Academic journal article Central European Journal of Public Health

Climatic Factors and Epidemiologic Characteristics of Head and Neck Skin Malignancies in Osijek Baranja County, Croatia

Academic journal article Central European Journal of Public Health

Climatic Factors and Epidemiologic Characteristics of Head and Neck Skin Malignancies in Osijek Baranja County, Croatia

Article excerpt

INTRODUCTION

Climatic Factors and Carcinogenic Effects of Ultraviolet Radiation

In the last hundred years the greatest warming of the Earth's surface over the last 1,300 years has been observed. Thus, between 1906 and 2006, the average temperature rose by 0.6-0.9°C, and the rate of temperature increase has nearly doubled in the past 50 years. Long and short term changes in the intensity of solar heat radiation have had an impact on climate change (1). Thinning of the ozone layer, called the ozone "hole" is primarily a result of human activities in industry and transport. It is calculated that a 1% reduction in ozone increases UV radiation by 2% (2). Differ- ent molecules absorb greenhouse gases or different wavelengths of sunlight. For example, molecules of oxygen O2 and ozone O3 absorb almost all the sun's rays shorter than 320 nm in the ultraviolet part of the spectrum (UVB and UVC). In the spectrum of solar radiation, ultraviolet radiation accounts for only 10% of energy. The intensity of ultraviolet radiation and its composition depends on many factors including the length of the route through the atmosphere, which depends on the season, time of a day, latitude, altitude, cloudiness, and air purity (3).

The danger of UV radiation varies throughout the year. The most important influence on the intensity of sunlight at the Earth's surface is the height of the sun (season), altitude, clouds, reflections on the ground, and atmospheric ozone. UVB ultraviolet radiation level depends on the angle of solar light: it is lower in the winter, in the morning and late afternoon, and higher during the summer and at noon. Based on a series of measurements, weather reduces UV radiation in the following percentages: a clear sky allows 100% of UV radiation to pass through; high, thin clouds 89%; broken clouds 73%; and heavy clouds allow 31% of UV radiation to pass through (4). Thus, UV radiation is stronger when the sky is cloudless. Most natural surfaces, grass, soil and water reflect less than 10% of the radiation while snow can reflect up to 80% of the radiation. UV rays penetrate into the water and at a depth of ½ meter the level of radiation from the surface is 40%. When considering its effect on human health and the environment, ultraviolet radiation is usually classified into UVA (400-315 nm) or longwave (black light), UVB (315-280 nm) or medium and UVC (< 280 nm) or short (antimicrobial). Ultraviolet photons damage DNA molecules in a living organism in various ways. According to current knowledge, UVB radiation has the most powerful carcinogenic effect. Nucleic acids and proteins absorb the light of UVB region with the highest impact at 260 and 280 nm. The absorption causes damage to the cellular DNA, which, if not repaired by a particular repair mechanism, can cause mutations that may result in malignant skin tumours (5). The skin has the ability to protect itself from the negative effects of UV radiation with specific protective mechanisms. These are pigmentation, thickening of the cornual layer of the skin, DNA repair mechanisms, and activation of the body's own antioxidants. If the skin is exposed to sunlight for too long, the skin photoprotection is insufficient and the DNA repair mechanisms become overloaded (6, 7). The possible harmful effects of solar radiation on the human skin should be taken into account when it comes to the types of ultraviolet radiation UVA and UVB. UVA and UVB rays penetrate through the outer layer of the skin and cause damage, e.g., burns, skin cancer, allergies etc. So UVB ultraviolet radiation, which does not penetrate into the deeper layers of the skin, causes acute damage to the skin (erythema) in the form of burns, which leads to the degeneration of the skin, aging and can cause skin cancer (8). The harmful effects of UV rays can be acute and chronic. Acute effects are sunburn, phototoxic and photoallergic reactions (various deodorants, perfumes). Acute idiopathic actions and actinic prurigo may also occur. …

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