Sun exposure behaviour among subgroups of the Danish population. Based on personal electronic UVR dosimetry and corresponding exposure diaries.

Solar ultraviolet radiation (UVR) is known to be the most important etiological factor in skin cancer development. The main objective of this thesis was to achieve an objective, basic knowledge of the individual UVR exposure dose pattern and to reveal the factors and with which power they influence on the UVR dose among the Danes. Eight open prospective, observational studies and one study analyzing the compliance and reliability of data were performed in healthy Danish volunteers with an age range of 4-68 years. The subjects were chosen to cover an age span group of children, adolescents, and indoor workers and in addition, groups with expected high UVR exposure, sun worshippers, golfers, and gardeners. We developed a personal, electronic UVR dosimeter in a wristwatch (SunSaver). The subjects wore the UVR dosimeter that measured time-stamped UVR doses in standard erythema doses (SED) and completed diaries with data on their sun exposure behaviour. This resulted in corresponding UVR dosimeter and diary data from 346 sun-years where one sun-year is one person participating in one summer half-year (median 119 days). The annual UVR doses were calculated based on the personal and ambient measured UVR doses. We found a huge variation in annual UVR exposure dose within the total population sample, median 173 SED (range, 17-980 SED). The inter-group variation in annual UVR dose was from median 132 SED among indoor workers to median 224 SED among gardeners. No significant correlation was found between annual UVR dose and age either within the total population or among the adults. But the subjects below 20 years of age had an increase in annual UVR dose of 5 SED per year. Young people before the age of 20 years did not get a higher proportion of the lifetime UVR dose than expected (25%) when assuming a life expectancy of 80 years. There was no significant difference in annual UVR dose between males and females in the total population sample. But, among children, girls received a significantly higher UVR dose than boys due to more days with risk behaviour (sunbathing or exposing shoulders outdoors). This exposure pattern, with females having more risk behaviour than males, was also found among adolescents and adults. Sunbathing or exposing shoulders (risk behaviour) outside the beach resulted in a median of 2.5 SED per day in northern Europe and 3.2 SED per day in southern Europe, while the corresponding values were 4.6 SED and 6.9 SED per day at the beach. UVR doses above 10 SED per day were connected with risk behaviour. The subjects had a median of 13 days with risk behaviour (range, 0-93 days). The subjects used sunscreen on a median of five days (range, 0-130 days), but have a median of seven days with risk behaviour without sunscreen applied (range, 0-47 days). They had a median of one sunburn per sun-year (range 0-10). Fifty percent of the UVR dose was received between 12.00 and 15.00. Only the gardeners received the main part of their UVR dose on workdays. Conclusions : - High UVR doses are connected with risk behaviour. Reduction of cumulative lifetime UVR dose could be obtained by minimizing risk behaviour. - Sunburns were highly correlated to risk behaviour. - Use of sunscreen correlated with days "sunbathing with the intention to tan", indicating that sunscreens were used to avoid sunburn during risk behaviour. - Scheduling lunch breaks and other breaks indoors at noon, where ambient UVR peaks, could reduce the occupational UVR exposure significantly. - In the winter-half-year in Denmark. the UVR dose received from solar exposure is negligible and no UVR precautions are needed. This study documented that high subject compliance rate and data reliability could be obtained in long-time UVR dosimeter study as ours by being service minded but persistent, offering dosimeter maintenance service within 24 hours and scrutinizing data for errors and mistakes just after data collection.