ULTRAVIOLET RADIATION AND SKIN CANCER
Skin cancer is the most common malignancy in humans and accounts for one third of newly diagnosed cancers. It is estimated that skin cancer will be diagnosed in around 1 in 5 Americans during their lifetime and more than 1 million cases are diagnosed each year [1]. Ultraviolet light from the Sun is the main cause of skin cancer and plays a major role in the 2-3 million non-melanoma skin cancers and 132,000 malignant melanomas that occur annually. The incidences of skin cancer are becoming more and more common, causing global concern. There could be many reasons for this. For example, people are living longer and so their lifetime sun exposure is increased. They also have more money to spend on outdoor activities and holidays in sunny climates. Many still feel that suntans are healthy and attractive and therefore deliberately expose themselves to the sun and consequently to UV radiation [2].
Due to the causal link between UV light and skin cancer, its prevention and protection against this type of radiation has been at the forefront of a lot of research done by companies such as the World Health Organisation. They have set up a scheme called INTERSUN, a 'global UV project'. This project promotes research activities that aim to fill in gaps in knowledge and quantifies the health risks of UV exposure [3]. Everyone is exposed to UV radiation from the Sun but this exposure has only started to be considered a major concern relatively recently. This is largely due to changing environmental factors that influence the UV level at Earth. One of these factors is the Ozone layer depletion. Emission of ultraviolet radiation from the Sun covers the wavelength range 100-400 nm and is divided into three bands, UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm). As sunlight passes through the atmosphere, all UVC and 90% of UVB radiation are absorbed by ozone as well as water vapour, oxygen and carbon dioxide. UVA radiation is less affected by the atmosphere so the UV radiation that reaches the Earth's surface is mainly composed of UVA with a small UVB component [4]. As the ozone layer gets thinner, the protective filter provided by the atmosphere is progressively reduced. It is thought that for every 1% reduction in the ozone layer, there is a 2% increase in UV radiation intensity (in fact, detailed measurements of UV are one method by which scientists keep track of the total amount of ozone contained in the atmosphere). As a result, human beings are exposed to higher UV levels, more specifically, higher UVB levels which have the greatest effect on human health. The decrease in ozone levels are going to continue for a long time and the resulting increase in UV radiation reaching the Earth's surface is likely to cause serious health effects worldwide.
The risks of excessive amounts of sunlight are evident and this is one of the reasons that sunbathing is now on the decline [5]. However it is also clear that most of us are not prepared to stay out of the Sun completely therefore many prevention techniques are promoted in the hope of providing as much protection from the Sun as possible. These prevention techniques are most relevant to children as they are the ones amongst us who are least aware of UV light and its dangers. Children are at a high risk of developing skin cancer later in life because they spend much of their time outdoors in the spring and summer months, when the Sun's rays are most potent. It is believed that around 80% of our sun exposure will take place before we are 20 [6]. Many actions that we are able to take in order to protect ourselves from the most damaging solar radiation can be classified under the term 'behavioural protection'. For example, it is recommended that we stay inside or seek shade during the peak hours of solar radiation, from 10 a.m. to 2 p.m. and tightly woven clothing also helps block harmful solar radiation from reaching the skin. Using a hat or sun visor to protect your head and neck is also suggested [7]. The most extensively utilised and recommended form of behavioural protection is the application of sunscreen. As mentioned before, the UV rays that we are exposed to here on the Earth's surface consist of UVA and UVB photons. The longer wavelength UVA rays penetrate the deeper layers of the skin while the shorter wavelength UVB rays don't penetrate deeply into the skin but cause significant damage to DNA and are the primary cause of sunburn and skin cancer. It is for this reason that most of the development work in sunscreen products has been concentrated on protection from the UVB wavelengths [5]. A sunscreen acts like a very thin bulletproof vest, stopping the UV photons before they can reach the skin and inflict damage.
Skin cancer is the most common malignancy in humans and accounts for one third of newly diagnosed cancers. It is estimated that skin cancer will be diagnosed in around 1 in 5 Americans during their lifetime and more than 1 million cases are diagnosed each year [1]. Ultraviolet light from the Sun is the main cause of skin cancer and plays a major role in the 2-3 million non-melanoma skin cancers and 132,000 malignant melanomas that occur annually. The incidences of skin cancer are becoming more and more common, causing global concern. There could be many reasons for this. For example, people are living longer and so their lifetime sun exposure is increased. They also have more money to spend on outdoor activities and holidays in sunny climates. Many still feel that suntans are healthy and attractive and therefore deliberately expose themselves to the sun and consequently to UV radiation [2].
Due to the causal link between UV light and skin cancer, its prevention and protection against this type of radiation has been at the forefront of a lot of research done by companies such as the World Health Organisation. They have set up a scheme called INTERSUN, a 'global UV project'. This project promotes research activities that aim to fill in gaps in knowledge and quantifies the health risks of UV exposure [3]. Everyone is exposed to UV radiation from the Sun but this exposure has only started to be considered a major concern relatively recently. This is largely due to changing environmental factors that influence the UV level at Earth. One of these factors is the Ozone layer depletion. Emission of ultraviolet radiation from the Sun covers the wavelength range 100-400 nm and is divided into three bands, UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm). As sunlight passes through the atmosphere, all UVC and 90% of UVB radiation are absorbed by ozone as well as water vapour, oxygen and carbon dioxide. UVA radiation is less affected by the atmosphere so the UV radiation that reaches the Earth's surface is mainly composed of UVA with a small UVB component [4]. As the ozone layer gets thinner, the protective filter provided by the atmosphere is progressively reduced. It is thought that for every 1% reduction in the ozone layer, there is a 2% increase in UV radiation intensity (in fact, detailed measurements of UV are one method by which scientists keep track of the total amount of ozone contained in the atmosphere). As a result, human beings are exposed to higher UV levels, more specifically, higher UVB levels which have the greatest effect on human health. The decrease in ozone levels are going to continue for a long time and the resulting increase in UV radiation reaching the Earth's surface is likely to cause serious health effects worldwide.
The risks of excessive amounts of sunlight are evident and this is one of the reasons that sunbathing is now on the decline [5]. However it is also clear that most of us are not prepared to stay out of the Sun completely therefore many prevention techniques are promoted in the hope of providing as much protection from the Sun as possible. These prevention techniques are most relevant to children as they are the ones amongst us who are least aware of UV light and its dangers. Children are at a high risk of developing skin cancer later in life because they spend much of their time outdoors in the spring and summer months, when the Sun's rays are most potent. It is believed that around 80% of our sun exposure will take place before we are 20 [6]. Many actions that we are able to take in order to protect ourselves from the most damaging solar radiation can be classified under the term 'behavioural protection'. For example, it is recommended that we stay inside or seek shade during the peak hours of solar radiation, from 10 a.m. to 2 p.m. and tightly woven clothing also helps block harmful solar radiation from reaching the skin. Using a hat or sun visor to protect your head and neck is also suggested [7]. The most extensively utilised and recommended form of behavioural protection is the application of sunscreen. As mentioned before, the UV rays that we are exposed to here on the Earth's surface consist of UVA and UVB photons. The longer wavelength UVA rays penetrate the deeper layers of the skin while the shorter wavelength UVB rays don't penetrate deeply into the skin but cause significant damage to DNA and are the primary cause of sunburn and skin cancer. It is for this reason that most of the development work in sunscreen products has been concentrated on protection from the UVB wavelengths [5]. A sunscreen acts like a very thin bulletproof vest, stopping the UV photons before they can reach the skin and inflict damage.
