Ultraviolet radiation exposure of children and adolescents in Durban, South Africa

Photochemistry and Photobiology, Mar 2003 by Guy, Caradee, Diab, Roseanne, Martincigh, Bice

PSF as a UVR dosimeter. Davis et at. (21) first identified PSF as a reliable means of measuring individual UVR doses in 1976. It has since been widely used in many studies, including Diffey et al. (11), Holman et al. (22), Herlihy et al. (23) and Gies et al. (12.24). The PSF used in this study was 50 (mu)m thick, with a spectral sensitivity between 280 and 330 nm. The absorbance of PSF changes on exposure to UVR, and by measuring this change in absorbance at 330 nm (DeltaA^sup 330^), the degree of degradation may be quantified in terms of an erythemal UVR dose (J.m^sup -2^) through the application of a calibration equation. The calibration equation was derived through simultaneous measurements of ambient erythemal UVR using the YES UVB pyranometer, and erythemal UVR dose measured by the PSF. The postexposure absorbance measurements of the PSF strips used in the calibration procedure were undertaken 24 h after exposure. This was to allow for the darkness reaction to be completed (21) and for the PSF UVR dose to be a true representation of the UVR dose received. The calibration curve used in this study is presented in Fig. 1. It is clear from the scatter of individual points that the estimates of the erythemal UVR dose involve a measure of uncertainty, which is quantified by the 95% confidence limits. Pre- and postexposure absorbance measurements of the PSF were undertaken using a Varian DMS 300 UVR-visible spectrophotometer. Polysulfone film badges (PSFB) consisting of a strip of PSF placed in a cardboard mount with a medium-sized safety pin attached to one side of the mount were assembled. The central aperture was 1.2 x 1.6 cm. Each PSFB was numbered sequentially, the pre-exposure absorbance measure-- ment at 330 nm recorded and the badges stored in a correspondingly numbered envelope that was impervious to UVR. One PSFB was worn per subject per day for 7 days between 26 February and 4 March 2001. The PSFB was attached to the left lapel site, i.e. clavicle or collarbone, in accordance with similar studies conducted by Diffey et al. (I 1 B. L. Diffey, personal communication) and Holman et al. (22). Subjects were instructed to ensure that the PSFB were never covered by clothing, were only removed during swimming activities and were replaced in their original envelopes at the end of each day. The postexposure absorbance measurements were done on 6 March 2001 once all the PSFB were returned to ensure that they were all retained in the dark for a minimum period of 24 h. A total of 202 PSFB were returned (96% return rate), of which 192 were used in the analysis, the remaining being damaged.

The UVR exposure journal. Each subject received a resource kit containing seven PSFB, an information sheet and a UVR exposure journal. The journal provided a general introduction to the study, an indication of the roles of the subject, educator and parent or guardian in the study, guidelines on wearing the PSFB, their handling sensitivities and instructions on how to record information in the journal. The journal was completed on a daily basis for seven consecutive days. Subjects between the ages of 4 and 9 years were required to work with an adult to complete the journal. The information collected in this manner provided a continuous record of the subject's activities throughout the day, including the timing and duration of each activity, whether it took place indoors or outdoors, and if the latter, whether in the shade or sun, in addition to the type of clothing worn and whether sunscreen was applied. It was assumed that the journal entries were a true representation of the subject's activities, although it is recognized that there was individual variability in the accuracy of record keeping.