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

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

Ultraviolet Radiation Exposure of Children and Adolescents in Durban, South Africa

ABSTRACT

The solar ultraviolet radiation (UVR) exposure of 30 children and adolescents in three age groups (4-6 years, 7-9 years and 13-14 years) was measured for 1 week in late summer (February-March) in Durban, South Africa, using UVR-- sensitive polysulfone film badges (PSFB) attached to the lapel region of the body. The mean and median values for all ages over the study period were 2.0 and 1.2 standard erythemal dose (SEP) units, respectively, where 1 SED = 100 J-m^sup -2z^. Individual PSFB doses were analyzed as a function of age, gender and behavior. No significant statistical differences were found between different age groups; however, there was a statistical difference between males and females, with males generally receiving higher PSFB doses. Subjects completed UVR exposure journals documenting their time outdoors, shade versus sun conditions, nature of their activities, clothing worn and their use of sunscreen for each day of the study. Activity patterns were noted as the most important factor influencing individual UVR dose. Ambient erythemal UVR was measured by a Yankee Environmental Systems UVB pyranometer, and a relationship between ambient UVR and individual UVR dose was derived. On average, subjects received a dose of 4.6% of the total daily erythemal UVR. Based on this factor, the potential dose of an individual over a full annual cycle was estimated. Accordingly, there were 139 days during the year when an individual with skin type I (light skin) would be likely to experience minimal erythema and 97 and 32 days for individuals with skin types II and III, respectively.

Abbreviations: MED, minimal erythemal dose; MMSC, malignant melanoma skin cancer; PSF, polysulfone film; PSFB, polysulfone film badge; SED, standard erythemal dose; UVR, ultraviolet radiation; YES, Yankee Environmental Systems.

INTRODUCTION

Stratospheric ozone plays an important role in absorbing solar ultraviolet radiation (UVR) and hence in reducing the amount of UVR received at the earth's surface. Depletion of the ozone layer has raised concern about an expected increase in surface UVR levels. Although downward trends in total column ozone are widely documented, including South Africa (1-3), corresponding upward trends in surface UVR are not as readily detectable because the UV band comprises a relatively small portion of the electromagnetic spectrum (UVA [320-400 nm] == 6.3%; UVB [280-- 320 nm] == 1.5%) (4). However, a number of studies have noted an inverse relationship between total column ozone and surface UVR, including Herman et al. (5), Bodeker and Scourfield (3) and Prause et al. (6).

Overexposure to relatively high levels of surface UVR is known to have adverse effects on biological systems. The effects of increased UVR on human health include photoaging of the skin, erythema, cataracts and skin cancer (7-9). There are two types of skin cancer: nonmelanoma skin cancer, including basal cell carcinoma and squamous cell carcinoma, and malignant melanoma skin cancer (MMSC).

Many studies have noted a relationship between childhood UVR exposure and the development of skin cancer, particularly MMSC, during adulthood (10-16). Overexposure to UVR before the age of 20 years is thought to increase this risk, particularly in terms of developing MMSC (13,17).

Cancer statistics indicate that, when compared with other countries, South Africa has one of the highest skin cancer rates in the world (18). For this reason, a study investigating UVR exposure in South Africa is justifiable. Recognition that childhood exposure plays a significant role in increasing the risk of skin cancer underlines the importance of focusing on the UVR doses and exposure patterns of children and adolescents to assess the personal risk and to determine preventative methods. This study will focus on young children and adolescents residing in the city of Durban, South Africa.

Similar studies recording individual UVR doses and exposure patterns have been undertaken elsewhere. For example, Diffey et al. (11) measured the UVR doses of children aged 9-10 years and 14-15 years in three geographically distinct regions in England for a 3 month period during summer. Gies et al. (12) assessed the UVR doses of primary school children in Brisbane, Toowoomba and Mackay (Australia) for a 2 week period, and Moise et al. (14) measured the UVR exposure of infants and small children living in Townsville, Australia. However, it is believed that the investigation described in this article is the first of its kind in South Africa.

The study aims to provide a measure of the UVR exposure of preprimary, primary and high school children during the school term. Objective measurements of UVR dose were obtained using UVR-sensitive polysulfone film (PSF). The relationship between UVR dose and age, gender and behavior was also analyzed, as has been done in other studies. A unique feature of this research is the attempt to relate the individual UVR dose to the ambient UVR radiation and to discuss the annual risk of minimal erythema according to the skin type.