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

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

MATERIALS AND METHODS

Study location. Durban (30 deg S, 3 FEE; population of the greater Durban area is -3 million) is located on the east coast of South Africa within the subtropical high-pressure belt and consequently receives relatively high levels of ambient UVR (3).

Ambient erythemal UVR and climate monitoring. Ambient levels of erythemal UVR, weighed by the Diffey action spectrum for human erythema, were measured continuously and averaged over 10 min intervals by a Yankee Environmental Systems (YES) broadband UVB pyranometer. Although erythemal UVR is universally recognized as lying between 280 and 400 nm, the YES pyranometer measures UVR for the wave band 280-- 320 nm and automatically weighs this by the above-mentioned action spectrum to give erythemal UVR. Details of the principles of operation of the instrument are given in Prause et al. (6) and Duigan et al. (19). The YES UVB pyranometer has a 5%lo uncertainty of spectral irradiance measurements (19). The instrument is located on the roof of a building (approximately 28 m high) at the University of Natal. Erythemal UVR (in J-m^sup -2^) was converted to standard erythemal dose (SED) units, where I SED was taken to be equivalent to 100) J.m^sup -2^ (20; B. L. Diffey, personal communication). Earlier studies have used the minimal erythemal dose (MED) unit, where 1 MED is equivalent to 200 J.m^sup -2^ for skin type 11 (11). Meteorological parameters, including mean hourly temperature, wind speed and direction, humidity and daily totals of sunshine hours and rainfall, were obtained from South African Weather Service for the meteorological station situated at Durban International Airport. approximately 12 km from the location of the pyranometer.

Recruitment of subjects. Three groups of subjects were identified using similar age breakdowns to previous studies by Diffey et al. (11) and Moise et al. (13). The three age groups were 4-6 years, 7-9 years and 13-14 years. Subject recruitment was done on a volunteer basis. A preliminary meeting was held with the relevant educator at each school, and the requirements of the study were discussed. A second interactive meeting was held with the educator's class to inform them of the study and to ask for volunteers to participate in the study. From this list of volunteers, 30 subjects were selected on the basis of their fulfillment of criteria such as age, interest and enthusiasm, responsibility and ability to keep accurate records and to comply with the requirements of the study. The adaptation of a purposive rather than a random sampling technique was done to ensure a high rate of return in the face of limited resources and the inability to repeat the study should any problems arise. It was assumed unlikely that the nature of subject selection would alter behavior because the subjects were governed by formal school activities. at least during the week. Consent forms were signed by each subject's parent or guardian, and ethics approval for the study was obtained from the Nelson Mandela School of Medicine, University of Natal, Durban, South Africa.