Sun exposure at school

Photochemistry and Photobiology, Aug 1999 by Moise, A F, Buttner, P G, Harrison, S L

Measurement times. All measurements were conducted during the last week in July, which was well within term 3 of the school year. According to the daily breaks for the students, the measurements occurred within the following four periods: Period 1, 0935-1055, special sport activity, every Wednesday; Period 2. 1055-1140, morning lunch break, every day; Period 3, 1300-1345, main lunch break, every day: and Period 4, 1345-1505, special sport activity, every Friday. There was at least one set of measurements taken at each location for each period and for each day during the whole study.

Measurement procedure. A set of measurements was obtained through measuring both, under the shaded setting and outside the shaded setting (nearby). Also, each measurement was done pointing the sensors first toward the zenith (in future called vertical measurement) and then toward the horizon (in future called horizontal measurement). Readings were taken not instantaneously, but in integral mode over a 5 min interval. This ensured that the UVB dose could be determined even in low-level UVB settings such as under dense foliage.

Correlation with er themal dose. In order to estimate the erythemally effective dose (EED) reaching each shade setting, UVB measurements were compared to measurements from a routinely operating UV-Biometer at James Cook University, Douglas campus. This instrument measures directly the EED in units of MED/h with I MED (minimal erythemal dose) equal to 200 J/m2 of erythemally weighted solar UVR that could be seen as the amount of effective UVR necessary to produce barely perceptible redness of the skin in people with skin type I (most sun sensitive) (19). Only recently, the CIE (Commission Internationale d'Elairage) (20) introduced a standard erythemal dose (SED) in order to have a skin-type-independent measure of the erythemal dose with 1 SED being 1001/m2 of EED (21).

Questionnaire. In addition, a random sample of 70 grade 8 students (41 boys, 29 girls) were interviewed about their sun-exposure habits at school. The short standardized interview collected data on personal characteristics of the students such as hair color and freckles, on knowledge about sun and skin cancer and on their individual behavior at school. In particular, the students were asked to mark on a map of the school yard where they usually spend their time during school breaks. These data were finally coded as indoor, under tree and shadecloth, under tree, near building and no shade, reflecting the places UV measurements had been taken previously.

DISCUSSION

The main findings of this study can be summarized in two points: (1) the level of erythemally effective radiation received by school children during their routine breaks was high. Unprotected body sites such as arms, face and legs could have been exposed to a daily dose as high as 12.8 SED on average if they would have spent their break period not under shaded settings. Even when sitting or standing under a verandah roof next to the school buildings, this average daily dose was still 3 SED. The questionnaire from the grade 8 students suggested that it was the sport activities and not the lunch breaks when they received most of their UV radiation dose. Not included in our study were outdoor activities that do not occur on a weekly basis, such as the sports carnival and swimming activities. (2) Most of the students from grade 8 did not use sun-protective means.