The summer is back again. In this sunny time of the year most of us will spend more time outdoors than the other seasons. If you had sun burns last year and determined to do something about it next time, hope you will find this information well.
Sun and UV exposure
Among other things, ultraviolet radiation or UV is the major contributor to the sun burns. If you are not careful and excessively exposed to UV, you might end up with premature skin aging or even worse, skin cancer. The statistics on diseases related to UV exposure is alarming, even though they don’t make headlines most of the time. Each year, more than 2 million people in US are diagnosed with skin cancer. The estimates reveal that the 90% of the nonmelanoma skin cancers, and 65% of melanoma skin cancers are directly associated with exposure to UV radiation from the sun. Although, skin cancers are considered as a relatively easily treatable type of cancer, around 13,000 people die due to skin cancer each year in US. What is more unfortunate is, that these UV related diseases can be easily prevented by using a broad sun protection program.
UV exposure reach to its peak each year during the summer season (May – August) in the US. The exposure is greatest during 10 am to 4 pm when sun is at highest in the sky. This is also the time that most of us decide to spend outside. The UV radiation that we commonly exposed to, consist of two major types; UV A and UV B. Skin damage caused by UV is directly related to the intensity of these two types of radiation and the duration of the exposure.
The trouble with UV
UV A has the deepest penetration and reaches to the middle layers of the skin. This is the type of radiation that dominantly responsible of skin tanning and known to play an important role in skin aging and UV related skin wrinkling. Scientists have found that UV A can initiate DNA damage in the outermost layers of the skin where the most cancers are detected. Tanning of the skin is a desperate attempt by body to prevent further DNA damage. These damaged DNA in cells can result imperfections or mutations which may lead to a skin cancer. UV B is the main cause of sunburns and as a key contributor to the skin cancer. UV B, however, can only penetrate through the outermost layers of the skin. UV B only accounts to 5% of the UV radiation reaches to earth’s surface.
If interested in getting sufficient protection from the sun’s UV, one should pay attention to the broad spectrum protection from both UV A and UV B regions. A commonly employed rating called, Sun Protection Factor (SPF) rates the effectiveness of the sun protection only in UV B range. This rating is especially useful in gauging the effectiveness a skin protection product from preventing sunburns caused by UV B rays. The recommended SPF is 15 or higher. SPF also lets you roughly calculate your maximum recommended sun exposure. If you typically develop sunburns within 10 min of sun exposure, with SPF of 15 you can withstand 150 minutes of sun without a sunburn. It’s also important to note that UPF of 30 wouldn’t necessarily mean that you will get twice the protection. UPF of 15 filters out 93% of UV B, and SPF of 30 would filters out 97% of UV B.
Sunscreens provide the only protection to the unexposed areas of the skin. Some of you may remember about 10-15 years back, sunscreens looked almost like a white paste on the skin. These conventional sunscreens used white pigments like Zinc Oxide and Titanium dioxide to primarily absorb and scatter the UV radiation. These bulkier particles effectively absorb UV light but due to their bigger sizes they largely scatter visible light as well, producing a white color.
Nano sunscreens, presents a class of much improved type of a sunscreen, in terms of UV protection as well as aesthetic performance. These nano sunscreens also contain white pigments like Zinc oxide and Titanium dioxide, but with the diameters in the range of 25 to 50 nanometers. At this size range these particles show extremely high UV absorbance compared to their bulk counterparts. Due to their small sizes, these particles scatter and reflect less amount of light, making them almost invisible.
Nano Zinc oxide sunblock, contains nano sized Zinc oxide particles as the main active ingredient. The UV absorption in Zinc oxide occur due to excitation of an electron from valance band to conduction band in the nanoparticle. Zinc oxide sunblocks are considered to be slightly superior to titanium dioxide sunscreens. The following image summarizes the absorption performance of the Zinc oxide and Titanium dioxide. It can be seen that sunscreen with zinc oxide nanoparticles can be classified as a slightly better broad spectrum sunscreen because of improved UV absorption, particularly in UV A region. It’s also important to note that, far superior performance of these products in comparison to some organic sunblock products which uses organic molecules to absorb UV radiation.
In practical terms, so called physical sunscreens with nano Zinc oxide or Titanium dioxide show higher stability against UV exposure, requiring less reapplication. These products typically considered as low irritant and low allergen materials compared to chemical sunscreens; ones with organic molecules to absorb UV light. Due to low UV absorption properties of organic sunscreens, for best protection, higher buildup of sunscreen material on the body is required. With the exposure to sun, these organic sunscreens may feel slightly rigid and heavy on the skin. But these problems are less experienced with physical broad spectrum sunscreens.
Safety of nano sunscreens
Possibly the most debated question in the sunscreen industry is that whether the nano sunscreen is a safe sunscreen. This is a natural extension of a much bigger debate among industrialists and scientists on whether the nano cosmetics is safe for humans. The concern is, can these particles penetrate the skin due to the smaller sizes and interfere with the natural processes in the body.
One of the best answers ever given to this question was obtained by a review carried out by Therapeutics Goods Administration (TGA) unit of Department of Health of Australian government (High UV exposure is one of the biggest health concerns in Australia throughout the country). The TGA review concluded that the potential for Titanium dioxide and Zinc oxide to cause any adverse effect is primarily depend on the ability of the nanoparticles to reach viable skin cells. To date, the highest weight of evidence suggest that Titanium dioxide nanoparticles will mainly remain on the surface of the skin which is primarily composed of non-viable cells.
Most of the scientists also speak in favor of physical sunscreens primarily due to their superior UV blocking performance. Usually, the UV protection ability of the sunscreen with zinc oxide or titanium dioxide in nano form is around 30 % more than that of a chemical sunscreen. The expert’s argument is, whether one should risk the exposure of the UV- a scientifically proven carcinogen- to an unproven hypothesis on safety which is substantially less favored by the weight of the data at hand.