Concurrent evaluation of personal damaging and beneficial UV exposures over an extended period

Personal exposure to solar ultraviolet radiation (UVR) is acknowledged as having both positive and negative effects on human health. This study aimed to measure concurrently the personal erythemal UV, UVA and vitamin D effective exposures of participants in each season of a year. Participants were all indoor office workers located at two different sites less than 6.5 km apart at the sub-tropical location of Toowoomba (27°33'S 151°55'E). The subjects wore a combined dosimeter badge horizontally on the shoulder for a minimum of one week in each season; this badge used 8-methoxypsoralen film to record the UVA waveband and polyphenylene oxide film for the erythemal and the vitamin D effective UV wavebands. The results show that median erythemal exposure was highest during the spring and lowest during winter, as was the vitamin D effective exposure. Median UVA exposures were at a similar level in winter and summer, autumn was higher (double) and spring at a lower level. The duration and time of day participants spent outdoors changed in each season; in winter, participants spent an average of 101 minutes outdoors between 10:00-14:00 h over the week, whereas in summer this fell to 79 minutes even though they were outdoors more often. The daily UVA/UVB ratio is lowest between 10:00-14:00 h and also changes with the season resulting in the differences between the distributions of exposure for each of the wavebands. Each category of exposures must be assessed individually as each season and each waveband has different distributions. The results also demonstrate that the dual film dosimeter developed and characterized with a calibration to three different biological responses, is an effective device for the concurrent measurement of erythemal UV, UVA and vitamin D effective UV exposures for periods of up to seven days.