Scaling analysis of personal solar UVR exposure records

Abstract

Personal sun exposure measurements provide important information to guide the development of sun awareness and disease prevention campaigns. We have investigated scaling properties of personal solar ultraviolet radiation exposure (pUVR) records using the Wavelet Transform (WT) spectral analysis. Personal UVR recordings were collected by UVR monitors designed to measure erythemal (or sunburning) UVR and calculate daily erythemal pUVR exposures. We have analyzed sun exposure recordings of school children, farmers, marathon runners and outdoor workers in South Africa, and outdoor workers and work site supervisors in New Zealand. We found scaling behavior in all the analysed pUVR datasets. We found that the observed pUVR scaling changes from uncorrelated to long-range correlated with increasing duration of sun exposure. Peaks in the WT spectra that we found suggest the existence of characteristic times in sun exposure behavior that were to some extent universal across our dataset. Our study also showed that scaling measures enable group classification, as well as distinction between individual UVR exposures, otherwise unattainable by conventional statistical methods. In cases of continuous personal daily exposure, associated with high daily exposure indexes, the scaling analysis proved able to differentiate the high dose UVR exposure behavior from the continuous low risk outdoor behavior.