Bedane C. Roelandts R. Ann Dermatol Venereol ; 4SS OMS, Ginebra, Suiza, 34 pp. Gac Med Mex ; Marguery MC.
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Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8, km long.
Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage.
Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations. Thus the Brazilian Society of Dermatology has developed the Brazilian Consensus on Photoprotection, the first official document on photoprotection developed in Brazil for Brazilians, with recommendations on matters involving photoprotection.
Electromagnetic radiations are classified according to the length or frequency of wave propagation. For example, radio waves, microwaves, infrared, visible light, ultraviolet, X rays and gamma rays are names of radiation bands, ordered from the longer to the shorter wavelength.
They can also be ordered from the smaller to the larger frequency, since wavelength and frequency are inversely proportional.
Infrared, visible light and ultraviolet radiations comprise almost the total radiation emanating from the sun. Generally, the solar radiation reaching the top of terrestrial atmosphere is basically composed of:. UVR is accountable for a series of important photochemical and photobiological reactions;. Compared to other wavelengths, visible radiation undergoes less attenuation when going through the atmosphere of the Earth;.
Infrared radiation is strongly absorbed by water vapor and carbon gas present in significant amounts in the atmosphere, being therefore intimately connected with climate changes in the planet. It is important to note that these percentages concerning quantities of each radiation band show small variations related to cycles and disturbances of solar activity.
In addition, there are no precise limits for the spectral band of visible radiation, since these limits depend on the quantity of radiant energy reaching the retina and the sensitivity of the observer. The lower limit is usually between and nm, while the upper limit is between and nm. The same limits and designations of these spectral bands are also adopted by the International Organization for Standardization ISO, CIE highlights the importance of international standardization, since such bands are widely used in different medical and scientific research fields and, although some investigators use the nm limit for the division of UVA and UVB bands, the norm adopted in is still the one recommended.
This division is based on recent research that shows different types of photobiologic interaction between such bands and the DNA.
Besides the fact that it is the smallest part of solar radiation that reaches the top of the atmosphere, UVR is strongly attenuated by the terrestrial atmosphere and reaches the surface in quantities that are small, but sufficient to provide significant photobiologic effect.
UVC is completely absorbed by the oxygen and ozone present in the stratosphere, while UVB radiation undergoes strong absorption by ozone and is intensively scattered by molecules. Therefore, superficial UVR is mostly composed of UVA radiation that, while also being actively spread by the molecules present in the atmosphere, undergoes smaller ozone absorption.
In addition to these, several other environmental factors also interact with UVR, as shown below. It is important to emphasize that the superficial UVR levels depend on a group of meteorological, geographic and temporal factors.
Therefore, we cannot evaluate the influence of each of these environmental factors separately, but only as a group of elements that may depend on and influence each other. Ozone, the main absorber of UVR, is produced for the most part in the terrestrial stratosphere of the equatorial region of the planet.
However, due to the transportation mechanisms existing in the high atmosphere, a great part of the produced ozone is transported to higher latitudes. Therefore, the equatorial region of the planet has smaller quantities of ozone than higher latitude regions and the poles. Ozone layer is the name given to the region with high concentration of this gas in the Earth's atmosphere, located at a height between 15 and 30 km.
The rest of the ozone is mostly found in regions close to the terrestrial surface. During the decade, scientists observed that the ozone layer was strongly diminished in high latitude regions, especially in the poles.
The presence of chlorine or bromine in great quantities in the atmosphere unbalances the ozone formation and destruction chain, accelerating its destruction process. With less ozone, there is less absorption of UVR and, therefore, increased presence of superficial radiation. Comparisons of ozone contents measured between and show an average decrease of 3. Adhesion of the nations to the Protocol was massive and the elimination of CFC consumption has allowed a recovery of ozone levels in the entire planet.
It is foreseen that by the middle of this century the ozone layer will be completely recovered to levels existing prior to production of CFCs. The higher the altitude of a location, the thinner is the atmosphere above it and, consequently, the larger the quantity of UVR reaching the surface. In a clear sky situation, the "higher" the Sun is in the sky, the higher the levels of UV radiation are. This means that the farther the Sun is from the horizon, the shorter the optical pathway the radiation has to cross in the atmosphere.
Under these conditions, UVR undergoes less interaction with gases and particulates and, consequently, is less attenuated. Therefore, at times close to solar noon, UVR reaches its highest daytime values. The same reasoning may be used to evaluate the variation of UVR fluxes in relation to the season of the year. In the summer, the Sun reaches higher positions in relation to the horizon than in the winter and, consequently, the UVR flux is more intense.
The differences between the seasons of the year become more relevant as the latitude becomes higher. That is, in the tropics there is little difference between the position of the Sun in the summer and in the winter, while in higher latitudes this difference is quite significant. The UVR levels in clear sky days, that is, when there are no clouds, are usually higher. However, the presence of clouds tends to attenuate UVR and diminish the quantity of surface radiation.
Nevertheless, the attenuance levels may vary considerably and the clouds do not always exert adequate protection against UVR. Deep and dark clouds, as seen in rainstorms, may almost totally attenuate UVR fluxes, but thinner and lighter clouds can attenuate them only partially.
Due to this great variability, it is not possible to provide a parameter or an UVR attenuation percentage for nebulosity. There are even particular situations when the presence of cumulus or cirrus clouds may trigger a UVR intensification phenomenon and, for a short period of time, make UVR fluxes superior to those that would be observed on a clear sky day.
Solid or liquid particles found in the atmosphere are called aerosols. Soot emitted by automobiles, motorcycles and trucks or burning biomass, suspended soil dust or even sea salt from evaporated ocean water are examples of atmospheric aerosols. These particles interact with UVR, most often reflecting the radiation to other directions.
However, some types of aerosols are also able to absorb part of the incident UVR. Thus, polluted environments or those with suspended dust may show UVR attenuation in relation to clear sky situations. Nevertheless, such decrease of UVR is observed in periods of intense pollution and aerosols should not be considered as protective agents concerning sun exposure.
The term 'albedo' is used to express the relationship between the radiation reflected by a surface and the radiation such surface receives from the Sun. Therefore, UVR is reflected in different ways, depending on the surface it incides on. This is the reason why albedo may be a determining factor in the evaluation of the quantity of radiation reaching an individual. However, it is important to emphasize that there is no upper limit. The higher the value, the greater is the potential of solar damage to skin and eyes.
The variables that influence the calculation or measurement of UVI are those introduced in the previous subchapter. That is, the total ozone content of the atmosphere is taken into account, as well as the geographic position of the location the closer it is to the Equator line, the higher the UVI ; the altitude of the surface at high altitudes, higher UVI are observed ; the time of day most of the UVR reaches the surface at times close to solar noon ; season of the year the UVI escalates in the summer and diminishes in the winter ; atmospheric conditions the UVI are generally higher in days of cloudless skies ; and type of surface.
The use of this scale is an important tool to orient the population regarding the risks of excessive solar exposure. The category designated "low UVI" usually happens at times close to dawn and sunset, in addition to moments when a great mass of dense clouds covers the sky.
However, it is always very important to be extremely careful in evaluating UVI when there are clouds, since nebulosity may not significantly attenuate UVR or even intensify radiation levels in short periods of time.
Ever since the second half of last century, studies about the UVR emitted by artificial sources have been carried out to clarify the relationship between the use of fluorescent lamps and the incidence of cutaneous melanoma. Such studies reflect the concern about the possibility of increased risk of incidence of skin cancer, melanoma and non melanoma, in individuals exposed to UVR emitted by these lamps. In , for example, Swerdlow et al.
The types of lamps found in the market are halogen quartz lamps, incandescent lamps with a tungsten filament, tube fluorescent and compact fluorescent lamps. In all of the continents, discussions regarding the rational use of energy are increasingly frequent subjects and a priority in government agendas. In this scenario, incandescent lamps with a tungsten filament are being replaced by compact fluorescent lamps due to their low energy consumption, both for domestic and commercial use.
Few papers have been published related to UVR emission by artificial lighting sources. The quantities of UVA and UVB emitted by commonly used lamps are very small and totally blocked by the protective membrane currently included in the glass casing of lamps. Thus, there are no reports about UVR emission by the lamps found on the market.
Although they do not emit UV radiation, the lamps are visible light emitting sources and present variations within the electromagnetic spectrum that may affect individuals with other skin diseases, such as melasma, for example, depending on exposure intensity and frequency. A significant set of data collected in the last few years in several regions of Brazil allows us to trace the behavior of ultraviolet solar radiation in Brazilian soil more accurately.
We will see that these data show a great need to better educate our population regarding the risks of solar exposure without adequate protection. In Brazil, there is generous offer of ultraviolet radiation.
UVR roughly presents higher values for smaller geographic latitudes, but other factors like altitude, season of the year, time of day and meteorologic characteristics such as presence of clouds and atmospheric pollution also influence the intensity of solar radiation. Despite these variations, UVR levels in clear sky conditions are always very high in every season of the year and in almost the entire Brazilian territory.
Taking into account geographic position, the North and Northeast regions present the highest cumulative doses of ultraviolet radiation. This means that, in those regions, UVR levels are high and vary little during the entire year. On the other hand, in the South and Southeast regions the effect of the seasons of the year is quite perceptible, so that UVR levels show great variability between winter and summer.
It is important to highlight the fact that, in the summer, the Southeast region presents record UVR intensity observed in the country, with levels even higher than in the Northeast region.
This occurs due to the geographic position of the Brazilian Southeast region. Therefore, in the summer, the sun reaches its highest point at noon and, consequently, in a clear sky day, UVR levels are more intense. The UV radiation distribution here presented considered only the geographic positions of Brazilian regions.
However, it is important to take into account also the meteorologic factors, such as the occurrence of rainy seasons, with the presence of deep clouds that significantly attenuate UV radiation. The Central region of Brazil, for example, may receive great incidence of solar radiation during the dry seasons autumn and winter , as there is less rainfall and an even larger number of clear sky days. This daytime UVR variability due to the presence or absence of clouds influences the cumulative radiation dose to which an individual is exposed.
It is a reason for concern to observe that, even in the winter, a person exposed without protection in the period between a. This is a reality for many Brazilian workers. In our country, the cultural trend of solar exposure on beaches is still very popular. Most of the tourists visit Brazilian beaches in the period of greater incidence of UVR, being subject to large UVR quantities and their related hazards.
Como seleccionar la proteccion solar
Brazil is a country of continental dimensions with a large heterogeneity of climates and massive mixing of the population. Almost the entire national territory is located between the Equator and the Tropic of Capricorn, and the Earth axial tilt to the south certainly makes Brazil one of the countries of the world with greater extent of land in proximity to the sun. The Brazilian coastline, where most of its population lives, is more than 8, km long. Due to geographic characteristics and cultural trends, Brazilians are among the peoples with the highest annual exposure to the sun. Epidemiological data show a continuing increase in the incidence of non-melanoma and melanoma skin cancers. Photoprotection can be understood as a set of measures aimed at reducing sun exposure and at preventing the development of acute and chronic actinic damage. Due to the peculiarities of Brazilian territory and culture, it would not be advisable to replicate the concepts of photoprotection from other developed countries, places with completely different climates and populations.
2014, Número 4
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