Estimativas da distribuição de radiação solar ultravioleta recebida em diferentes partes do corpo

Abstract

Ultraviolet Radiation (UVR) is responsible for several physical, chemical and biological processes, both on the surface and in the Earth's atmosphere. In humans, UVR can cause benefits, such as vitamin D synthesis, and harm, such as burns, premature aging and skin cancer. In general, instruments and radiative transfer models are used to measure or estimate the incidence of UVR, but they take into account that the radiation is reaching a horizontal surface. For this reason, they do not reliably represent the accumulated dose of UVR in different parts of the human body, called erythemic dose (D-UVE). After all, the parts of our body are inclined in relation to the Sun, making it necessary to represent the incident UVR through a three-dimensional geometric model (MGe). Therefore, this study has the general objective of analyzing the variation in the incidence of UVR in different parts of the body considering different geographic and atmospheric characteristics, the time of exposure and the individual's position in relation to the Sun. For this, an experiment was installed, under a completely randomized experimental design, aiming to evaluate the D-UVE incident on the different parts of the body of a mannequin. The results indicated a significant interaction (p ≤ 0.05) between the D-UVE, the orientation on the dummy and the positions of the sensors on the human body. Even in the winter months, when the availability of solar radiation is lower, D-UVE can be enough to cause erythema even in less sensitive skin, regardless of the individual's orientation. In parallel, a MGe, developed in Python, was adapted to estimate the UVR on inclined surfaces, taking into account input conditions adapted to geographic and temporal variations of any location on the planet. In the first hours of the day, the D-UVE was more intense in the east orientation, in which the Sun is rising and positioning itself in relation to the horizon. Considering an hour of exposure around noon, the values observed with the face facing south are significantly higher than those observed in relation to the north, considering the position of the Sun at this time. Also, radiation fluxes on inclined surfaces at the angle of inclination of the surface relative to the horizontal plane at β = 30° are higher than on vertical surfaces, since, at β = 90°, the direct component tends to zero, therefore, prevailing only the diffuse component. As for the full-day exposure, it was observed that, even in winter, there are risks of damage to health for individuals of all phototypes. From this research, it will be possible to simulate D-UVE values on inclined surfaces for locations anywhere on the planet, with emphasis on South Hemisphere, which had not yet been the subject of research in works under these conditions. For future works, it is suggested to improve the entire methodology of the Adapted Geometric Model (MGeA), in order to analyze and compile the semi-empirical equations and specific treatments, to avoid generalist results.