Literature Review (Brief summary of at least 3 sources that you have consulted with reference to your research topic)
We used the following links to assist us in our research study.
- "Effects of UV Radiation on You." Student's Guide-. Biospherical.com, n.d. Web. 07 Feb. 2014 <http://uv.biospherical.com/student/page4.html>.
There are positive effects of UV rays on us. For an instance, they assist our body in the production of Vitamin D that helps strengthen bones in our body and protect us from diseases from bacteria such as Rickets. They also reduce the risks of having certain cancer (e.g. colon cancer) Moreover, it aids in the treatment of psoriasis, a condition whereby the skin shed its cells too quickly, which results in itchy scaly patches of skin. During the treatment, UV rays are shone onto the infected area, as they are exposed to the rays, the growth of the cells are slowed down, thus relieving the condition.
However, we have to bear in mind that there are not only positive effects that UV rays bring about to us. It can also cause harmful effects which can lead to increased health problems.
Of the many common effects that are brought about due to overexposure of UV rays, sunburning or erythema occurs. Another effect is photoaging, many common symptoms are wrinkles and loosening of skin.
In order to inform the public about the intensity of UV radiation the UV index was invented and is now published in newspapers and on TV. If the Index reads 1-3 this means there is low exposure; whilst 4-6 means medium; and 7-9 means high. The UV index is directly proportionate to the UV exposure levels.
Ultraviolet rays can be reflected towards the eyes by certain substances, such as sand and snow. Due to this, the amount of UV rays the eyes are exposed to is increased. Which then leads to the condition, photokeratitis, also known as snow blindness. Photokeratitis is a sunburn of the cornea, and usually recedes within one to two days. It occurs when the eyes are exposed to large quantities of UV light in a short amount of time. The reflection of UV rays off of snow and sand are enough to incur this injury.
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. UV rays, especially UV-B rays are one of the main causes of this diseases.
Some scientists hypothesised that UV-Radiation is much more effective in causing melanoma than assumed previously.
- “World Health Organization- Health effects of UV Radiation” <http://www.who.int/uv/health/en/>
Small amounts of UV are beneficial for people and essential in the production of vitamin D. UV radiation is also used to treat several diseases, including rickets, psoriasis, eczema and jaundice.
Prolonged human exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye and immune system. Sunburn (erythema) is the best-known acute effect of excessive UV radiation exposure. In the long run, UV radiation induces degenerative changes in cells of the skin, fibrous tissue and blood vessels leading to premature skin aging, photodermatoses and actinic keratoses. another effect is an inflammatory reaction of the eye. In the most serious cases, skin cancer and cataracts can occur.
Worldwide some 12 to 15 million people become blind from cataracts annually, Furthermore, a growing body of evidence suggests that environmental levels of UV radiation may suppress cell-mediated immunity and thereby enhance the risk of infectious diseases and limit the efficacy of vaccinations.
Using established methodology and best available estimates on UV-related mortality and morbidity, this report estimates that annually around 1.5 mill DALYs (Disability-adjusted life years) are lost through excessive UV exposure. A counterfactual zero population exposure to UV would generate a substantial burden of disease through diseases of vitamin D deficiency. This, however, is only a theoretical possibility since the large majority of people is casually exposed to UV radiation such that extremely low Vitamin D levels are rarely found.
3. "Positive and Negative Effects of UV." Science Learning Hub RSS. N.p., n.d. Web. 10 Feb. 2014. <http://www.sciencelearn.org.nz/Contexts/You-Me-and-UV/Science-Ideas-and-Concepts/Positive-and-negative-effects-of-UV>.
Over-exposure to UV radiation has a harmful suppressing effect on the immune system. Scientists believe that sunburn can change the distribution and function of disease-fighting white blood cells in humans for up to 24 hours after exposure to the sun. Repeated over-exposure to UV radiation can cause even more damage to the body's immune system. The immune system defends the body against bacteria, microbes, viruses, toxins and parasites(disease and infection). You can see how effective the immune system is by looking at how quickly something decays when it dies and the immune system stops working.
4.1 Key findings
From the data collected and obtained from various sources online, we can conclude that UV ray index does affect the rate of skin cancer. For example, for the data on Australia, from the years 2000 to 2002, the UV ray index increased from 11.3 to 11.6, and then finally to 12.3. For the same years, the cancer rates increased as well, starting from 5.3 to 5.5, and then reaching 5.7. Similarly, for the data on US, the UV ray index decreased from 9 to 8.5 in the years 2002 and 2003. The skin cancer rates for those years decreased too. The incidence rate per 100,000 people decreased from 2 to 1.8. Thus, we can conclude that the UV ray index and the skin cancer rates are dependent on each other.
4.2 Explanation of key findings
When the UV ray index increases, the UVA and UVB rays inevitably increase. UVA rays are largely responsible for the cause of skin cancer as it penetrates our skin more deeply compared to UVB. The examples in 4.1 clearly show that when the UV ray index increases, there would be an increase in the skin cancer rate.
4.3 Evaluation of hypothesis
Proposed hypothesis: The UV ray index and the skin cancer rates are related. When the UV ray index increases, skin cancer rates increase as well.
Our hypothesis is proven to be correct. Our data shows that when the UV ray index increases, the skin cancer rates also increased, vice versa. This hypothesis is similar to a research European Journal of Cancer (2005).
4.4 Areas for improvement
There are a few things that we can improve on.
Firstly, we could have gotten more data of more cities and countries. Most of the data on the Internet did not adhere to our needs of getting data for UK and Asia. We could only get the data for Australia and America.
Moving on, it would have helped if we had a larger range of years for the UV ray data as well as the cancer rates. This would have helped us a lot in getting more accurate results and more reliable analysis being made.
Next, there were many variables to be considered in this research, for example the different states of that particular country. It was difficult to find data that matched up as different countries had data for different years, therefore this took us a long time to find a range of years that matched up to the data we had collected so far.
Last but not least, we would have also liked to have average of the UV ray index during all the seasons, from winter to summer. It would have been easier if the countries that we were researching on had provided the average UV ray index already as we had to add up all the data we had collected and divide it to make sure we had a correct average. This took up a lot of time and it was tedious as well.
It would also have helped us if the results were more specific because we had a lot of data and it took a lot of time for us to sort through everything. However, we also have to consider the different variables that might have affected our results, like age group, gender or those who go for tanning.