About UV Rays

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 - UVA being the longest and UVC the shortest. Why is this important? Well they differ in the amount of energy they contain, their effects on biological matter, and their ability to penetrate the skin. According to the World Health Organization (WHO)

The shorter the wavelength, the more harmful the UV radiation. However, shorter wavelength UV radiation is less able to penetrate the skin.

Luckily, UVC rays (the shortest ones) do not reach the earth’s surface because they are filtered by the atmosphere. 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 welding. Again, a quote from the WHO is enlightening

Short-wavelength UVC is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface.

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. While not all UVB reaches the earth surfaces, those that due are still responsible for skin damage liking tanning, burning, wrinkles and skin cancer.

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. In fact, according to the WHO 95% of the UV radiation reaching the earth's surface is UVA. Like UVB, UVA also causes tanning, burning, skin aging and skin cancer.

As both UVB and UVA rays can be detrimental to our health, it is important that we protect ourselves. That is why it is important to always use a "broad spectrum" sunscreen (like ours) since only broad spectrum sunscreens give you UVB and UVA protection.

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 include the position of the sun in the sky, the amount of ozone present, the cloud coverage and the type of 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. In this case, 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, latitudes closer to zero (closer to the equator) generally have higher UV levels for two reasons. One - closer to the equator the sun's rays have a shorter distance to travel through the atmosphere. Two - the ozone layer (part of the atmosphere responsible for filtering UV rays) is generally thinner at the equator.

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 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, then it will not cause a damaged cell to commit suicide, thus leaving the damaged cell to divide as normal. The damaged cells then begin to replace the healthy cells and cancer develops. 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 less defined but, according to the WHO, the Skin Cancer Foundation and the National Institutes of Health, recent research suggests UV rays can cause melonoma.

Additionally, while it is generally acknowledged that both UVB and UVA rays cause skin cancer, there is some thought that UVA radiation is more effective in causing melanoma than assumed previously. That is why it is important to use a broad spectrum sunscreen (check the label for the phrase). A broad spectrum sunscreen means the product has undergone testing to prove it protects against both UVB and UVA rays. Our SPF products are all broad spectrum.

Information for this section was taken from the National Science Foundation Polar Programs UV Monitoring Network and the World Health Organization.

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