Obstrução do céu e radiação UV : critérios para a geração de espaços urbanos saudáveis

Abstract

Ultraviolet radiation plays a key role in human health, with beneficial effects such as vitamin D synthesis from moderate exposure and detrimental effects such as erythema and skin cancer caused by excessive exposure. In the face of the lack of a global consensus, the adoption of new urban planning regulatory frameworks is needed, especially those that promote solar access. Rapid urbanization represents a challenge for the creation and maintenance of urban spaces with solar access, especially due to obstructions that reduce the availability of the sky. Depending on the degree of obstruction, urban shadows can be considered an alternative to improve the quality of these spaces. Thus, this research investigated the interaction between sky obstructions and solar ultraviolet (UV) radiation, establishing criteria for the generation of healthy urban spaces in low-latitude regions. The experimental studies highlighted surveys and measurements of UV Index (UVI) and UV radiation in urban areas located in the city of Joao Pessoa/PB. The measuring stations were composed of two open and unobstructed areas (Sun Station) and six areas shaded by trees and buildings (Shade Station). Three indicators of urban morphology were applied to evaluate the sky obstructions: Sky View Factor, Sun Coverage Factor, and Segmented Sky Factor. For the UV radiation measurements, the low-cost solution was adopted, with the intercomparison between instruments, using the Sensu Comfort Meter and the Ground Ultraviolet Radiometer - GUV. Polynomial models were satisfactory, with good adequacy of the residuals, especially among the UVIs. Results indicated that the UVI reached maximum values of extreme risk above 11, with margins prone to deleterious effects. There was a greater hourly association of UVI with global radiation than time ranges. Sky fraction above 0.40 recorded high levels of UV radiation with a higher probability of D synthesis before 10 a.m., while those below 0.10 showed greater attenuation to UV rays to the point of not contributing to the increase in vitamin D status. Under clear skies, close to solar noon. The research highlighted the importance of the morphological characteristics of urban spaces in the regulation of exposure to UV radiation, highlighting the potential benefits of shaded green areas for the synthesis of vitamin D. This suggests the implementation ofpublic urban planning policies for the creation of quality green spaces and the construction of more resilient and healthy community.