What are UV Rays?
UV Rays (ultraviolet rays) are a form of energy that is classified as a type of electromagnetic radiation. Other forms of electromagnetic radiation include X-rays, visible light, infrared rays, and radio waves. UV rays have a smaller wavelength than visible rays and thus have a higher energy content.
Where do UV Rays Come From?
The sun is a major source of ultraviolet rays. Though the sun emits all of the different kinds of electromagnetic radiation 99% of its rays are in the form of visible light, ultraviolet rays and infrared rays (also known as heat). Man-made lamps can also emit UV radiation and are often used for experimental purposes.
What do UV Rays Do?
Ultraviolet rays often carry the unfortunate circumstance of containing too much energy. For example, infrared rays create heat in much the same way as rubbing your hands together does. The energy contained in the infrared rays causes the molecules of the substance it hits to vibrate back and forth. However, the energy contained in ultraviolet rays is higher; so instead of just causing the molecules to shake, it actually can knock electrons away from the atoms or causes molecules to split. This results in a change in the chemical structure of the molecule. This change is especially detrimental to living organisms as it can cause cell damage and deformities by actually mutating its genetic code.
What is the Difference Between UVA, UVB and UVC Rays?
Ultraviolet rays can be subdivided into three different wavelength bands, UVA, UVB and UVC. This is simply a convenient way of classifying the rays based on the amount of energy they contain and their effects on biological matter. UVC is most energetic and most harmful; UVA is least energetic and least harmful.
Luckily, UVC rays do not reach the earth’s surface because of the ozone layer. No UVC rays from the sun come into contact with life on earth though man-produced UVC rays can be a hazard in certain professions such as welders.
UVB rays have a lower energy level and a longer wavelength than UVC. As their energy is often not sufficient to split an ozone molecule, some of them extend down to the earth's surface. UVA rays do not have enough energy to break apart the bonds of the ozone, so UVA radiation passes the earth's atmosphere almost unfiltered. As both UVB and UVA rays can be detrimental to our health, it is important that we protect ourselves.
What Factors Influence the Variability of UV Radiation?
UV levels are not constant over the course of a day or even over the course of a year. Factors that influence the level of UV rays in the atmosphere include the position of the sun in the sky, the amount of ozone present, clouds and weather. Note usually UV levels are lower during cloudy skies as clouds can deflect rays up into space. Clouds can, however, also lead to increased UV levels. This happens, for example, when the sun is not obscured by clouds but clouds in the vicinity of the sun reflect additional radiation to the ground. Additional factors that influence UV levels include altitude (the higher you go, the higher the UV levels due to a thinner atmosphere) and the physical features of your surroundings. Snow, sand and water can reflect UV rays. Also, the closer one is to the equator, the more ultraviolet rays one is exposed to. This can be explained by the fact that the sun is usually higher at the sky at low latitudes. In addition, the ozone layer is thinner at the equator than it is over areas like the United States or Europe for example. This also contributes to more UV.
UV Rays and Sunburn
One of the most common effects of UV exposure is sunburn. Sunburn occurs when skin cells are damaged by the absorption of energy from UV rays. To compensate for this injury the skin sends extra blood to the damaged skin in an attempt to repair it thus accounting for the redness that is associated with sunburn. The amount of time it takes for a sunburn to occur is dependent mostly on the relative amounts of UV rays that are hitting the skin and on a person’s skin type. People with naturally dark skin already have inherently high levels of melanin and are thus able to spend a longer amount of time in the sun before burning. Fair-skinned people don’t have it quite so easy - burning can occur within a relatively short amount of time.
UV Rays and Aging
Another effect of ultraviolet rays on the skin is photoaging. Recent studies show that many of the symptoms commonly associated with aging (i.e. wrinkles, loosening of the skin) may instead be related to UV exposure; so though your tan may look good now, you could be paying your dues in wrinkles later.
UV Rays and Basal and Squamous Cell Carcinoma
There are three basic types of skin cancer: melanoma, basal cell carcinoma and squamous cell carcinoma. Basal and squamous cell carcinoma make up the most common and less dangerous forms called non-melanoma cancers. It is believed that ultraviolet rays (specifically UVB) are one of the chief causes in these two cancers. In order to understand why, it is helpful to know that cancers occur when mutated or damaged cells in the body begin to divide and invade other areas forcing out the healthy cells and tissues. In the case of skin cancer, the ultraviolet rays from the sun are usually the instigator. Researchers whose work is specifically geared towards squamous and basal cancers have isolated the gene suspected of being mutated, namely the p53 gene. Under normal circumstances this gene works against cancerous tumors by inhibiting the division of mutated or damaged cells. If the cell cannot be repaired, the p53 gene induces the cell to destroy itself or commit cellular suicide so that its mistakes cannot be passed on to another cell during division. If the p53 gene is mutated, however, (for example through UVB rays) then it will not stop a damaged cell from committing suicide. Thus leaving it the damaged cell to divide as normal. The damaged cells then begin to replace the healthy cells and cancer is developed. These types of cancers, though common, are not usually fatal as they rarely metastasize (extend to other parts of the body).
UV Rays and Malignant Melanoma
The causes of malignant melanoma are much less defined. Some suspect that there is a relationship between UV exposure and melanoma rates, but there are varying theories.
Some scientists theorize that UVA radiation is much more effective in causing melanoma than assumed previously. If this is the case, then many sunscreens currently available offer only very little protection against melanoma as they mostly block UVB and not UVA. This would be a possible explanation for the observed trend in melanoma cases where incidences are more prevalent among the fair-skinned population who use sunscreen than among the darker skinned, or even among the fair-skinned who don’t use sunscreen. An explanation for this lies in the nature of sunscreen: it blocks the UV-B rays that cause sunburn, thus allowing those of fair skin to stay outside for longer amounts of time and still feel "safe". Instead, they are exposing themselves to greater quantities of UVA rays, which could be increasing their risk of melanoma. The danger to sunscreen could also be two-fold, not only does it persuade people to stay in the sun longer, but habitual sunscreen users tend to lack tans, which is the body’s natural protection against both UVA and UVB. This allows even more UVA to penetrate the skin. The moral to this story? Make sure your sunscreen protects against both UVA and UVB rays. To tell, look for "Broad Spectrum" on the label which means you'll get protection from UVB and UVA rays. Our suncare products are always broad spectrum.
All information for this section was taken from the National Science Foundation Polar Programs UV Monitoring Network. Visit them here at uv.biospherical.com