length radiations in the infrared (IR) range, 50% of total solar energy, contributes to photo-aging by the formation of reactive oxygen species (ROS) and other mechanisms on molecular level, degrading most of type 1 and III dermal collagen.
With repeated sun exposure, the degraded collagen accumulates over time, resulting in clinical photo-aging.
There were 6500 products categorized as sunscreens in the Amazon.com online catalog.
In the cohort study 65 products were evaluated and 40% did not adhere to AAD (American Academy of Dermatology) guidelines by 3 standard criteria: broad spectrum, SP greater than or equal to 30 and water resistant.
The most striking in this cohort was price, which varied by more than 3000% (the media price per one was $3.32, range $ 0.68-$23.47)
In this cohort study purchase decisions were largely based on what was characterized as “cosmetic elegance”.
Clearly, consumers rate the look and feel of sunscreen more highly than its ability to prevent sunburns. This may be due to a lack of understanding of what SPF means.
SPF is the Sun Protection Factor and defined as the dose of UV radiation required to produce 1 minimal erythema (redness) dose (MED) on protected skin after the application of 2 mg/cm2 of product divided by the UV radiation required to produce 1 MED on unprotected skin.
Although sunscreens provide excellent UV-B protection, lack of UV-A protection, particularly UV-A1. No consensus exists about the best method for measuring UV-A protection.
The Critical Wavelength (CW) is determined to be wavelength below which 90% of the total area of the UV absorbance resides. A broad-spectrum sunscreen has CW of greater or equal to 370nm. If protection from UV-A1 (340-400m) range desired, the sunscreen formula should contain either avobenzone or inorganic particulate sunscreen as an active ingredient (zinc or titanium oxide)
It is important for the public to be familiar with FDA oversight of sunscreen products and their labeling.
On June 17, 2011, the FDA issued final ruling on sunscreen products labeling and effectiveness testing for sunscreen products sold in US. For the first time, sunscreen with SPF greater than or equal to 15 are permitted to have displayed on their labels the following claim: “If used as directed with other skin protected measures, (sunscreens) decrease the risk of skin cancer and early skin aging caused by the sun.” The FDA statement allows the claim of cancer prevention only if the SPF greater than or equal to 15 and the product covers a broad range of both UV-A and UV-B rays. However, the AAD guidelines recommend that individuals use a sunscreen with an SPF of at least 30; this recommendation is made on the bases of survey finding that in actualuse, most people apply sunscreens at 0.5-1.0mg/cm2 which is significantly less than FDA recommended amount of 2mg/cm2 when using a sunscreen of an SPF of 15.
For effective, comprehensive photo-protection sunscreens should be used with other sun protection measures and must be re-applied at east every 2 hrs.
The FDA has stated that products with very high SPF values (50+) may create a false sense of security for the public, promoting some to stay longer in the sun.
In 2011 FDA final ruling is very specific that the terms “sun block”, “water proof”, and “sweat proof” are not permitted to appear on sunscreen labels. Labels can only contain statements that they are either water- resistant (40 minutes) or water-resistant (80 min). Sunscreens cannot claim to provide sun protection for more than 2 hours unless they are reapplied.
Simply staying indoors is obviously the best way of avoiding the sun. However, encouraging individuals to time outdoor exposure to avoid the hours when the sun is at its zenith is more practical. Trying to schedule activities before 10 am and after 4 pm (daylight savings time) avoids solar exposure at times of peak intensity. Individuals need to be reminded that on cloudy days as much as 80% of UVR may still penetrate the cloud cover. Shade availability in recreational areas is also desirable despite difficulty in accurately estimating the protective effects with varying reflection and penetration in different environments. Window glass absorbs most of the radiation below 320 nm; however, considerable amounts of UV-A radiation may still pass through glass. Special plastic films containing UV-A shields as an interleaf or overlay are available.
Clothing can be an excellent form of sun protection. The most important determinant is tightness of the weave. Fabric type is less important. Thickness is also less important than regular weave. Protection drops significantly when the fabric becomes wet. Color plays a minor role, with dark colors protecting better than light colors. A crude test of clothing is to hold it up to visible light and observe the penetration. The FDA defines clothing with a SPF rating as a medical device. One approved line of clothing with a rating of SPF 30 or greater is Solumbra (1-800-882-7860). Hats are the most important articles of clothing. A 4-inch wide circumferential brim is required to cover the face and neck.
Because UV light can have both acute and chronic adverse effects on ocular tissue, sunglasses provide important protection. National standards are in place for Europe, Australia, and the United States. Compliance with the standard in the United States is voluntary.
Sunscreen should be applied 15-30 minutes prior to sun exposure to allow sufficient time for a protective film to develop. Sunscreen should be reapplied after prolonged swimming or vigorous activity. Under conditions of continuous UVR exposure, they should be reapplied every couple of hours. Sunscreen needs to be applied liberally. As much as 1 oz may be needed to cover the entire body. Particular attention needs to be paid to the back of the neck, the ears, and the areas of the scalp with thin hair. Sunscreens represent only one component of a total program of photo-protection.
It is advised that everyone protect themselves from UV radiation to avoid the several acute and chronic detrimental effects.
At Carrington Medical Spa we carry a variety of sun care products that can help protect every member of your family.
Call us or stop by today! We look forward to hearing from you!
Yours in good health,
Dr. Liliya Slutsker