Elisabeth Thieden

Background Evidence on validation of surrogates applied to evaluate the personal exposure levels of solar ultraviolet radiation (UVR) in epidemiological studies is scarce. Objectives To determine and compare the validity of three approaches, including (i) ambient UVR levels, (ii) time spent outdoors, and (iii) a modelling approach integrating the aforementioned parameters, to estimate personal UVR exposure over a period of six months among indoor and outdoor workers and in different seasons (summer/winter). Methods This validation study was part of the EU ICEPURE project and was performed between July 2010 and January 2011 in a convenience sample of indoor and outdoor workers in Catalunya - Spain. We developed linear regression models to quantify the variation in the objectively measured personal UVR exposure that could be explained, separately, by the ambient UVR, time spent outdoors, and modelled UVR levels. Results Our 39 participants – mostly male and with a median age of 35 years- presented a median daily objectively measured UVR of 0.37 standard erythemal doses (SEDs). The UVR dose was statistically significantly higher in summer and for outdoor workers. The modelled personal UVR exposure and self-reported time spent outdoors could reasonably predict the variation in the objectively measured personal UVR levels (R²= (0.75, 0.79)), whereas ambient UVR was a poor predictor (R²=0.21). No notable differences were found between seasons or occupation. Conclusions Time outdoors and our modelling approach were reliable predictors and of value to be applied in epidemiological studies of the health effects of current exposure to UVR.

There is a need for more knowledge concerning the association of higher socioeconomic status (SES) with cutaneous malignant melanoma (CMM). Having a home garden is associated with a higher SES. We aimed to study the influence of having a home garden on UVR exposure behavior and risk of CMM. Register study: We collected information from Danish national registers about gender, age, type of home and CMM among persons aged 16–75 in 2002–2006. A total of 5,118 CMM cases were identified. Risk of CMM of the trunk was increased by 46% (p < 0.001, 95% confidence interval (CI): 31–63) and risk of CMM of the extremities by 34% (p < 0.001, 95% CI: 20–49) among people with home gardens. Dosimeter study: During a summer season 194 participants living in the Capital area, Denmark, equally distributed in homes with and without a garden, wore personal electronic UVR dosimeters measuring time‐stamped UVR doses continuously and filled in sun exposure diaries. While no difference was found in estimated yearly UVR dose between groups, participants with a home garden had more days exposing shoulders or upper body, and upper extremities outdoors than those without a garden (p = 0.026, age adjusted). People with a home garden are at increased risk of CMM of the trunk and extremities—body sites that seems to be exposed to a higher extent among people with home gardens. People with a higher SES are more likely to have a home garden. This may partly explain the well‐known association of higher SES with CMM incidence.

The main purpose of this study was to investigate whether people change their sun behaviour over a period of 7 years. Thus 32 volunteers, who had all participated in earlier sun exposure studies in 1999–2001, were enrolled in a follow-up study in 2006. They were selected to represent a previous low, medium and high UVR exposure. They participated for mean 121 days (range 65–157 days) wearing a personal, electronic wrist-borne UVR dosimeter and completed sun exposure diaries. No statistically significant differences were seen from year to year in the estimated annual UVR dose, mean UVR dose per day or mean percentage of ambient UVR. However, there was a person effect showing that participants maintained a high or low UVR dose lifestyle over the years. In 2006 the 32 participants received an estimated annual mean UVR dose of 221 SED and a median dose of 154 SED (range 25–1337 SED), while they received a mean for the previous participation years (1999–2001) of 236 SED (median 153 SED, range 24–980 SED). The estimated annual UVR dose for each of the previous sun years and the estimated annual dose for 2006 correlated significantly (R² = 0.51; p < 0.0001). Sun risk behaviour, expressed as days sunbathing, did not change either. The participants thus seem to have maintained their sun exposure behaviour over a 5–7-year period.

Ultraviolet-B (UV-B) radiation increases serum vitamin D level expressed as 25-hydroxyvitamin D(3) (25(OH)D), but the dose-response relationship and the importance of dose rate is unclear. Of 172 fair-skinned persons screened for 25(OH)D, 55 with insufficient baseline 25(OH)D≤50 nm (mean 31.2 nm) were selected and randomized to one of 11 groups of five participants. Each group was exposed to one of four different UV-B doses: 0.375, 0.75, 1.5 or 3.0 standard erythema dose (SED) for 1, 5, 10 or 20 min. All participants had four UV-B sessions with 2- to 3-day interval with 24% of their skin exposed. Skin pigmentation and 25(OH)D were measured before and after the irradiations. The increase in 25(OH)D after UV-B exposure (adjusted for baseline 25(OH)D) was positively correlated with the UV-B dose (P=0.001; R(2) =0.176) but not to dose rate (1-20 min). 25(OH)D increased in response to four UV-B treatments of 3 SED with 24.8 nm on average and 14.2 nm after four UV-B treatments of just 0.375 SED. In conclusion, the increase in 25(OH)D after UV-B exposure depends on the dose but not on the dose rate (1-20 min). Further, a significant increase in 25(OH)D was achieved with a very low UV-B dose.

The influence of the summer UVR exposure on serum‐25‐hydroxyvitamin D (25(OH)D) in late summer and winter was investigated in an open study on 25 healthy, adult volunteers. The UVR exposure dose in standard erythema dose (SED) was monitored continuously during a summer season with personal, electronic wristwatch UVR dosimeters and sun exposure diaries. Constitutive and facultative skin pigmentation was measured in September. 25(OH)D was measured in September and February and was in mean 82 nmol/L ± 25 (mean ± SD) in September and 56 nmol/L ± 19 (mean ± SD) in February. The received cumulative UVR dose measured during a mean of 121 days was 156 SED ± 159 (mean ± SD). The following UVR exposure parameters correlated with 25(OH)D in September and February, respectively: (1) The cumulative UVR dose (r = 0.53; P < 0.01) and (r = 0.43; P = 0.03); (2) Mean daily hours with UVR measurements monitored by the dosimeter (r = 0.64, P = 0.001) and (r = 0.53; P = 0.007); (3) Days “with sun‐exposed upper body” (r = 0.58, P = 0.003) and (r = 0.50; P = 0.01); (4) Facultative pigmentation (r = 0.47; P < 0.02) and (r = 0.7; P < 0.001); (5) Constitutive pigmentation (r = 0.06, n.s.) and (r = 0.43, P = 0.03). Neither days “sunbathing” nor days with “sunscreen applied” correlated with 25(OH)D. The fall in 25(OH)D during winter was dependent on the entry value.

Passive sun reduction strategies, such as shaded areas in schools, are recommended

We wanted to investigate whether the use of sunbeds with sunlamps emitting mainly UVA and only 0.5% or 1.4% UVB will increase the level of serum 25‐hydroxyvitamin D (25(OH)D). In a randomized, controlled, open study on healthy, Caucasian females (>50 years) sunbed radiation was given as follows: four 6‐min sunbed sessions (days 0, 2, 4 and 7) and four 12‐min sunbed sessions (days 9, 11, 14 and 16 ) with sunlamps emitting 0.5% UVB (n = 20) or with sunlamps emitting 1.4% UVB (n = 15). The controls (n = 21) had no intervention. Serum levels of 25(OH)D were measured on days 0, 9 and 18 in all three groups. The average increase in serum 25(OH)D from day 0 to day 9 was 12 nmol L⁻¹ (SD 11 nmol L⁻¹, P = 0.0002) in the 0.5% UVB group and 27 nmol L⁻¹ (SD 9 nmol L⁻¹, P < 0.0001) in the 1.4% UVB group. From day 9 to day 18 a further but not significant increase in serum 25(OH)D of 3 nmol L⁻¹ (SD 9 nmol L⁻¹, P = 0.2) in the 0.5% UVB group and 0.6 nmol L⁻¹ (SD 18 nmol L⁻¹, P = 0.9) in the 1.4% UVB group was seen. No significant changes were found in the control group. Increasing with UVB dose and exposure time, 37–64% of the sunbed sessions resulted in side effects such as erythema or polymorphic light eruption. The results showed that sunbeds emitting 0.5% and 1.4% UVB increased 25(OH)D serum levels. The increases were dose dependent but reached a plateau after few sessions. Sunbed use as vitamin D source is, however, not generally recommendable due to the well‐known carcinogenicity and high frequency of acute side effects.

Skin cancer risk estimations are based on sun exposure data. However, the reliability of collected data in personal ultraviolet (UV) dosimeters studies has not previously been validated. We aimed at investigating the data reliability and subject compliance in a study of sun exposure behaviour among 407 subjects (age range, 4-68 years) during 54 943 days based on time-stamped personal UV dosimeter readings and diary records. By comparing diary records and UV dosimeter readings on a daily basis, we investigated subject compliance, total sun exposure record, reasons for non-responding along with rates of diary completing errors. Efforts to improve compliance were described. The subject compliance rate was median 93.5% (percent days where the diary was completed and the UV dosimeter was worn). The total sun exposure record rate was median 84.1% (percent of participation days with both UV dosimeter and diary records and where the UV dosimeter was worn). Children, adolescents and golfers had lower sun exposure record rates than the rest of the groups (P<0.05). No significant difference was found between males and females (P=0.15). The 17 non-responders were 10 children, three adolescents, one sun worshipper, two golfers and one gardener. Correctable diary completing mistakes were found in 3.1% of the days. Children made more completing mistakes than adults (P=0.001). The average estimated error rate was 3.3% and was higher for children (6.3%) and adolescents (3.6%) than the adult groups (2.4%). High subject compliance rate and data reliability were obtained because the investigators were service minded but persistent, offering dosimeter maintenance service within 24 h and scrutinized data for errors and mistakes.

Personal annual ultraviolet (UV) radiation data based on daily records are needed to develop protective strategies. To compare UV radiation exposure patterns in the winter half-year (October-March) and the summer half-year (April-September) for Danish indoor workers. Nineteen indoor workers (age range 17-56 years) wore personal UV dosimeters, measuring time-stamped UV doses continuously during a year. The corresponding sun exposure behaviour was recorded in diaries. Similar data were collected for 28 volunteers during sun holidays in the winter half-year. The relationship between UV dose and sun exposure behaviour was analysed. The ambient UV dose during the winter in Denmark (at 56 degrees N) was 394 standard erythema doses (SED) or 10.5% of the annual ambient UV dose. In winter compared with summer the subjects had: (i) a lower percentage of ambient UV radiation, 0.82% vs. 3.4%; (ii) a lower solar UV dose in Denmark, 3.1 SED (range 0.2-52) vs. 133 SED (range 69-363); (iii) less time outdoors per day with positive dosimeter measurements, 10 min vs. 2 h; and (iv) no exposure (0 SED) per day on 77% vs. 19% of the days. Sun holidays outside Denmark in winter gave a median 4.3 SED per day (range 0.6-7.6) and 26 SED (range 3-71) per trip. In the winter half-year indoor workers received a negligible UV dose from solar exposure in Denmark and needed no UV precautions. No UV precautions are needed from November to February during holidays to latitudes above 45 degrees N, while precautions are needed the whole year around at lower latitudes.