Comparative Study of Healthy Older and Younger Adults Shows They Have the Same Skin Concentration of Vitamin D3 Precursor, 7-Dehydrocholesterol, and Similar Response to UVR

Vitamin D3 synthesis in human skin is initiated by solar ultraviolet radiation (UVR) exposure of precursor 7-dehydrocholesterol (7DHC), but influence of age on the early stage of vitamin D3 metabolism is uncertain. We performed a prospective standardised study in healthy ambulant adults aged ≥65 and ≤40 years examining (1) if baseline skin 7DHC concentration differs between younger and older adults and (2) the impact of older age on serum vitamin D3 response to solar simulated UVR. Eleven younger (18-40 years) and 10 older (65-89 years) adults, phototype I-III, received low-dose UVR (95% UVA, 5% UVB, 1.3 SED) to ~35% of the body surface area. Biopsies were taken for 7DHC assay from unexposed skin, skin immediately and 24 h post-UVR, and blood sampled at baseline, 24 h and 7 d post-UVR for vitamin D3 assay. Samples were analysed by HPLC-MS/MS. Baseline skin 7DHC (mean ± SD) was 0.22 ± 0.07 and 0.25 ± 0.08 µg/mg in younger versus older adults (no significant difference). Baseline serum vitamin D3 concentration was 1.5 ± 1.5 and 1.5 ± 1.7 nmol/L in younger versus older adults, respectively, and showed a significant increase in both groups post-UVR (no significant differences between age groups). Thus, skin 7DHC concentration was not a limiting factor for vitamin D3 production in older relative to younger adults. This information assists public health guidance on sun exposure/vitamin D nutrition, with particular relevance to the growing populations of healthy ambulant adults ≥65 years.

Balancing the risks and benefits of sun exposure: A revised position statement for Australian adults

OBJECTIVE

To describe the development of a new position statement regarding balancing the risks and benefits of sun exposure for Australian adults.

METHODS

We conducted a Sun Exposure Summit in March 2021, with presentations from invited experts and a workshop including representation from academic, clinical, policy, and patient stakeholder organisations. The group considered advice about balancing the risks and benefits of sun exposure for Australian adults and developed a revised consensus position statement.

RESULTS

The balance of risks and benefits of sun exposure is not the same for everybody. For people at very high risk of skin cancer, the risks of exposure likely outweigh the benefits; sun protection is essential. Conversely, people with deeply pigmented skin are at low risk of skin cancer but at high risk of vitamin D deficiency; routine sun protection is not recommended. For those at intermediate risk of skin cancer, sun protection remains a priority, but individuals may obtain sufficient sun exposure to maintain adequate vitamin D status.

CONCLUSIONS

The new position statement provides sun exposure advice that explicitly recognises the differing needs of Australia's diverse population.

IMPLICATIONS FOR PUBLIC HEALTH

Mass communication campaigns should retain the focus on skin cancer prevention. The new position statement will support the delivery of personalised advice.

100 YEARS OF VITAMIN D: Dose-response for change in 25-hydroxyvitamin D after UV exposure: outcome of a systematic review

A systematic review of publications addressing change in vitamin D status (25-hydroxyvitamin D (25OHD)) after exposure to UV radiation identified 2001 independent peer-reviewed publications. Of these, 21 used artificial sources of UV radiation, met all inclusion criteria and were quality assured; 13 publications used solar radiation and met sufficient inclusion criteria to be retained as supporting evidence; 1 further included publication used both solar and artificial sources. The review consistently identified that low dose, sub-erythemal doses are more effective for vitamin D synthesis than doses close to a minimum erythema dose; increasing skin area exposed increases the amount of vitamin D synthesised although not necessarily in a linear manner; constant dosing leads to a dose-dependent plateau in 25OHD, and dose-response is greatest at the start of a dosing regime; there is a large interpersonal variation in response to UV exposure. Fourteen of the studies using artificial sources of radiation were used to determine a dose-response relationship for change in 25OHD on whole-body exposure to repeated sub-erythemal doses of UV radiation, taking the form Δ25OHD (nmol/L) = A ln(standard vitamin D dose) + B. This helps quantify our understanding of UV as a source of vitamin D and enables exposure regimes for safe synthesis of vitamin D to be assessed. Specific studies of people with pigmented skin (Fitzpatrick skin types 5 and 6) were rare, and this dose-response relationship is only applicable to white-skinned individuals as skin type is a determinant of response to UV radiation. Findings provide information for vitamin D guidance updates.

Older Adults Who Spend More Time Outdoors in Summer and Have Higher Dietary Vitamin D Than Younger Adults Can Present at Least as High Vitamin D Status: A Pilot Study

Vitamin D₃ can be produced by exposing skin to UVB radiation or sourced through dietary products. It is often stated that vitamin D status declines in older adults, yet little is known about differences in current-day lifestyle and dietary behaviours influencing vitamin D outcomes in younger (18–40 years old) and older adults (65–89 years old). Our objectives were to perform a pilot study to compare sun exposure behaviours, i.e., time spent outdoors, holiday behaviour and use of sunscreen/clothing, and dietary vitamin D intake, in young and older adults in the UK, together with assessment of their vitamin D status. A total of 13 young and 11 older volunteers completed a four-page questionnaire to assess sun exposure and photoprotective behaviour and an eleven-page one-week vitamin D diet diary, alongside their plasma 25(OH)D measurement. It was found that the older group tended to spend more time outdoors during the working week in summer, to take more summer and winter holidays each year, take longer winter holidays and have similar sunscreen use when compared to younger adults. Older adults had a significantly higher daily dietary intake of vitamin D (4.0 μg) than young adults (2.4 μg). Mean winter 25(OH)D concentration was higher in older (56.9 nmol/L) than in young adults (43.2 nmol/L), but there was no statistical difference between the groups. Contrary to common assumptions, in this study, older adults had sun exposure and dietary behaviours conferring a vitamin D status at least as good as that of younger adults.

Photoprotection conferred by low level summer sunlight exposures against pro-inflammatory UVR insult

Tanning (melanisation and epidermal thickening) is a photoprotective response to solar UVR exposure, but it has been unclear to what degree low-level exposures induce this, or whether this modifies the histological inflammatory response to UVR.

Public Awareness and Behaviour in Great Britain in the Context of Sunlight Exposure and Vitamin D: Results from the First Large-Scale and Representative Survey

In recent years, UK public health messages about the risks of sunlight exposure (skin cancer) have been increasingly balanced by messages about its benefits (vitamin D production). Currently, data about the effects of this shift on public knowledge, awareness, and behaviour are scant. Thus, the objective of this paper is to report the findings of the first large-scale and representative survey of the awareness, knowledge, and behaviour of adults in Great Britain (England, Scotland, and Wales) (n = 2024) with respect to sunlight exposure, vitamin D, and sunburn and skin cancer. The findings suggest that the public in Great Britain is much more aware of public promotion of the risks of sunlight exposure than its benefits. That said, knowledge about sunlight exposure and vitamin D is fairly strong, though not with respect to the detail of the 'little and often' approach. However, the survey also suggests that levels of sunlight exposure among the public are often excessive. The survey indicates that knowledge and behaviour are both less satisfactory among men and people in lower socio-economic groups. The paper concludes with recommendations for public health communications and for research in this area.

A qualitative study of knowledge, behaviour and attitudes regarding vitamin D acquisition among patients with photosensitivity disorders

BACKGROUND

Cutaneous exposure to sunlight is a major source of vitamin D. Individuals with photosensitivity disorders have symptoms provoked by sunlight and may not achieve the brief sunlight exposures that convey vitamin D acquisition.

OBJECTIVE

To explore knowledge, behaviour and attitudes towards vitamin D and its acquisition in patients with photosensitivity.

METHODS

Patients (n = 19) diagnosed with solar urticaria, erythropoietic protoporphyria or polymorphic light eruption at a specialist photoinvestigation centre participated in semi-structured focus groups to discuss vitamin D knowledge, acquisition behaviours and attitudes towards vitamin D acquisition through sunlight and diet. Discussions were analysed by thematic analysis using MAXQDA11.

RESULTS

Knowledge of vitamin D was variable. There was good awareness that sunlight exposure is an important source but knowledge of dietary sources was poor. Patients had little concern for their own vitamin D status prior to attending the photoinvestigation centre. Most patients avoided sunlight exposure, were unable to achieve the guidance on sun exposure for healthy individuals and were aware this could affect their vitamin D status. Use of oral vitamin D supplements was common, and all were willing to consider supplements if required. Patients recommended improving education of clinicians to increase patient awareness of vitamin D, CONCLUSIONS: More targeted guidance is required on acquisition of vitamin D for patients with photosensitivity, supported by increased patient and clinician education.

Short- and Long-Term Effects of UVA on Arabidopsis Are Mediated by a Novel cGMP Phosphodiesterase

Although UVA radiation (315-400 nm) represents 95% of the UV radiation reaching the earth's surface, surprisingly little is known about its effects on plants [1]. We show that in Arabidopsis, short-term exposure to UVA inhibits the opening of stomata, and this requires a reduction in the cytosolic level of cGMP. This process is independent of UVR8, the UVB receptor. A cGMP-activated phosphodiesterase (AtCN-PDE1) was responsible for the UVA-induced decrease in cGMP in Arabidopsis. AtCN-PDE1-like proteins form a clade within the large HD-domain/PDEase-like protein superfamily, but no eukaryotic members of this subfamily have been functionally characterized. These genes have been lost from the genomes of metazoans but are otherwise conserved as single-copy genes across the tree of life. In longer-term experiments, UVA radiation increased growth and decreased water-use efficiency. These experiments revealed that PDE1 is also a negative regulator of growth. As the PDE1 gene is ancient and not represented in animal lineages, it is likely that at least one element of cGMP signaling in plants has evolved differently to the system present in metazoans.

Is Sunlight Exposure Enough to Avoid Wintertime Vitamin D Deficiency in United Kingdom Population Groups?

Solar ultraviolet radiation (UVR) is required for cutaneous vitamin D synthesis, and experimental studies have indicated the levels of sun exposure required to avoid a vitamin D deficient status. Our objectives are to examine the sun exposure behaviours of different United Kingdom sectors and to identify if their exposure is enough to maintain winter circulating 25-hydroxyvitamin D above deficiency (>25 nmol/L). Data are from a series of human studies involving >500 volunteers and performed using the same protocols in Greater Manchester, UK (53.5° N) in healthy white Caucasian adolescents and working-age adults (skin type I⁻IV), healthy South Asian working-age adults (skin type V), and adults with photodermatoses (skin conditions caused or aggravated by cutaneous sun exposure). Long-term monitoring of the spectral ambient UVR of the Manchester metropolitan area facilitates data interpretation. The healthy white populations are exposed to 3% ambient UVR, contrasting with ~1% in South Asians. South Asians and those with photodermatoses wear clothing exposing smaller skin surface area, and South Asians have the lowest oral vitamin D intake of all groups. Sun exposure levels prevent winter vitamin D deficiency in 95% of healthy white adults and 83% of adolescents, while 32% of the photodermatoses group and >90% of the healthy South Asians were deficient. The latter require increased oral vitamin D, whilst their sun exposure provides a tangible contribution and might convey other health benefits.

Fractional Sunburn Threshold UVR Doses Generate Equivalent Vitamin D and DNA Damage in Skin Types I-VI but with Epidermal DNA Damage Gradient Correlated to Skin Darkness

Public health guidance recommends limiting sun exposure to sub-sunburn levels, but it is unknown whether these can gain vitamin D (for musculoskeletal health) while avoiding epidermal DNA damage (initiates skin cancer). Well-characterized healthy humans of all skin types (I–VI, lightest to darkest skin) were exposed to a low-dose series of solar simulated UVR of 20%–80% their individual sunburn threshold dose (minimal erythema dose). Significant UVR dose responses were seen for serum 25-hydroxyvitamin D and whole epidermal cyclobutane pyrimidine dimers (CPDs), with as little as 0.2 minimal erythema dose concurrently producing 25-hydroxyvitamin D and CPD. Fractional MEDs generated equivalent levels of whole epidermal CPD and 25-hydroxyvitamin D across all skin types. Crucially, we showed an epidermal gradient of CPD formation strongly correlated with skin darkness (r = 0.74, P < 0.0001), which reflected melanin content and showed increasing protection across the skin types, ranging from darkest skin, where high CPD levels occurred superficially, with none in the germinative basal layer, to lightest skin, where CPD levels were induced evenly across the epidermal depth. People with darker skin can be encouraged to use sub-sunburn UVR-exposure to enhance their vitamin D. In people with lighter skin, basal cell damage occurs concurrent with vitamin D synthesis at exquisitely low UVR levels, providing an explanation for their high skin cancer incidence; greater caution is required.

Meeting Vitamin D Requirements in White Caucasians at UK Latitudes: Providing a Choice

The body gains vitamin D through both oral intake (diet/supplementation) and synthesis in skin upon exposure to ultraviolet radiation (UVR). Sun exposure is the major source for most people even though sun exposure is complex and limited by climate and culture. We aimed to quantify the sun exposure required to meet vitamin D targets year-round and determine whether this can be safely achieved in a simply defined manner in the UK as an alternative to increasing vitamin D oral intake. Data from observation (sun exposure, diet, and vitamin D status) and UVR intervention studies performed with white Caucasian adults were combined with modeled all-weather UVR climatology. Daily vitamin D effective UVR doses (all-weather) were calculated across the UK based on ten-year climatology for pre-defined lunchtime exposure regimes. Calculations then determined the time necessary to spend outdoors for the body to gain sufficient vitamin D levels for year-round needs without being sunburnt under differing exposure scenarios. Results show that, in specified conditions, white Caucasians across the UK need nine minutes of daily sunlight at lunchtime from March to September for 25(OH)D levels to remain ≥25 nmol/L throughout the winter. This assumes forearms and lower legs are exposed June-August, while in the remaining, cooler months only hands and face need be exposed. Exposing only the hands and face throughout the summer does not meet requirements.

Serum endocannabinoids and N-acyl ethanolamines and the influence of simulated solar UVR exposure in humans in vivo

Solar ultraviolet radiation (UVR) exposure of human skin has beneficial and harmful effects on health, including impact on immune function, inflammation and reportedly mood, but these are not fully elucidated. Since the endocannabinoid system is implicated in many activities including mood alteration, our objective was to (i) determine and quantify circulating levels of a wide range of endocannabinoid and N-acyl ethanolamine (NAE) species (ii) evaluate whether these are modulated by cutaneous UVR exposures, as attained through repeated low level summer sunlight exposure. Wearing goggles to prevent eye exposure, 16 healthy volunteers (23-59 y; 10 light skin, phototype II, and 6 dark skin, phototype V) received the same UVR exposures (1.3 SED, 95% UVA/5% UVB) thrice weekly for 6 weeks, whilst casually dressed to expose ∼35% skin surface area. Blood samples were taken at baseline, days 1, 3 and 5 of week one, then at weekly intervals, and analysed by LC-MS/MS. Eleven endocannabinoids and NAEs were detected and quantified at baseline, with N-palmitoyl ethanolamine the most abundant (30% of total). Levels did not vary according to phototype (p > 0.05), except for the NAE docosapentaenoyl ethanolamide, which was higher in phototype II than V (p = 0.0002). Level of the endocannabinoid, 2-AG, was elevated during the UVR exposure course (p < 0.05 vs. baseline for all subjects; p < 0.01 for each phototype group), with maximum levels reached by week 2-3, while NAE species did not significantly alter. These findings suggest differential involvement of the cutaneous endocannabinoid system in low dose solar UVR responses in humans.

Duration of Casual Sunlight Exposure Necessary for Adequate Vitamin D Status in Indian Men

OBJECTIVES

To investigate the duration of casual sunlight ultraviolet-B (UVB) exposure required to maintain optimal Vitamin D status (25-hydroxyvitamin-D [25(OH)D]) >50 nmol/L in urban Indian men, using polysulfone (PSU) dosimeters and a sunlight exposure questionnaire.

METHODS

In healthy men (aged 40-60 years) from Pune (18.52° N, 73.86° E), India, serum 25(OH)D was measured using enzyme-linked immunosorbent assay. Sunlight exposure was assessed using PSU dosimeter and by questionnaire.

RESULTS

Of 160 men (48.3 ± 5.6 years), 26.8% were deficient and 40.6% had insufficient Vitamin D concentrations. A hyperbolic function for the relationship between PSU measured sunlight exposure in standard erythema dose (SED) and serum 25(OH)D concentrations (r = 0.87, P < 0.01) revealed that daily exposure of 1 SED was sufficient to maintain serum 25(OH)D concentrations over 50 nmol/L. The curve plateaued around 5 SED (80 nmol/L) and extrapolation of the curve (>5 SED) did not increase 25(OH)D concentrations above 90 nmol/L. Receiver operating curve analysis confirmed that 1 SED-UV exposure was sufficient to maintain 25(OH)D concentrations over 50 nmol/L. Based on the questionnaire data, >1 h of midday casual sunlight exposure was required to maintain serum 25(OH)D concentrations above 50 nmol/L. Duration of sunlight exposure assessed by questionnaire and PSU dosimeter showed a significant correlation (r = 0.517, P < 0.01).

CONCLUSION

In urban Indian men, >1 h of casual midday sunlight exposure daily was required to maintain serum 25(OH)D concentrations above 50 nmol/L, and >2 h of casual sunlight exposure was needed to maintain 25(OH)D concentrations above 75 nmol/L. Excess sunlight did not increase 25(OH)D linearly. The sunlight exposure questionnaire was validated for use in clinical studies and surveys.

A predictive model of serum 25-hydroxyvitamin D in UK white as well as black and Asian minority ethnic population groups for application in food fortification strategy development towards vitamin D deficiency prevention

Within Europe, dark-skinned ethnic groups have been shown to be at much increased risk of vitamin D deficiency compared to their white counterparts. Increasing the dietary supply of vitamin D is potentially the only modifiable environmental component that can be used to prevent vitamin D deficiency among dark-skinned ethnic groups living at high latitude. Empirical data to support development of such strategies is largely lacking. This paper presents the development and validation of an integrated model that may be adapted within the UK population to design fortification strategies for vitamin D, for application in both white and black and Asian minority ethnic (BAME) population groups. Using a step-wise approach, models based on available ultraviolet B (UVB) data, hours of sunlight and two key components (the dose-response of serum 25-hydroxyvitamin D [25(OH)D] to UVB in white and BAME persons and the dose-response of 25(OH)D to vitamin D) were used to predict changes population serum 25(OH)D concentrations throughout the year, stratified by ethnicity, 'via increases' in dietary intake arising from food fortification simulations. The integrated model successfully predicted measured average wintertime 25(OH)D concentrations in addition to the prevalence of serum 25(OH)D <30nmol/L in adult white and BAME individuals (18-70y) in the UK-based National Diet and Nutrition Survey both separately (21.7% and 49.3% predicted versus 20.2% and 50.5% measured, for white and BAME, respectively) and when combined at UK population-relevant proportions of 97% white and 7% BAME (23.2% predicted versus 23.1% measured). Thus this integrated model presents a viable approach to estimating changes in the population concentrations of 25(OH)D that may arise from various dietary fortification approaches.

A qualitative study of the knowledge, behaviour and attitudes of patients with skin cancer regarding sunlight exposure and vitamin D

BACKGROUND

Solar UVR is a major cause of skin cancer but also an important source of vitamin D (VitD), essential for musculoskeletal health. Conflicting public health messages may confuse patients with skin cancer prone to further skin cancer.

OBJECTIVE

To explore the knowledge, behaviour and attitudes of patients with skin cancer to sunlight exposure and VitD sources.

METHODS

Patients (n = 10) previously treated for multiple basal cell cancer in a hospital setting participated in focus group sessions with semi-structured discussions to explore: knowledge of VitD, sun-avoidance behaviour and attitude towards sunlight exposure messages. Thematic data analysis was performed using software programme MAXQDA11.

RESULTS

Pre-existing knowledge of VitD was low. Most patients practised sun avoidance and were not inclined to increase exposure. Patients did not perceive VitD deficiency as a substantial risk to their own health, or a need to take VitD supplements. They aimed to increase VitD status through dietary intake, but knowledge of food VitD content was lacking.

CONCLUSIONS

The patients with skin cancer, appropriate to their heightened skin cancer risk, appeared unlikely to increase their sun exposure to gain VitD. However, education is required regarding the generally low levels of VitD in foodstuffs, and the requirement for supplements/fortified foods if strict sun avoidance is employed.

Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures

Background

The concurrent impact of repeated low‐level summer sunlight exposures on vitamin D production and cutaneous DNA damage, potentially leading to mutagenesis and skin cancer, is unknown.

Objectives

This is an experimental study (i) to determine the dual impact of repeated low‐level sunlight exposures on vitamin D status and DNA damage/repair (via both skin and urinary biomarkers) in light‐skinned adults; and (ii) to compare outcomes following the same exposures in brown‐skinned adults.

Methods

Ten white (phototype II) and six South Asian volunteers (phototype V), aged 23–59 years, received 6 weeks’ simulated summer sunlight exposures (95% ultraviolet A/5% ultraviolet B, 1·3 standard erythemal doses three times weekly) wearing summer clothing exposing ~35% body surface area. Assessments made were circulating 25‐hydroxyvitamin D [25(OH)D], immunohistochemistry for cyclobutane pyrimidine dimer (CPD)‐positive nuclei and urinary biomarkers of direct and oxidative (8‐oxo‐deoxyguanosine) DNA damage.

Results

Serum 25(OH)D rose from mean 36·5 ± 13·0 to 54·3 ± 10·5 nmol L⁻¹ (14·6 ± 5·2 to 21·7 ± 4·2 ng mL⁻¹) in phototype II vs. 17·2 ± 6·3 to 25·5 ± 9·5 nmol L⁻¹ (6·9 ± 2·5 to 10·2 ± 3·8 ng mL⁻¹) in phototype V (P < 0·05). Phototype II skin showed CPD‐positive nuclei immediately postcourse, mean 44% (range 27–84) cleared after 24 h, contrasting with minimal DNA damage and full clearance in phototype V (P < 0·001). The findings did not differ from those following single ultraviolet radiation (UVR) exposure. Urinary CPDs remained below the detection threshold in both groups; 8‐oxo‐deoxyguanosine was higher in phototype II than V (P = 0·002), but was unaffected by UVR.

Conclusions

Low‐dose summer sunlight exposures confer vitamin D sufficiency in light‐skinned people concurrently with low‐level, nonaccumulating DNA damage. The same exposures produce minimal DNA damage but less vitamin D in brown‐skinned people. This informs tailoring of sun‐exposure policies.

What's already known about this topic?

Repeated low‐level exposures to simulated U.K. sunlight can produce vitamin D sufficiency in light‐skinned people, but the concurrent impact on cutaneous DNA damage is unknown.

What does this study add?

Low‐level simulated sunlight exposures in people of skin phototype II conferred vitamin D sufficiency concurrently with DNA damage, which showed partial clearance at 24 h and no evidence of accumulated damage after 6 weeks of exposures.

The same exposures produced minimal DNA damage but less vitamin D in brown‐skinned people (phototype V).

The findings are informative for sun‐exposure guidance.

Plain language summary available online

Sun Exposure Behavior, Seasonal Vitamin D Deficiency, and Relationship to Bone Health in Adolescents

CONTEXT

Vitamin D is essential for bone health in adolescence, when there is rapid bone mineral content accrual. Because cutaneous sun exposure provides vitamin D, there is no recommended oral intake for UK adolescents.

OBJECTIVE

Our objective was to assess seasonal vitamin D status and its contributors in white Caucasian adolescents and examine bone health in those found deficient.

DESIGN

Prospective cohort study was undertaken.

SETTING

Six schools in Greater Manchester, UK, were included.

PARTICIPANTS

Participants were 131 adolescents between 12 and 15 years of age.

INTERVENTION(S)

Seasonal assessment of circulating 25-hydroxyvitamin D (25OHD), personal sun exposure, and dietary vitamin D. Adolescents deficient (25OHD <10 ng/ml/25 nmol/liter) in at least one season underwent dual-energy X-ray absorptiometry (lumbar spine, femoral neck), with bone mineral apparent density correction for size, and peripheral quantitative computed tomography (distal radius) for volumetric bone mineral density (BMD).

MAIN OUTCOME MEASURE

Serum 25OHD and BMD measurements.

RESULTS

Mean 25OHD was highest in September: 24.1 (SD, 6.9) ng/ml and lowest in January: 15.5 (5.9) ng/ml. Over the year, 16% were deficient in ≥ one season and 79% insufficient (25OHD <20 ng/ml/50 nmol/liter) including 28% in September. Dietary vitamin D was low year-round, whereas personal sun exposure was seasonal and predominantly across the school week. Holidays accounted for 17% variation in peak 25OHD (P < .001). Nineteen adolescents underwent bone assessment, which showed low femoral neck bone mineral apparent density vs matched reference data (P = .0002), three with Z less than or equal to -2.0 distal radius trabecular volumetric BMD.

CONCLUSIONS

Sun exposure levels failed to provide adequate vitamin D, with approximately one-quarter of adolescents insufficient even at summer peak. Seasonal vitamin D deficiency was prevalent and those affected had low BMD. Recommendations on vitamin D acquisition are indicated in this age-group.

Early skin and challenge testing after rocuronium anaphylaxis

We present a case of early skin and challenge testing in a patient following severe anaphylaxis to rocuronium. The patient presented for semi-elective laparoscopic cholecystectomy and developed anaphylaxis with severe cardiovascular collapse after induction of anaesthesia. Surgery was cancelled but was considered necessary before the recommended four to six weeks for formal allergy testing. Limited skin and challenge testing was performed to rocuronium and cisatracurium while the patient was in the intensive care unit to identify a safe neuromuscular blocking drug for subsequent early surgery. The subsequent surgery, 48 hours after the initial reaction, was uneventful. The case highlights the difficulties when anaesthetising patients with recent anaphylaxis who have not yet had formal allergy testing and presents a potential management strategy involving early skin testing.

An Integrated Predictive Model of Population Serum 25-Hydroxyvitamin D for Application in Strategy Development for Vitamin D Deficiency Prevention

BACKGROUND

To enable food-based strategies for the prevention of vitamin D deficiency to be evidence-based, there is a need to develop integrated predictive models of population serum 25-hydroxyvitamin D [25(OH)D] that are responsive to both solar and dietary inputs of vitamin D.

OBJECTIVES

The objectives of this work were to develop and validate an integrated mathematical model with the use of data on UVB availability, exposure, and dietary intake to predict serum 25(OH)D concentrations in a nationally representative sample of adults, and then test the model's performance with the use of 3 hypothetical fortification scenarios as exemplars.

METHODS

Data on UVB availability and hours of sunlight in Ireland were used in a mathematical model to predict serum 25(OH)D in Irish adults aged 18-64 y. An equation from our dose-related vitamin D supplementation trial in adults was developed and integrated into the model, which allowed us to predict the impact of changes in dietary vitamin D on the contribution to annual serum 25(OH)D concentrations, accounting for seasonality of UVB availability. Recently published estimates of the impact of 3 vitamin D food fortification scenarios on vitamin D intake in a representative sample of Irish adults were used in the model as a test.

RESULTS

The UVB- and vitamin D intake-serum 25(OH)D components of the integrated model were both validated with the use of independent data. The model predicted that the percentage of vitamin D deficiency [serum 25(OH)D <30 nmol/L] in the adult population during an extended winter period was 18.1% (vs. 18.6% measured), which could be reduced in a stepwise manner with the incorporation of an increased number of vitamin D-fortified foods, down to 6.6% with the inclusion of enhanced fortified dairy-related products, fat spreads, fruit juice and drinks, and cereal products.

CONCLUSION

Mathematical models have the ability to inform how vitamin D food fortification in various constructs may affect population serum 25(OH)D concentrations and the prevalence of vitamin D deficiency.

Colour as a signal for entraining the mammalian circadian clock

Twilight is characterised by changes in both quantity (“irradiance”) and quality (“colour”) of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue–yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision.

Environmental measurements and physiological recordings reveal that mice not only use changes in the intensity of sunlight to entrain their circadian clock, but also employ blue–yellow color discrimination to detect spectral changes associated with dawn and dusk.

Animals use an internal brain clock to keep track of time and adjust their behaviour in anticipation of the coming day or night. To be useful, however, this clock must be synchronised to external time. Assessing external time is typically thought to rely on measuring large changes in ambient light intensity that occur over dawn/dusk. The colour of light also changes over these twilight transitions, but it is currently unknown whether such changes in colour are important for synchronising biological clocks to the solar cycle. Here we show that the mammalian blue–yellow colour discrimination axis provides a more reliable indication of twilight progression than a system solely measuring changes in light intensity. We go on to use electrical recordings from the brain clock to reveal the presence of many neurons that can track changes in blue–yellow colour occurring during natural twilight. Finally, using mice housed under lighting regimes with simulated dawn/dusk transitions, we show that changes in colour are required for appropriate biological timing with respect to the solar cycle. In sum, our data reveal a new sensory mechanism for estimating time of day that should be available to all mammals capable of chromatic vision, including humans.

A modeling approach to determine how much UV radiation is available across the UK and Ireland for health risk and benefit studies

Monthly average vitamin D effective UV doses (J m⁻²) over UK based on data for years 2003–2012. The southern part receives 1.5–2 times more UV than the north during spring, summer and autumn. Doses at coastal sites being up to 25% higher than inland areas.

Sunlight exposure behaviour and vitamin D status in photosensitive patients: longitudinal comparative study with healthy individuals at U.K. latitude

BACKGROUND

Low vitamin D status is prevalent in wintertime in populations at northerly latitudes. Photosensitive patients are advised to practise sun avoidance, but their sunlight exposure levels, photoprotective measures and resulting vitamin D status are unknown.

OBJECTIVES

To examine seasonal vitamin D status in photosensitive patients relative to healthy individuals and to assess quantitatively behavioural and demographic contributors.

METHODS

This was a longitudinal prospective cohort study (53·5°N) examining year-round 25-hydroxyvitamin D [25(OH)D] levels, sun-exposure behaviour and oral vitamin D intake in photosensitive patients diagnosed at a photoinvestigation unit (n = 53), compared with concurrently assessed healthy adults (n = 109).

RESULTS

Photosensitive patients achieved seasonal 25(OH)D variation, but insufficient (< 20 ng mL(-1); 50 nmol L(-1)) and even deficient (< 10 ng mL(-1); 25 nmol L(-1)) levels occurred at the summer peak in 47% and 9% of patients, respectively, rising to 73% and 32% at the winter trough. Adjusting for demographic factors, the mean values were lower than for healthy volunteers by 18% [95% confidence interval (CI) 4-29] in summer (P = 0·02) and 25% (95% CI 7-39) in winter (P = 0·01). Behavioural factors explained 25(OH)D differences between cohorts. Patients demonstrated lower weekend ultraviolet B doses (P < 0·001), smaller skin surface area exposure (P = 0·004) and greater sunscreen use (P < 0·001), while average oral vitamin D intake was low in both groups (photosensitive: 2·94 μg per day). Supplementation and summer surface area exposure predicted summer peak and winter trough 25(OH)D levels. A 1 μg per day increment in supplementary vitamin D raised summer and winter 25(OH)D by 5% (95% CI 3-7) and 9% (95% CI 5-12), respectively (both P < 0·001).

CONCLUSIONS

Photosensitive patients are, through their photoprotective measures, at high risk of year-round low vitamin D status. Guidance on oral measures should target this patient group and their physicians.

Sunlight exposure and photoprotection behaviour of white Caucasian adolescents in the UK

BACKGROUND

Sun exposure has positive and negative effects on health, yet little is known about the sun exposure behaviour of UK adolescents, including those more prone or less prone to sunburn.

OBJECTIVE

To examine sun exposure behaviour of UK white Caucasian adolescents including time spent outdoors, holiday behaviour, use of sunscreen and clothing, with assessment for differences between sun-reactive skin type groups.

METHODS

White Caucasian adolescents (12-15 years) attending schools in Greater Manchester completed a two-page questionnaire to assess sun exposure and photoprotective behaviour.

RESULTS

A total of 133 adolescents (median age 13.4 years; 39% skin type I/II, 61% skin type III/IV) completed the questionnaire. In summer, adolescents spent significantly longer outdoors at weekends (median 4 h/day, range 0.25-10) than on weekdays (2, 0.25-6; P < 0.0001). When at home in the UK during summer, 44% reported never wearing sunscreen compared to just 1% when on a sunny holiday. Sunscreen use was also greater (frequency/coverage) when on a sunny holiday than at home in the UK summer (P < 0.0001). Adolescents of skin types I/II (easy burning) spent significantly less time outdoors than skin types III/IV (easy tanning) on summer weekends (P < 0.001), summer weekdays (P < 0.05) and on a sunny holiday (P = 0.001). Furthermore, skin types I/II reported greater sunscreen use during summer in the UK and on sunny holiday (both P < 0.01), and wore clothing covering a greater skin area on a sunny holiday (P < 0.01) than skin types III/IV. There was no difference in sun exposure behaviour/protection between males and females.

CONCLUSION

The greater sun-protective measures reported by adolescents of sun-reactive skin type group I/II than III/IV suggest those who burn more easily are aware of the greater need to protect their skin. However, use of sunscreen during the UK summer is low and may need more effective promotion in adolescents.

Lifestyle factors including less cutaneous sun exposure contribute to starkly lower vitamin D levels in U.K. South Asians compared with the white population

BACKGROUND

Long-standing concerns over the vitamin D status of South Asian adults in the U.K. require studies using statistically valid sample sizes to measure annual variation and contributory lifestyle factors.

OBJECTIVES

To measure annual variation in the vitamin D status of U.K. South Asians, to determine the associated lifestyle influences, and to compare these with a similar study of white adults.

METHODS

A single-centre, prospective cohort study measuring circulating 25-hydroxyvitamin D [25(OH)D], sunlight exposure levels and lifestyle factors for 1 year in 125 ambulant South Asian adults with sun-reactive skin type V, aged 20-60 years, in Greater Manchester, U.K. (53·5°N).

RESULTS

The 25(OH)D levels of South Asians were alarmingly low. In summer, their median 25(OH)D level was 9·0 ng mL(-1) , [interquartile range (IQR) 6·7-13·1], falling to 5·8 ng mL(-1) (IQR 4·0-8·1) in winter. This compared with values in the white population of 26·2 ng mL(-1) (IQR 19·9-31·5) in summer and 18·9 ng mL(-1) IQR (11·6-23·7) in winter. Median daily dietary vitamin D was lower in South Asians (1·32 μg vs. 3·26 μg for white subjects) and was compounded by low supplement use. Despite similar times spent outdoors, ultraviolet (UV) dosimeters recorded lower personal UV exposure among South Asians, indicating sun avoidance when outside, while sun exposure diaries recorded lower amounts of skin surface exposure.

CONCLUSIONS

The majority of South Asians never reached sufficiency in vitamin D status. Lifestyle differences, with lower oral intake, sun exposure and rates of cutaneous production due to darker skin, indicate that standard advice on obtaining sufficient vitamin D needs modification for the South Asian community in the U.K.

Influence of external, intrinsic and individual behaviour variables on serum 25(OH)D in a German survey

The objective of the present study was to identify external, intrinsic or behavioural factors that significantly influenced serum 25-hydroxyvitamin D (25(OH)D) concentrations in a German survey. Data from 3061 participants in the Cooperative Health Research in the Region of Augsburg, Germany (KORA) F4 survey were used to relate potential determinants to measured mean serum 25(OH)D concentrations using multivariable regression models. The factors significantly associated with hypovitaminosis D (defined as 25(OH)D<25 nmolL(-1)) were season (winter, spring and autumn), urban environment and high body mass index. In contrast, times spent in sunny regions, hours per day spent outdoors in the summer as well as additional oral intake were associated with higher 25(OH)D concentrations. These results suggest that mainly ambient UV exposure but also individual behaviour are the most important determinants for personal 25(OH)D concentrations. The analyses further showed that in winter 43% of subjects were vitamin D deficient and 42% insufficient. Even in summer over half the population has insufficient vitamin D status with 8% deficient and 47% insufficient. Therefore measures to mitigate widespread vitamin D insufficiency such as regular short-term sun exposure and/or improved dietary intake/supplementation recommendations by public health bodies need to be considered.

Ultraviolet exposure scenarios: risks of erythema from recommendations on cutaneous vitamin D synthesis

Exposure to sunlight is a major source of vitamin D for most people yet public health advice focuses overwhelmingly on avoiding exposure of unprotected skin because of the risks oferythema and skin cancer. We have calculated the exposure required to gain a number of proposed oral-equivalent doses of vitamin D, as functions of latitude, season, skin type and skin area exposed, together with the associated risk of erythema, expressed in minimum erythema doses. The model results show that the current recommended daily intake of 400 IU is readily achievable through casual sun exposure in the midday lunch hour, with no risk of erythema, for all latitudes some of the year and for all the year at some (low) latitudes. At the higher proposed vitamin D dose of 1000 IU lunchtime sun exposure is still a viable route to the vitamin, but requires the commitment to expose greater areas of skin, or is effective for a shorter period of the year. The highest vitamin D requirement considered was 4000 IU per day. For much of the globe and much of the year, this is not achievable in a lunchtime hour and where it is possible large areas of skin must be exposed to prevent erythema. When the only variable considered was skin type, latitudinal and seasonal limits on adequate vitamin D production were more restrictive for skin type 5 than skin type 2.

Efficacy of a dose range of simulated sunlight exposures in raising vitamin D status in South Asian adults: implications for targeted guidance on sun exposure

BACKGROUND

Vitamin D is essential for bone health, and cutaneous synthesis is an important source. South Asians cannot attain adequate amounts of vitamin D by following general recommendations on summer sunlight exposure at northerly latitudes, and increased exposure may be appropriate for improving their vitamin D status.

OBJECTIVE

We examined the efficacy of a dose range of simulated summer sunlight exposures in raising vitamin D status in UK adults of South Asian ethnicity.

DESIGN

In a dose-response study, healthy adults of South Asian ethnicity (n = 60; 20-60 y old) received 1 of 6 ultraviolet exposures ranging from 0.65 to 3.9 standard erythema doses (SEDs), which were equivalent to 15-90 min unshaded noontime summer sunlight at 53.5°N (Manchester, United Kingdom), 3 times/wk for 6 wk, while wearing casual clothes that revealed a 35% skin area. Serum 25-hydroxyvitamin D [25(OH)D] was measured weekly, and dietary vitamin D was estimated.

RESULTS

At baseline, all completing participants (n = 51) were vitamin D insufficient [25(OH)D concentrations <20 ng/mL], and a high proportion of participants were deficient [35% of subjects had 25(OH)D concentrations <5 ng/mL, and 90% of subjects had 25(OH)D concentrations <10 ng/mL, which are concentrations at which osteomalacia and rickets occur). The 25(OH)D concentration rose significantly in all dose groups. Postcourse, all participants achieved 25(OH)D concentrations ≥5 ng/mL, whereas only 6 subjects attained 25(OH)D concentrations ≥20 ng/mL. Participants who received exposures ≥1.95 SEDs (equivalent to 45 min unshaded sunlight; n = 33) attained a mean (±SD) 25(OH)D concentration of 15.7 ± 5 ng/mL (mean rise: 8.7 ± 5.7 ng/mL; 95% CI: 6.8, 10.6 ng/mL; P < 0.001), and 94% of subjects achieved concentrations >10 ng/mL.

CONCLUSIONS

Targeted guidance on sunlight exposure could usefully enhance vitamin D status to avoid deficiency [25(OH)D concentration >10 ng/mL] in South Asians living at latitudes distant from the equator. This trial was registered at the ISRCTN Register (www.isrctn.org) as 07565297.

Recommended summer sunlight exposure amounts fail to produce sufficient vitamin D status in UK adults of South Asian origin

BACKGROUND

The cutaneous synthesis of vitamin D is dependent on UVB from sunlight, but melanin reduces the penetration of UVB and thus contributes to vitamin D insufficiency in individuals with darker skin. The national guidance provided on amounts of sunlight exposure in the United Kingdom is for the light-skinned population, and in the absence of dedicated information, darker-skinned people may attempt to follow this guidance.

OBJECTIVES

We determined the relative effect of a simulation of UK recommendations of summer sunlight exposure on the vitamin D status of individuals of South Asian ethnicity compared with that of whites.

DESIGN

In a prospective cohort study, simulated summer sunlight exposures were provided under rigorous dosimetric conditions to 15 adults (aged 20-60 y) of South Asian ethnicity, and serum 25-hydroxyvitamin D [25(OH)D] was measured weekly. Dietary vitamin D intake was estimated. Outcomes were compared with those of 109 whites (aged 20-60 y) treated with the identical UV-radiation exposure protocol.

RESULTS

At baseline (winter trough), all South Asians were vitamin D-insufficient [25(OH)D concentrations <20 ng/mL], and 27% of South Asians were vitamin D-deficient [25(OH)D concentrations <5 ng/mL]; although 25(OH)D concentrations increased postcourse (P < 0.0001), all South Asians remained vitamin D-insufficient. The mean increase in 25(OH)D was 4.3 compared with 10.5 ng/mL in the South Asian and white groups, respectively (P < 0.0001), and 90% of the white group reached vitamin D sufficiency postcourse. The median dietary vitamin D intake was very low in both groups.

CONCLUSIONS

Sunlight-exposure recommendations are inappropriate for individuals of South Asian ethnicity who live at the UK latitude. More guidance is required to meet the vitamin D requirements of this sector of the population. This study was registered at www.isrctn.org as ISRCTN 07565297.

Know your standard: clarifying the CIE erythema action spectrum

The standard erythema action spectrum provides an internationally accepted representation of the erythema-inducing effectiveness of wavelengths in the UV part of the spectrum. The action spectrum forms the basis of the UV index used for public health information, defines the standard erythema dose unit and the minimum erythema dose and is the default response spectrum aspired to by a range of UV radiometer manufacturers. However, there are several versions of this erythema action spectrum in use, and only one of them has been endorsed as a standard. While the differences in erythemally weighted radiation incurred by choice of action spectrum will be no more than a few percent, this uncertainty is unnecessary. Here we detail the differences in the different versions of erythema action spectra, illustrate the resulting effects in quantifying UV doses and encourage readers to use only the standard version of the action spectrum in the future.

The role of sunlight exposure in determining the vitamin D status of the U.K. white adult population

BACKGROUND

Vitamin D is necessary for bone health and is potentially protective against a range of malignancies. Opinions are divided on whether the proposed optimal circulating 25-hydroxyvitamin D [25(OH)D] level (≥ 32 ng mL⁻¹) is an appropriate and feasible target at population level.

OBJECTIVES

We examined whether personal sunlight exposure levels can provide vitamin D sufficient (≥ 20 ng mL⁻¹) and optimal status in the U.K. public.

METHODS

This prospective cohort study measured circulating 25(OH)D monthly for 12 months in 125 white adults aged 20-60 years in Greater Manchester. Dietary vitamin D and personal ultraviolet radiation (UVR) exposure were assessed over 1-2 weeks in each season. The primary analysis determined the post-summer peak 25(OH)D required to maintain sufficiency in wintertime.

RESULTS

Dietary vitamin D remained low in all seasons (median 3·27 μg daily, range 2·76-4·15) while personal UVR exposure levels were high in spring and summer, low in autumn and negligible in winter. Mean 25(OH)D levels were highest in September [28·4 ng mL⁻¹; 28% optimal, zero deficient (<5 ng mL⁻¹)], and lowest in February (18·3 ng mL⁻¹; 7% optimal, 5% deficient). A February 25(OH)D level of 20 ng mL⁻¹ was achieved following a mean (95% confidence interval) late summer level of 30·4 (25·6-35·2) and 34·9 (27·9-41·9) ng mL⁻¹ in women and men, respectively, with 62% of variance explained by gender and September levels.

CONCLUSIONS

Late summer 25(OH)D levels approximating the optimal range are required to retain sufficiency throughout the U.K. winter. Currently the majority of the population fails to reach this post-summer level and becomes vitamin D insufficient during the winter.

The impact of photosensitivity disorders on aspects of lifestyle

BACKGROUND

Photosensitivity disorders involve an abnormal skin reaction to sunlight exposure and affect a substantial percentage of the population. No previous studies have directly compared lifestyle attributes between photosensitive and healthy individuals.

OBJECTIVES

To assess the impact of photosensitivity on time spent outdoors in the U.K., holiday behaviour, use of sunscreens and vitamin D supplements, and employment status.

METHODS

Questionnaires were completed by ambulant photosensitive and healthy adults aged 18-60 years residing in Greater Manchester.

RESULTS

Forty-five adults with moderate-severe photosensitivity and 124 healthy adults completed the questionnaire. This revealed that photosensitive subjects spent significantly less time outdoors in the U.K. on both summer weekdays (P < 0·01) and summer weekends (P < 0·0001) than healthy subjects, took fewer holidays per year (P < 0·05), and spent less time outdoors on a sunny holiday (P < 0·0001). They wore clothing that covered a wider skin area (P < 0·0001), and use of sunscreen was greater (both frequency of application and area covered) in the photosensitive group outside of holiday time (P < 0·0001), but not when on a sunny holiday, as healthy people increased their sunscreen use at this time. Despite the reduced sun exposure, photosensitive subjects were no more likely to take vitamin D supplements than healthy subjects were; they also exhibited a significantly higher rate of unemployment (P < 0·05).

CONCLUSIONS

Photosensitivity disorders negatively influence lifestyle including employment status; more attention is required to the socioeconomic impact of these conditions.

Potential of wind turbines to elicit seizures under various meteorological conditions

PURPOSE

To determine the potential risk of epileptic seizures from wind turbine shadow flicker under various meteorologic conditions.

METHODS

We extend a previous model to include attenuation of sunlight by the atmosphere using the libradtran radiative transfer code.

RESULTS

Under conditions in which observers look toward the horizon with their eyes open we find that there is risk when the observer is closer than 1.2 times the total turbine height when on land, and 2.8 times the total turbine height in marine environments, the risk limited by the size of the image of the sun's disc on the retina. When looking at the ground, where the shadow of the blade is cast, observers are at risk only when at a distance <36 times the blade width, the risk limited by image contrast. If the observer views the horizon and closes their eyes, however, the stimulus size and contrast ratio are epileptogenic for solar elevation angles down to approximately 5 degrees.

DISCUSSION

Large turbines rotate at a rate below that at which the flicker is likely to present a risk, although there is a risk from smaller turbines that interrupt sunlight more than three times per second. For the scenarios considered, we find the risk is negligible at a distance more than about nine times the maximum height reached by the turbine blade, a distance similar to that in guidance from the United Kingdom planning authorities.

Calculated ultraviolet exposure levels for a healthy vitamin D status

The dangers of overexposure to sunlight have been well publicized, but less attention has been given to an acknowledged benefit of exposure to UV radiation; that being the cutaneous synthesis of vitamin D3. Here we define a standard vitamin D dose on the basis of recently recommended requirements for vitamin D that take account of its risk reduction role in a variety of diseases, and present a web-based tool that enables the reader to calculate associated exposure times for any time and place using either default values or user-selected conditions. Either it is not possible to synthesize vitamin D3 at high latitudes in winter, or the exposure time required to reach a standard dose is sometimes impractical. Where solar UV is sufficient, a risk-benefit analysis of sunburn vs. vitamin D3 synthesis shows that the best time for brief sun exposure is in the middle of the day. For low solar elevation angles common at high latitudes, a fine line exists between adequate UV exposure for vitamin D3 synthesis and a risk of sun burn.

Who, what, where and when-influences on cutaneous vitamin D synthesis

The synthesis of vitamin D in skin is a two-stage process that begins with the production of previtamin D after irradiation of 7-dehydrocholesterol by ultraviolet (UV) radiation. A number of personal and environmental factors control the probability of a suitable UV photon reaching a molecule of 7-dehydrocholesterol in the skin. These are astronomical factors that govern the solar zenith angle (SZA), and the local state of the atmosphere, determining the available solar UV radiation; skin pigmentation and age, determining competing absorbers of UV radiation and available 7-dehydrocholesterol; individual behaviour in the local surroundings, determining exposure of unprotected skin to available UV radiation. The only one of these influences that can be determined unequivocally for any situation is the SZA. The other influences must be considered either as individual case studies, or be represented by "typical" and "idealised" situations for the weather, skin and behaviour. At large SZAs there is insufficient solar UV radiation to initiate significant vitamin D synthesis. At smaller SZAs assessment of solar exposure necessary for vitamin D synthesis can only be indicative and application of any such assessment necessarily requires awareness of both self- and the local environment.

A Web-based tool for UV irradiance data: predictions for European and Southeast Asian sites

There are a range of UV models available, but one needs significant pre-existing knowledge and experience in order to be able to use them. In this article a comparatively simple Web-based model developed for the SoDa (Integration and Exploitation of Networked Solar Radiation Databases for Environment Monitoring) project is presented. This is a clear-sky model with modifications for cloud effects. To determine if the model produces realistic UV data the output is compared with 1 year sets of hourly measurements at sites in the United Kingdom and Thailand. The accuracy of the output depends on the input, but reasonable results were obtained with the use of the default database inputs and improved when pyranometer instead of modeled data provided the global radiation input needed to estimate the UV. The average modeled values of UV for the UK site were found to be within 10% of measurements. For the tropical sites in Thailand the average modeled values were within 1120% of measurements for the four sites with the use of the default SoDa database values. These results improved when pyranometer data and TOMS ozone data from 2002 replaced the standard SoDa database values, reducing the error range for all four sites to less than 15%.

Portable device for characterizing the angular response of UV spectroradiometers

This paper introduces a device that was developed to measure the angular response of UV spectroradiometers in the field. This device is designed to be used at the operating position of spectroradiometers; thus the derived angular response also includes any effects from imperfect leveling of the diffuser and corresponds to the actual operational angular response. The design and characterization of the device and the results from its application on 11 different spectroradiometers that operate at different European UV stations are presented. Various sources of uncertainties that were identified result in a combined uncertainty in determining the angular response, which ranges between approximately 1.5% and 10%, depending on the incidence angle and the characteristics of the diffuser. For the 11 instruments, the error in reporting the diffuse irradiance ranges between 2% and - 13%, assuming isotropic distribution of the downwelling radiances.

Traveling reference spectroradiometer for routine quality assurance of spectral solar ultraviolet irradiance measurements

A transportable reference spectroradiometer for measuring spectral solar ultraviolet irradiance has been developed and validated. The expanded uncertainty of solar irradiance measurements with this reference spectroradiometer, based on the described methodology, is 8.8% to 4.6%, depending on the wavelength and the solar zenith angle. The accuracy of the spectroradiometer was validated by repeated site visits to two European UV monitoring sites as well as by regular comparisons with the reference spectroradiometer of the European Reference Centre for UV radiation measurements in Ispra, Italy. The spectral solar irradiance measurements of the Quality Assurance of Spectral Ultraviolet Measurements in Europe through the Development of a Transportable Unit (QASUME) spectroradiometer and these three spectroradiometers have agreed to better than 6% during the ten intercomparison campaigns held from 2002 to 2004. If the differences in irradiance scales of as much as 2% are taken into account, the agreement is of the order of 4% over the wavelength range of 300-400 nm.

Quality assurance of reference standards from nine European solar-ultraviolet monitoring laboratories

A program for quality assurance of reference standards has been initiated among nine solar-UV monitoring laboratories. By means of a traveling lamp package that comprises several 1000-W ANSI code DXW-type quartz-halogen lamps, a 0.1-ohm shunt, and a 6-1/2 digit voltmeter, the irradiance scales used by the nine laboratories were compared with one another; a relative uncertainty of 1.2% was found. The comparison of 15 reference standards yielded differences of as much as 9%; the average difference was less than 3%.