Erythemal UVB Research Articles

An empirical correlation between erythemal UVB and global irradiation developed for a single site and tested at two sites in Israel

An empirical correlation to predict the terrestrial erythemal UVB irradiation under all sky conditions as a function of a single measured parameter, global irradiation, which is available at most meteorological stations is proposed. A database consisting of measurements performed in Beer Sheva between 1996 and 2018 was divided into two sets. A primary data set consisting of measurements between 1996 and 2011 (5553 days) was utilized to develop the empirical correlation. Two secondary data sets consisting of measurements performed at Beer Sheva (1272 days) and Neve Zohar (1047 days) between January 2012 and September 2018 were used to validate the correlation. The results of the statistical analysis of the primary data reported in terms of %MBE, %RMSE, and the correlation coefficient R were − 0.01, 14.85, and 0.947, respectively. The statistical analysis for the validation procedures gives the following results: %MBE, %RMSE, and R for Beer Sheva were − 0.57, 19.80, and 0.914, respectively, and 0.95, 18.49, and 0.950 for Neve Zohar, respectively. An inter-comparison between the results of the statistical analysis of the present empirical correlation with those for previously proposed correlations, requiring more measured/calculated parameters, exhibited essentially the same degree of agreement between calculated and measured values.

Hybrid Diffuse Reflectance Spectroscopy: Non-Erythemal in vivo Testing of Sun Protection Factor

Background/Aims: In order to define a label sun protection factor (SPF) of topically applied sunscreens, in vivo test methods like ISO 24444, FDA guideline, or the Australian standard are used worldwide. The basis of all these methods is provoking an erythemal skin reaction by UV irradiation to find the level of unprotected and protected minimal erythemal doses (MED). In vitro methods replacing the human skin by any kind of non-human material are still not available. Thus, offering the new hybrid diffuse reflectance spectroscopy (HDRS) technique that is able to stay on an in vivo level for SPF testing but meanwhile neglecting the UV-dose-related erythemal skin reaction is a perfect combination to take care of sun protection and any ethical concerns in SPF testing nowadays. Methods: HDRS is a combination of in vivo diffuse reflectance spectroscopy (DRS) measurements on the skin and in vitro transmission measurements of a sunscreen on a roughened polymethylmethacrylate plate. By this technique, the in vivo behavior of the investigated sunscreen on the skin is measured as well as the UVB absorption, which is still non-visible in the reflectance technique. In order to establish an alternative method for in vivo SPF testing, a huge number of sunscreens (80 samples) was measured by HDRS and compared to the worldwide accepted standard ISO 24444. The variety of sunscreens measured reflects a wide range of different types of formulations as well as a wide range of SPFs (5–120) to validate this new alternative SPF testing procedure. Results: The applied quantity of product as well as skin color dependencies of signal generation are shown to support any basic correlation of DRS signal generation and sun protection expectations. Far-reaching statistical data analyses show an excellent link of the new non-erythemally driven HDRS-SPF technique and ISO 24444 results. In the same way, HDRS-UVA-PF results can be correlated with UVA-PF values calculated from ISO 24443. Conclusion: Due to the elimination of any erythemal relevant UVB and UVA doses, absolutely no skin reaction occurs. Consequently there is no need to define a MED any more. For the first time an alternative way to SPF is shown without any ethical concerns of SPF testing in vivo and/or any restriction of SPF testing in vitro. Regardless of the type of formulation or the level of protection, an excellent correlation of SPF_HDRS and SPF₂₄₄₄₄ for sunscreen labeling could be found. By this new alternative non-erythemal technique, not only SPF values can be measured, but also UVA-PF values can be calculated with an excellent correlation to ISO 24443 from the same set of data. For the first time a robust alternative test method of SPF- and UVA-PF values is described, taking into account the interaction of sunscreen formulation and skin.

Impact of Ultraviolet Radiation on Expression of Transforming Growth Factor β, Smad2, Metalloproteinases-1, -3, -8, -9, Cathepsin K and Progerin.

Ultraviolet radiation (UVR) is one of the most important environmental factors involved in photoaging. Exposure to UVR leads to dysregulation of expression of cell cycle-related proteins which play key role in skin photodegradation that pretends to develop carcinogenesis. This study examines the role of various UVB doses on the expression of transforming growth factor beta (TGF-β), Smad2, cathepsin K, progerin and matrix metalloproteinases (MMPs)-1,-3,-8,-9. A group consisting of 63 healthy individuals underwent one of the following treatments: (1) whole body exposed to UVB irradiation on each of 10 consecutive days with 0.7 MED, or (2) whole-body irradiation as described followed by a single erythemal UVB dose on a small body area, or (3) irradiated only with a single erythemal UVB dose on small body area, or (4) were not irradiated at all (control group). When we compared all irradiated groups to the control group, there was significantly higher expression of TGF-β, MMP-1,-3,-9 and cathepsin K proteins evaluated by Western blot method. The results suggest the role of UVB in impairment of proteins expression that is involved in cell cycle's regulation. Changes in the protein expression involved by acute and chronic UVR confirm its essential role in skin photodestruction. Moreover, obtained result indicates the tendency to occurrence of photoadaptation phenomenon.

Influence of low ozone episodes on erythemal UV-B radiation in Austria

This study investigates the influence of low ozone episodes on UV-B radiation in Austria during the period 1999 to 2015. To this aim observations of total column ozone (TCO) in the Greater Alpine Region (Arosa, Switzerland; Hohenpeissenberg, Germany; Hradec Kralove, Czech Republic; Sonnblick, Austria), and erythemal UV-B radiation, available from 12 sites of the Austrian UV-B monitoring network, are analyzed. As previous definitions for low ozone episodes are not particularly suited to investigate effects on UV radiation, a novel threshold approach—considering anomalies—is developed to provide a joint framework for the analysis of extremes. TCO and UV extremes are negatively correlated, although modulating effects of sunshine duration impact the robustness of the statistical relationship. Therefore, information on relative sunshine duration (SDrel), available at (or nearby) UV-B monitoring sites, is included as explanatory variable in the analysis. The joint analysis of anomalies of both UV index (UVI) and total ozone (∆UVI, ∆TCO) and SDrel across sites shows that more than 65% of observations with strongly negative ozone anomalies (∆TCO < −1) led to positive UVI anomalies. Considering only days with strongly positive UVI anomaly (∆UVI > 1), we find (across all sites) that about 90% correspond to negative ∆TCO. The remaining 10% of days occurred during fair weather conditions (SDrel ≥ 80%) explaining the appearance of ∆UVI > 1 despite positive TCO anomalies. Further, we introduce an anomaly amplification factor (AAF), which quantifies the expected change of the ∆UVI for a given change in ∆TCO.

A long term study of the relations between erythemal UV-B irradiance, total ozone column, and aerosol optical depth at central Argentina

Global ultraviolet-B irradiance (UV-B, 280–315nm) measurements made at the campus of the University of Córdoba, Argentina were analyzed to quantify the effects of ozone and aerosols on surface UV-B erythemal irradiance (UVER). The measurements have been carried out with a YES Pyranometer during the period 2000–2013. The effect of ozone and aerosols has been quantified by means of the Radiation Amplification Factor (RAF) and by an aerosol factor (AF, analogous to RAF), respectively. The overall mean RAF under cloudless conditions was (1.2 ± 0.3) %, ranging from 0.67 to 2.10% depending on solar zenith angle (SZA) and on Aerosol Optical Depth (AOD). The RAF increased with the SZA with a clear trend. Similarly, the aerosol effect under almost-constant ozone and SZA showed that, on average, a 1% increase in AOD forced a decrease of (0.15 ± 0.04) % in the UVER, with a range of 0.06 to 0.27 and no defined trend as a function of the SZA. To analyze the effect of absorbing aerosols, an effective single scattering albedo (SSA) was determined by comparing the experimental UVER with calculations carried out with the TUV radiative transfer model.

Temporal Trends in Satellite-Derived Erythemal UVB and Implications for Ambient Sun Exposure Assessment.

Ultraviolet radiation (UVR) has been associated with various health outcomes, including skin cancers, vitamin D insufficiency, and multiple sclerosis. Measurement of UVR has been difficult, traditionally relying on subject recall. We investigated trends in satellite-derived UVB from 1978 to 2014 within the continental United States (US) to inform UVR exposure assessment and determine the potential magnitude of misclassification bias created by ignoring these trends. Monthly UVB data remotely sensed from various NASA satellites were used to investigate changes over time in the United States using linear regression with a harmonic function. Linear regression models for local geographic areas were used to make inferences across the entire study area using a global field significance test. Temporal trends were investigated across all years and separately for each satellite type due to documented differences in UVB estimation. UVB increased from 1978 to 2014 in 48% of local tests. The largest UVB increase was found in Western Nevada (0.145 kJ/m2 per five-year increment), a total 30-year increase of 0.87 kJ/m2. This largest change only represented 17% of total ambient exposure for an average January and 2% of an average July in Western Nevada. The observed trends represent cumulative UVB changes of less than a month, which are not relevant when attempting to estimate human exposure. The observation of small trends should be interpreted with caution due to measurement of satellite parameter inputs (ozone and climatological factors) that may impact derived satellite UVR nearly 20% compared to ground level sources. If the observed trends hold, satellite-derived UVB data may reasonably estimate ambient UVB exposures even for outcomes with long latency phases that predate the satellite record.

Analysis of erythemal UVB and UVA irradiance at Beer Sheva, Israel from 1994 through 2012

The erythemal UVB and UVA irradiance monitored at Beer Sheva, Israel from June 1994 through March 2012 has been analyzed. A statistical analysis was applied to the daily values for each month and average, median, standard deviation, coefficient of variation (%), maximum and minimum values are reported. The maximum and minimum monthly average daily values for both erythemal UVB and UVA occur in June and December, respectively. They are 1.658 Wm−2(ER) and 0.346 Wm−2(ER) for the case of erythemal UVB and the corresponding values for UVA are 300.78 Wm−2 and 135.52 Wm−2. A similar statistical analysis was performed on the monthly average daily values throughout the time interval of this study. In addition, the monthly average daily values were analyzed to determine if there existed any trends for the individual months. A linear regression analysis was applied to the monthly average daily erythemal UVB and UVA irradiance as a function of year. No statistically significant trends were observed, based upon the corresponding p-values; a possible exception being the UVA irradiance during February, which may have a slight negative trend. Typical erythemal UVB and UVA irradiance meteorological years were developed for Beer Sheva and its environs.

The effect of ozone and aerosols on the surface erythemal UV radiation estimated from OMI measurements

Surface erythemal UV radiation is mainly affected by total column ozone, aerosols, clouds, and solar zenith angle. The effect of ozone on the surface UV radiation has been explored many times in the previous studies due to the decrease of ozone layer. In this study, we calculated the effect of aerosols on the surface UV radiation as well as that of ozone using data acquired from Ozone Monitoring Instrument (OMI). First, ozone, aerosol optical depth (AOD), and surface erythemal UVB radiation measured from satellite are compared with those from ground measurements. The results showed that the comparison for ozone was good with r2 of 0.92. For aerosol, there was difference between satellite measurements and surface measurements due to the insufficient information on aerosol in the retrieval algorithm. The r2 for surface erythemal UV radiation was high (∼0.94) but satellite measurements showed about 30% larger values than surface measurements on average by not considering the effect of absorbing aerosols in the retrieval process from satellite measurements. Radiative amplification factor (RAF) is used to access the effect of ozone and aerosol quantitatively. RAF for ozone was 0.97∼1.49 with solar zenith angle. To evaluate the effect of aerosol on the surface UV radiation, only clear-sky pixel data were used and solar zenith angle and total column amount of ozone were fixed. Also, RAF for aerosol was assessed according to the single scattering albedo (SSA) of aerosols. The results showed that RAF for aerosol with smaller SSA ( 0.90). The RAF for aerosol was 0.09∼0.22 for the given conditions which was relatively small compared to that for ozone. However, considering the fact that aerosol optical depth can change largely in time and space while the total column amount of ozone does not change very much, it needs to include the effect of aerosol to predict the variations of surface UV radiation more correctly.

The effect of damaged skin barrier induced by subclinical irritation on the sequential irritant contact dermatitis

Skin damage caused by a single specific stimulus has been extensively studied. However, many additional mild skin irritants are experienced every day before obvious irritant contact dermatitis (ICD) appears. The effect that these previously experienced mild irritations have on the incidence and severity of sequential ICD remains undefined. The purpose of this work was to explore whether the effects of skin barrier damage induced by either the open patch test with 1% sodium lauryl sulfate (SLS), tape stripping test (TAP) (10×), or irradiation with 0.75 median erythemal dose UVB (MED) will affect the severity of sequential irritant dermatitis induced by a 0.5% SLS occlusive patch test (PT).Nine treatments were applied to nine different locations of the ventral forearm of each subject at random. The nine treatment types were as follows: open patch test with 1% SLS; 10× TAP; UVB irradiation with 0.75 MED; open patch test with 1% SLS + PT with 0.5% SLS (SLSPT); 10× TAP + PT with 0.5% SLS (TAPPT); UVB irradiation with 0.75 MED + PT with 0.5% SLS (UVPT); PT with distilled water (DISPT); PT with 0.5% SLS (PT); and the CONTROL (no treatment). After 5 days of subclinical irritation, the PT was applied on day 6. Transepidermal water loss (TEWL), capacitance (CAP), and skin color (a*) were measured at baseline and on days 6, 7, and 8.After the PT, indices of irritancy of PT, UVPT, SLSPT, and TAPPT were 60, 80, 87 and 100%, respectively. The index of irritancy of TAPPT and SLSPT were significantly higher than that of PT (p < 0.05). Clinical scores of SLSPT and TAPPT were also significantly higher than PT (p < 0.05). After 5 days of irritation, TEWL of SLS, TAP, SLSPT, and TAPPT were increased significantly compared to that of baseline. After the PT, D-value of TEWL between day 8 and day 6 (≥6–8TEWL) of SLSPT and TAPPT were greater than that of PT, and D-value of TEWL between day 8 and day 7 (≥7–8TEWL) of SLSPT and TAPPT were less than that of PT values. After the PT, a* values of SLSPT, TAPPT and PT all increased. The D-value of a* between day 8 and day 6 (≥6–8a*) of SLSPT and TAPPT were significantly greater than that of PT. After the PT, D-value of CAP between day 8 and day 6 (≥6–8CAP) of SLSPT was significantly different as compared to PT.The open patch test with 1% SLS and 10× TAP destroys the skin barrier and is able to significantly increase the irritancy and severity of sequential ICD by 0.5% SLS PT, and therefore influences the recovery speed of inflammation. The open patch test with 1% SLS, 10× TAP, and UVB irradiation with 0.75 MED affects the skin barrier to different degrees. TEWL is a sensitive biophysical parameter that can reflect mild damage to the skin barrier induced by subclinical irritation.

Suberythemal ultraviolet B radiation alters the expression of cell cycle-related proteins in the epidermis of human subjects without leading to photoprotection

Deregulation of the cell cycle proteins is one of the critical factors leading to cutaneous carcinogenesis. To monitor the expression of cell cycle proteins in the epidermis of subjects after repeated exposure to ultraviolet (UV) B radiation, and to test for the development of photoprotection by subsequent irradiation with a single erythemal UVB dose. A total of 26 healthy volunteers were divided into four groups: group 1 (n = 9) were given whole-body UVB irradiation for 10 consecutive days with 0.7 minimal erythema dose (MED), group 2 (n = 9) were irradiated as in group 1 followed 24 h later by a single UVB dose of 3 MED on buttock skin, group 3 (n = 4) were irradiated with a UVB dose of 3 MED on buttock skin, and group 4 (n = 4) were not irradiated. Skin biopsies were collected 24 h after the final irradiation and stained for cyclins A, B1, D1, and p16, p18, p21, p27, p53, pRB, Bax and Bcl-2. The expression of cyclin D1, p18 and p21 was significantly higher in groups 1 and 2 compared with the nonirradiated group 4 controls and, in group 2, the expression of pRB, p53 and Bax was also increased. In group 3, only p53 and Bax proteins were significantly elevated compared with group 4. The expression of cyclin D1, p16, p18, p27, pRB and Bcl-2 was higher in group 2 compared with group 3. Suberythemal UVB radiation was sufficient to cause changes in the expression of several epidermal cell cycle proteins. When tested by irradiation with a single erythemal UVB dose following the repeated exposures, no photoprotection against the UV-induced alteration in cell cycle protein expression was apparent.

Reduced IL‐1Ra/IL‐1 ratio in ultraviolet B‐exposed skin of patients with polymorphic light eruption

Polymorphic light eruption (PLE) is a putative delayed-type allergic reaction to (solar) ultraviolet (UV) exposure. Inadequate immune suppression after UVB-induced sunburn appears to be associated with reduced trafficking of Langerhans cells (LCs) out of and neutrophils into the epidermis of patients sensitive to UVB provocation of PLE. Therefore, we investigated whether pro-inflammatory and chemotactic cytokines are differentially expressed in UVB-irradiated skin of UVB-provocable PLE patients (n = 6) and age- and gender-matched healthy controls (n = 6). Interstitial interleukin-1alpha (IL-1alpha), IL-1beta, IL-1Ra, IL-4, IL-8, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein 1-alpha (MIP-1alpha), MIP-1beta and monocyte chemotactic protein-1 (MCP-1) were measured in suction blister fluid raised 16 h after exposure to 0, three and six minimal erythemal UVB doses. In unirradiated skin, the IL-1Ra levels were significantly lower in the PLE patients than in controls (P < 0.05). IL-8 and TNF-alpha levels increased strongly upon UVB irradiation in both groups. No differential shifts in cytokine profiles were found that could explain a reduced trafficking of Langerhans cells and neutrophils in PLE patients. Dose-trend analyses showed that UVB irradiation caused significant increases in IL-1alpha in both groups, and that the levels of IL-1alpha and IL-1beta were on average twofold higher in the PLE group (P = 0.03 and P = 0.004, respectively.). Accordingly, the ratios of IL-1Ra over IL-1alpha and over IL-1beta were overall lower in the skin of PLE patients (P = 0.015 and P < 0.001, respectively.). This shift in cytokines in UVB-irradiated skin of PLE patients reveals an amplified early pro-inflammatory cytokine response, which may contribute to the allergic reaction to UVB radiation.

CD4+ T Cells in Lymph Nodes of UVB-Irradiated Mice Suppress Immune Responses to New Antigens Both In Vitro and In Vivo

The mechanisms by which erythemal UVB irradiation modulates systemic immune responses to antigens applied to non-irradiated sites are poorly understood. In this study, regulatory CD4+ T cells were identified in the skin-draining lymph nodes (SDLNs) of UVB-irradiated, but otherwise naive mice. A transgenic mouse strain (DO11.10) was utilized in which the majority of CD4+ T cells expressed the ovalbumin (OVA(323-339)) T-cell receptor. Thus, T-cell responses could be examined following erythemal UVB irradiation without further antigen sensitization. CD4+ T cells from the SDLNs of UVB-irradiated mice had significantly reduced capacity to respond to presentation of the OVA(323-339) peptide in vitro. Transfer of CD4+ T cells from the SDLNs of UVB-irradiated antigen-naive mice significantly reduced both OVA sensitization and contact hypersensitivity responses to an experimental hapten in the recipient mice. Depletion of CD4+CD25+ cells abrogated this UVB-suppressive effect in the in vitro proliferation assay. There was also a significant increase in the proportion of CD4+CD25+Foxp3+ cells in the SDLNs of UVB-irradiated mice. The potential of these regulatory cells poised to regulate responses to incoming antigens at distant non-irradiated sites broadens the biological impact of UVB irradiation of skin on immunity.

Repeated low-dose ultraviolet (UV) B exposures of humans induce limited photoprotection against the immune effects of erythemal UVB radiation

Exposure of human subjects to ultraviolet (UV) B radiation causes immunosuppression. Most experiments to date have not tested the effects of low daily doses of UVB radiation. To ascertain whether photoprotection against several UV-induced immune effects might develop following repeated exposure. Groups of approximately 30 healthy individuals were given whole-body UVB irradiation on each of 10 consecutive days with 0.7 minimal erythema dose, or whole-body irradiation as before followed by a single erythemal UVB dose on a small body area, or irradiated only with a single erythemal UVB dose on a small body area, or were not irradiated. They were sensitized with diphenylcyclopropenone (DPCP) 24 h after the final dose, and skin biopsies collected to assess cytokine mRNA expression and the number of cells with thymine dimers and expression cyclooxygenase (COX)-1 and COX-2. The contact hypersensitivity (CHS) response to DPCP was significantly lower in the three irradiated groups compared with the unirradiated controls, while cutaneous interleukin (IL)-1beta, IL-6, IL-10 and tumour necrosis factor-alpha mRNAs, COX-1 and COX-2 and thymine dimers were all significantly higher. When the single erythemal UVB dose was given following the repeated low exposures, a slight downregulation in cytokine expression and thymine dimer formation was indicated. The repeated low doses of UVB protected to a limited extent against the effects of an erythemal UVB dose on cytokine expression and thymine dimer formation, but not on CHS or COX enzymes.

Lack of effect of repeated suberythemal ultraviolet‐B exposures on human blood dendritic subtypes

Dendritic cells (DC) play a major role in the afferent immune response. They are found as a minor cell population in the blood as three main subtypes that can be distinguished phenotypically: plasmacytoid DC (PDC), and myeloid DC1 and 2 (MDC1 and 2). The aim of the study was to examine the effect of repeated whole-body suberythemal ultraviolet (UV) B irradiation on the percentages of DC subsets in the blood and skin, and to test for photoadaptation by the subsequent administration of a local erythemal UV dose. Thirty subjects in each group were irradiated with either 0.7 personal minimal erythema dose (MED) UVB daily for 10 days (whole body), or for the 10 days followed by a single three MED UVB exposure of a local body site, or with the single three MED UVB exposure of a local body site only. Blood was collected before and after the exposures and the percentage of DC and DC subtypes assessed by flow cytometry. Skin biopsies were collected at the same times, and the number and position of the DC subsets examined by immunofluorescent microscopy. The whole-body repeated UVB irradiations did not result in a change in the blood DC (BDC) or the subsets percentages in the blood, except that there was a small but significant rise in the percentage of the MDC2 subset. No alteration occurred following the local erythemal UVB exposure. The total number of BDC in the skin was small, with the PDC being located mainly in the dermis and the myeloid subtypes mainly in the epidermis. No change in cutaneous numbers or distribution was revealed following the irradiation protocols. Repeated whole-body suberythemal UVB irradiation does not cause a change in BDC or BDC subsets in the blood or skin, except for a small increase in the percentage of MDC2 in the blood. Local erythemal UVB irradiation does not alter the BDC subsets in blood or skin.

Adaptation of the Human Skin by Chronic Solar-simulating Ultraviolet Irradiation Prevents Ultraviolet-B Irradiation-induced Rise in Serum C-Reactive Protein Levels

Exposure of the skin to UV radiation induces local inflammation. We hypothesized that inflammation induced by erythemal UV-B irradiation could elevate levels of serum C-reactive protein (CRP) and that suberythemal repeating doses of solar-simulating UV radiation (SSR) would produce photoadaptation to such inflammation. Separation-free high-sensitivity assays of CRP show an increase by 42% (P = 0.046) in CRP concentrations in healthy human subjects 24 h after a 3 minimal erythemal dose (MED) dose of UV-B delivered onto a 100 cm2 skin area. Preceding daily suberythemal doses of whole-body SSR for 10 or 30 consecutive days completely prevented the CRP increase. UV-B-induced skin erythema was partially attenuated by 30 preceding days of SSR only (P = 0.00066). After 10 daily SSR doses, the mean baseline CRP concentrations (0.24 +/- 0.21 mg/L) declined by 35% (P = 0.018). Using high-sensitivity analysis of serum CRP as the endpoint marker for cutaneous inflammation, we show that acute exposure of even a relatively small skin area to erythemal UV-B induces skin inflammation detectable also at the systemic level and that photoadaptation by preceding repeating suberythemal doses of SSR reduces signs of inflammation. Our data complement the view given by previous studies in that local photoadaptation also has systemic manifestations.

Single UVB Overexposure Stimulates Melanocyte Proliferation in Murine Skin, in Contrast to Fractionated or UVA-1 Exposure

Overexposure to short- and long-wave ultraviolet radiations (UVB, UVA) may contribute to melanoma development through combined genotoxic and mitogenic effects in melanocytes. This study compares the impact of UVA-1 versus UVB, and single versus fractionated exposures on melanocyte proliferation in hairless SKH-2 mice. A single erythemal dose was compared with an equal dose fractionated over 8 d, and dose-dependency was studied. Proliferation (Ki-67 positive-sign) in melanocytes (melanoma antigen recognized by T-cells-1 positive or micropthalmia transcription factor positive) was ascertained in double-labeled skin sections. Single erythemal UVB exposures caused a delayed, dose-dependent increase of melanocyte proliferation. The highest, 17-fold, increase (from 0.05% to 0.8% of melanocytes) occurred 4 d after UVB exposure, without any detectable effect on overall melanocyte numbers. Correspondingly, DNA repair-deficient xeroderma pigmentosum A (Xpa) mice proved exquisitely sensitive to melanocyte proliferation induction by UVB exposure. No discernable effects were measured from fractionated suberythemal UVB exposures, or from any UVA-1 exposure regimen. Hence, melanocyte proliferation appears to be most efficiently induced by a single UVB overexposure. Moreover, the ineffectiveness of UVA-1 radiation and the enhanced sensitivity of Xpa mice point at pyrimidine dimers as causative DNA lesions. Consequently, murine nevi and melanoma are expected to be most effectively induced by intermittent UVB overexposures.

남극 세종기지에서의 구름 산란에 의한 자외선 변화

For the purpose of understanding the cloud scattering effect of UV radiation at King Sejong station In West Antarctica, we analyzed the data measured by UV-Biometer at surface and compared its result with solar radiation model. The parameterization of UV radiation by cloud ice crystal was applied to solar radiation model and the sensitivity of this model for the variation of ice crystal was tested. The cloud optical thickness was calculated by using this solar radiation model. It was compared the result from calculation with CERES satellite data. In solar radiation model, the UV radiation was less scattered with increase of ice crystal size in cloud and this scattering effect was more important to UV-A radiation than Erythemal UV-B radiation. But scattering effects by altitude of cloud was not serious. The calculated cloud optical thicknesses in Erythemal UV-B and UV-A region were compared with CERES satellite data and the result by UV-A was more accurate than Erythemal UV-B region.

The Angular Distribution of UV-B Sky Radiance under Cloudy Conditions: A Comparison of Measurements and Radiative Transfer Calculations Using a Fractal Cloud Model

Abstract In recent years, global warming concerns have focused attention on cloud radiative forcing and its accurate encapsulation in radiative transfer measurement and modeling programs. At present, this process is constrained by the dynamic movement and inhomogeneity of cloud structure. This study attempts to quantify the UV sky radiance distribution induced by a partial and overcast stratiform cloud field while addressing some of the inherent spatial and temporal errors resulting from cloud. For this purpose, high-quality azimuthally averaged 2-min measurements of erythemal UV-B sky radiance distribution were undertaken by a variable sky-view platform at Hobart, Australia (42.90°S, 147.33°E). Measurements were subsequently compared with Monte Carlo radiative transfer simulations using both a multifractal and plane-parallel homogenous (PPH) cloud field. Data were also compared with several empirical parameterizations. Results at solar zenith angles of 30° and 50° show that for overcast conditions, the multifractal model is superior to the PPH model. For broken cloud conditions, the radiance measurements are biased toward higher instances of direct-beam interruption by cloud. This tends to smooth the near-sun sky radiance field whereas the multifractal model under the same conditions continues to exhibit the circumsolar effect, indicating that its performance may be still valid for radiation modeling. An empirical parameterization of the same multifractal model produced similar sky radiance profiles, warranting its use in radiative transfer models.

대기 복사 모형에 의한 남극 세종기지에서의 복사학적 특징 : 지표면에서 UV-A와 Erythemal UV-B 자외선 양 변화

A solar radiation model was used to investigate the UV radiation at the surface offing Sejong Station in West Antarctica. The results calculated by this model were compared with the values measured by UV-Biometer and UV-A meter during 1999-2000. In this study, the parameterization of solar radiative transfer process was based on Chou and Lee(1996). The total ozone amounts measured by Breve. Ozone Spectrophotometer and the aerosol amounts by Nakajima et al.(1996) was used as the input data of the solar radiative transfer model. And the surface albedo is assumed to be 0.20 in summer and 0.85 in winter. The sensitivity test of solar radiative transfer model was done with the variation of total ozone, aerosol amount, and surface albedo. When the cosine of solar zenith angle is 0.3, Erythemal UV-B radiation decreased 73% with the 200% increase of total ozone from 100 DU to 300 DU, but the decrease of UV-A radiation is about 1%. Also, for the same solar zenith angle, UV-A radiation was decreased 31.0% with the variation of aerosol optical thickness from 0.0 to 0.3 and Erythemal UV-B radiation was decreased only 6.1%. The increase of Erythemal W-B radiation with the variation of surface albedo was twice that of UV-A increase. The surface Erythemal UV-B and UV-A radiation calculated by solar raditive transfer model were compared with the measured values fer the relatively clear day at King Sejong Station in West Antarctica. The model calculated Erythemal UV-B radiation at the surface coincide well with the measured values except for cloudy days. But the difference between the model calculated UV-A radiation and the measured value at the surface was large because of cloud scattering effect. So, the cloud property data is needed to calculate the UV radiation more exactly at King Sejong Station in West Antarctica.

Effects of clouds on the surface erythemal UV-B irradiance at northern midlatitudes: estimation from the observations taken at Belsk, Poland (1999–2001)

Results of 2-year measurements at Belsk, Poland, have been analyzed to investigate the effects of clouds on ultraviolet (UV) radiation. Data were collected using a Solar Light UV-biometer 501A (erythemally weighed UV irradiances), Kipp&Zonnen CM11 pyranometer (total solar radiation), and SCI-TEC Brewer Spectrophotometer (total ozone, aerosol and thin cloud optical depth). Hourly reports on total cloud cover and cloud type were also used in this study. It is found that overcast conditions prevail over central Poland and the sky is covered mainly by low-level clouds. The averaged cloud properties derived from visual observations correspond with those estimated from satellite measurements. An empirical relationship has been postulated for the cloud reduction factor of the erythemally weighted UV radiation as a function of the cloud reduction factor for total solar radiation. The relation may be used to reconstruct the past UV-time series. It is established that information of cloud amount and type to estimate the UV-B attenuation provides a substantial uncertainty. Stronger attenuation of the UV radiation by real clouds was found than that estimated by a radiative transfer model when examining results of the cloud optical depth at 320 nm and the cloud attenuation of the UV radiation measurements. The reduction of the erythemally weighted UV irradiance by thin clouds seems to be independent of the cloud type. It is reported that 1.4% of UV-B irradiance measurements were cloud enhanced in the snowless period of the year. The maximum UV-B enhancement of ∼20% greater than an equivalent clear-sky value was found. Numerous enhancements occurred when high-, mid-, and low- (broken Cu) clouds appeared simultaneously. Similar range of the observed enhancements and cloud composition as in previous cloud enhancement studies (over low latitudinal regions) suggest that common mechanisms may govern this phenomenon in low- and mid-latitudinal regions.