Influence of summer daylight saving time on scattered erythemal solar ultraviolet exposures

The research question of whether there are any influences in the scattered or diffuse erythemal UV exposures to a horizontal plane over a five month period due to the change from standard time to daylight saving time, has been investigated by using physical measurements and applying them to both standard time and daylight saving time. The diffuse erythemal UV was considered for fixed lunch break times and fixed morning and afternoon break times. The cases considered were for groups of the population who are predominantly indoors and who spend their break times outdoors in shade. The biggest influence on the diffuse UV exposures of changing to daylight saving time is the timing of the outdoor meal and break times. The change causes a reduction in diffuse erythemal exposure for early or morning breaks and an increase in the diffuse erythemal exposure for late or afternoon breaks. Similarly, for the lunch break times, the changes in exposure are influenced by the timing of the break with respect to solar noon. Indoor workers who take their breaks outside in a shaded area may have a change in their exposure to diffuse UV due to a shift to daylight saving time, however the magnitude of this change and whether it is a positive or negative change in exposure will depend on the timing of the break. The increase in diffuse UV exposure due to the afternoon break may be negated by the decrease in exposure due to the morning break. In this case, the effect on diffuse UV exposures due to changing to daylight saving time will be minimal.     

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.     

A behavioral model for estimating population exposure to solar ultraviolet radiation

Determining the variability of solar UV exposure of different members of a population by direct measurement demands high compliance over an extended period of time by a large number of people. An alternative approach is to model the variables that affect personal exposure and this is the basis of the method reported here, which uses a random sampling technique to explore variability of exposure at different times of the year by habitués. It is shown that there are large variations in daily personal erythemal exposure, more so for indoor workers living in northern Europe than those resident in Florida, which are due not only to seasonal changes in ambient, but just as importantly to seasonal variation in behavior. Not surprisingly, holiday and summer weekend exposure account for the largest daily UV doses. Northern Europeans who take their summer vacation in Florida can double their exposure during this period compared with holidaying at home and this illustrates just how important sun protection measures should be during recreational exposure in areas of high insolation if the annual UV burden is to be sensibly controlled.     

The objective assessment of lifetime cumulative ultraviolet exposure for determining melanoma risk

Exposure to ultraviolet radiation has commonly been recognized as the most important environmental risk factor for melanoma. The measurement of UV exposure in humans, however, has proved challenging. Despite the general appreciation that an objective metric for individual UV exposure is needed to properly assess melanoma risk, little attention has been given to the issue of accuracy of UV exposure measurement. The present research utilized a GIS based historical UV exposure model (for which the accuracy of exposure estimates is known) and examined, in the case-control setting, the relative importance of UV exposure compared to self-reported time spent outdoors, in melanoma risk. UV estimates were coupled with residential histories of 820 representative melanoma cases among non-Hispanic white residents under 65 years of age from Los Angeles County and for 877 controls matched to cases by age, sex, race, and neighborhood of residence, to calculate the cumulative lifetime UV exposure and average annual UV exposure. For historical measures, when the participants resided outside the US, we also calculated UV estimates. While there was no increased risk of melanoma associated with self-reported time spent outdoors, the association between annual average UV exposure based on residential history and melanoma risk was substantial, as was the association between cumulative UV exposure based on residential history and melanoma. The time spent in outdoor activities appeared to have no significant effect on melanoma risk in any age strata, however, when adjusted for UV exposure based on residential history, time spent outdoors during young age significantly increased risk for melanoma. While there was some attenuation of risk when we excluded data from people resident overseas (as all other studies we are aware of have done), this did not significantly impact subsequent risk estimates of UV exposure on melanoma.     

A numeric model to simulate solar individual ultraviolet exposure

Exposure to solar ultraviolet (UV) light is the main causative factor for skin cancer. UV exposure depends on environmental and individual factors. Individual exposure data remain scarce and development of alternative assessment methods is greatly needed. We developed a model simulating human exposure to solar UV. The model predicts the dose and distribution of UV exposure received on the basis of ground irradiation and morphological data. Standard 3D computer graphics techniques were adapted to develop a rendering engine that estimates the solar exposure of a virtual manikin depicted as a triangle mesh surface. The amount of solar energy received by each triangle was calculated, taking into account reflected, direct and diffuse radiation, and shading from other body parts. Dosimetric measurements (n = 54) were conducted in field conditions using a foam manikin as surrogate for an exposed individual. Dosimetric results were compared to the model predictions. The model predicted exposure to solar UV adequately. The symmetric mean absolute percentage error was 13%. Half of the predictions were within 17% range of the measurements. This model provides a tool to assess outdoor occupational and recreational UV exposures, without necessitating time-consuming individual dosimetry, with numerous potential uses in skin cancer prevention and research.     

The influence of daylight exposure on platelet 5-HT levels in patients with major depression and schizophrenia

Platelet serotonin (5-HT) can be used as a limited, peripheral model for the central 5-HT synaptosomes. Altered platelet 5-HT concentrations have been associated with psychiatric disorders like depression and schizophrenia. The aim of the present study was to compare platelet 5-HT concentrations during long, medium and short period of natural daylight exposure in a large number of medication-free male and female schizophrenic and depressed patients and sex-matched healthy controls. Platelet 5-HT concentration was determined spectrofluorimetrically in 240 (97 female, 143 male) schizophrenic and 258 (153 female, 105 male) nonpsychotic, nonsuicidal depressed medication-free patients and 328 (149 women, 179 men) healthy subjects during periods with short (<12), long (>12) and medium (average 12) hours of the natural daylight. Platelet 5-HT concentration was significantly lower in women compared to men in all groups. Healthy male subjects had significantly higher (p=0.011) platelet 5-HT concentrations during long compared to medium period. There were no significant differences (p>0.05) in platelet 5-HT concentration between different periods in healthy women. The significant increase in platelet 5-HT values were found in female (p=0.01) and male (p=0.029) depressed patients during long compared to short period. There were no significant associations between platelet 5-HT concentrations and different periods in both male and female schizophrenic patients. The results indicate the sex-related differences in the serotonergic system. The alterations of platelet 5-HT concentrations, observed across period with different durations of daylight exposure, point to a direct or indirect effect of light on peripheral 5-HT system that could be related to different sensitivity of the pineal gland to light and/or melatonin influence on 5-HT metabolism.     

Molecular response to ultraviolet radiation exposure in fish embryos: implications for survival and morphological development

UVR exposure is known to cause developmental defects in a variety of organisms including aquatic species but little is known about the underlying molecular mechanisms. In this work we used zebrafish (Danio rerio) embryos as a model system to characterize the UVR effects on fish species. Larval viability was measured for embryos exposed to several UVR spectral treatments by using a solar simulator lamp and an array of UV cutoff filters under controlled conditions in the laboratory. Survival rate and occurrence of development abnormalities, mainly caudal (posterior) notochord bending/torsion, were seriously affected in UV-exposed larvae reaching values of 53% and 72%, respectively, compared with non-UV-exposed larvae after 6 days postfertilization (dpf). In order to elucidate the molecular mechanisms involved, a matricellular glycoprotein named osteonectin and the expression of a DNA-repair related gene, p53, were studied in relation to UVR exposure. The results indicate that osteonectin and p53 expression were increased under UVR exposure due to wavelengths shorter than 335 nm (i.e. mainly UVB) and 350 nm (i.e. short UVA and UVB), respectively. Furthermore, parallel experiments with microinjections of osteonectin-capped RNA showed that malformations induced by osteonectin overexpression were similar to those observed after a UVR exposure. Consequently this study shows a potential role of osteonectin in morphological deformities induced by solar UV radiation in zebrafish embryos.     

Measurement of ultraviolet exposure in epidemiological studies of skin and skin cancers

As our understanding of the role of UV in causing skin cancer continues to expand, researchers and clinicians must continue to remain up to date on the various means by which UV exposure can be quantified. The purpose of this article was to review the current methods used to measure lifetime exposure to UV and to summarize the strengths and weaknesses of each of these approaches. Thus we include here a review of research articles that deal with questionnaire reliability and physical examination. We also review more technologically advanced techniques used to measure chronic UV exposure; these include microtopography, histology, gene studies and spectroscopy. Both the utility of using a specific measurement technique and the accuracy of particular techniques are explored. Finally, we touch upon the results of articles that link UV exposure to skin cancer and what this means for the future of UV-induced skin cancer research.     

Neutrophil infiltration in normal human skin after exposure to different ultraviolet radiation sources

Exposure of the skin to UV radiation can lead to a local infiltration of neutrophils. Not much is known on whether the infiltration of neutrophils in the irradiated skin is UV source dependent. In this study we compared different UV sources (solar-simulated radiation [SSR], narrowband [NB]-UVB, broadband [BB]-UVB and UVA1) in their potency to induce neutrophil infiltration in normal human skin after exposure to two times the minimal erythema dose of UV radiation. Biopsies were collected from irradiated buttock skin 6 and 24 h after irradiation and from nonirradiated skin. The presence, distribution and amount of skin-infiltrated neutrophils were determined using immunohistochemical staining. Analysis revealed that SSR was most effective in inducing neutrophil infiltration. NB-UVB gave a neutrophil influx pattern similar to that seen with SSR but in smaller numbers. BB-UVB and UVA1 were far less potent in inducing neutrophil infiltration compared with SSR or NB-UVB. Our findings indicate that neutrophil infiltration in the UV-irradiated skin is UV source dependent. When the spectra emitted by the different UV sources were compared UVB seemed to be more effective than UVA in inducing neutrophil infiltration. Furthermore, our results suggest that longer wavelengths within the UVB range are mostly responsible for the infiltration of neutrophils in the UV-irradiated skin.     

Correlations between reported and measured ultraviolet radiation exposure of mothers and young children

Cumulative and intermittent sun exposure are risk factors for skin cancer, highlighting the need to monitor exposure during childhood. There is currently very little available information concerning the accuracy of self-reported levels of sun exposure, particularly for very young children. In this study, UV radiation (UVR) exposure measured by polysulfone dosimeters worn on the wrist was compared with a measure of estimated exposure using a diary based on recall at the end of the 4 day study period and ambient dosimetric measures. Results of the study indicate that the relative UVR exposures expressed as a fraction of daily total ambient received during the 4 day period by young children and mothers are similar. A high level of association was obtained for the estimated levels of exposure between young children and their mothers. Moderate correlations were evident for dosimeter readings of mother and child on weekends with no significant association on weekdays. The association between estimated exposure and dosimeter readings was poor and needs improvement. This may be achieved by greater consideration of structural and environmental factors that influence the levels of UVR exposure received by individuals and by increasing the level of specificity in the measurement instruments. Methodological issues such as recall of exposure after several days, quantity of sun exposure and more precise measurement of grades of exposure when outside may have more impact than previously expected, and further information is being sought with a larger sample for exposure during the summer months.     

Solvents for ultraviolet spectrophotometry

Mathematical relations are presented showing the effect of light absorption by the solvent on the absorption measurements. A simple modification in the silica-gel adsorption method of purifying isooctane is described that greatly improves the transmittance in the 2000 Å region. A procedure of purifying dioxan is also included.     

Optimization of the conditions for biuret complex formation for the determination of peptides by capillary electrophoresis with ultraviolet detection

Capillary electrophoresis with UV detection was utilized to optimize copper complexation conditions for the analysis of neuropeptides. Complexation was confirmed by monitoring the response at a visible wavelength. Four complexation strategies were used to compare the UV response of native peptides and their respective copper complexes. All four strategies resulted in complete complexation, but on-capillary complexation provided significant advantages over precapillary and pre-/on-capillary. An increase in UV absorbance along with peak stacking resulted in a significantly greater response using the on-capillary technique. Also, on-capillary complexation does not require dilution of the sample. The effects of temperature and copper concentration were also investigated. The utility of this method for the separation of an enkephalin peptide mixture is presented.     

Youth solar ultraviolet radiation exposure, concurrent activities and sun-protective practices: a review

To assist standardization of procedures, facilitate comparisons, and help guide research efforts to optimally inform development of appropriately targeted interventions, there is a need to review methods used to quantify child and adolescent solar ultraviolet radiation (UV) exposure, related outdoor activities and sun-protective practices. This holistic approach is essential for comprehensive research that will provide all-inclusive, informative and meaningful messages for preventive measures of harmful UV exposure. Two databases were searched and 29 studies were retrieved, and these studies report measurement or assessment techniques documenting UV exposure patterns and related outdoor activities. Polysulfone film badges were the main measurement instrument used in 10 studies, with questionnaire, survey data, observation, a model, electronic dosimeters, biological dosimeters, colorimeter and UV colouring labels used in the remaining studies. Methods used to record activities included self-report, parental report, a logbook and observation. Measurement duration and unit of UV exposure varied in most studies, but a method common to 15 studies was measured UV exposure as a percentage of ambient UV. The studies reviewed do not provide sufficient information for the development and evaluation of targeted youth sun protection programs. Studies are required which document precise UV exposure, concurrent activities and sun protection usage for children and adolescents.     

Chemical alteration of poly(tetrafluoroethylene) Teflon induced by exposure to vacuum ultraviolet radiation and comparison with exposure to hyperthermal atomic oxygen

The chemical alteration of poly(tetrafluoroethylene) Teflon by vacuum ultraviolet radiation (VUV) (115–400 nm) has been examined with X‐ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.98 decreases to 1.65 after a 2‐h exposure. The F/C atom ratio is further reduced to a steady‐state value of 1.60 after a 74‐h exposure. The high‐resolution XPS C1s data indicate that new chemical states of carbon form as F is removed and that the relative amounts of these states depend on the F content of the near‐surface region. The states are most likely due to C bonded only to one F atom, C bonded only to other C atoms, and C that has lost a pair of electrons through the emission of F^?. The exposure of the VUV‐damaged surface to research‐grade O₂ results in the chemisorption of a very small amount of O, and this indicates that large quantities of reactive sites are not formed during the chemical erosion by VUV. Further exposure to VUV removes this chemisorbed oxygen. A comparison of the XPS data indicates that the mechanisms of chemical alteration by VUV radiation and hyperthermal (～5 eV) atomic oxygen are different, as expected, because the excitation sources are quite different. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 552–561, 2005     

Standard loading controls are not reliable for Western blot quantification across brain development or in pathological conditions

A frequently utilized method of data quantification in Western blot analysis is comparison of the protein of interest with a house keeping gene or control protein. Commonly used proteins include β‐actin, glyceraldehyde 3 phosphate dehydrogenase (GAPDH), and α‐tubulin. Various reliability issues have been raised when using this technique for data analysis—particularly when investigating protein expression changes during development and in disease states. In this study, we have demonstrated that β‐actin, GAPDH, and α‐tubulin are not appropriate controls in the study of development and hypoxic‐ischemic induced damage in the piglet brain. We have also shown that using an in‐house pooled standard, loaded on all blots is a reliable method for controlling interassay variability and data normalization in protein expression analysis.     

Diurnal variation of ocular exposure to solar ultraviolet radiation based on data from a manikin head

Measurements were conducted at San Ya, China (18.4°N, 109.7°E, altitude 18 m) to investigate the diurnal variation of ocular exposure to ultraviolet (UV) radiation. The experimental apparatus was composed of a manikin and a dual-detector spectrometer to simultaneously measure ocular and ambient UV data. The experimental apparatus was rotated clockwise to simulate three different types of exposure. When the manikin was facing into the sun, the ocular exposure to UV radiation on a summer day was bimodally distributed. The maximum ocular UV irradiance occurred at solar elevations of around 40° and 50° for UVA and UVB respectively. The spectral irradiances were measured at specific wavelength to obtain the ocular biologically effective UV (UV(BE) ) irradiances for photokeratitis, photoconjunctivitis and cataract, and the UV index (UVI) was calculated at the same time point for comparison. When the manikin faced the sun, the maximal ocular UV(BE) irradiance values were obtained at the solar elevation where the UVI value was 8. The results of this study showed that protection against ocular overexposure during outdoor activities should be taken not only at noon but also at other times.     

Effects of ultraviolet B exposure on the expression of proliferating cell nuclear antigen in murine skin

Proliferating cell nuclear antigen (PCNA) is an active nuclear protein involved in DNA replication, recombination and repair. PCNA is found throughout the basal layer in normal skin and in all layers of the epidermis in malignancy. This study evaluates PCNA's expression after acute and chronic UV-B irradiation. Skh-1 hairless mice exposed to 1.5 and 4.5 kJ/m2 of UV-B were sacrificed at 6, 12, 24, 48, 72 and 168 h. Immunohistochemical analysis revealed PCNA expression throughout the basal layer of untreated skin, with diminished expression at 6 h, indicative of immediate UV damage, and evidenced by the observable upregulation in pyrimidine dimer formation early on. Subsequently, PCNA immunoreactivity progressively increased, demonstrating an aberrant upward epidermal migratory pattern in association with chronic exposure. The 4.5 kJ/m2 group exhibited prolonged recovery in staining and also demonstrated this altered migratory pattern with chronic exposure. Progressive reactivation of PCNA expression occurs with repair. PCNA migration to upper layers of the epidermis indicates proliferation and possibly a subsequent increased malignant potential. We conclude that PCNA can serve as a marker of DNA repair and indirectly as an indicator of UV-B-induced damage, expression being time dependent and dose related. Specific immunoreactivity patterns and the observable atypia in keratinocytes are relevant in elucidating malignant potentiation.     

Transparent perfluoropolyethers for vacuum ultraviolet applications

After a broad scouting based on quantum chemical calculations, optical absorption measurements in the vacuum ultraviolet (VUV) wavelength region between 140 and 190 nm were performed on a narrower series of commercial and experimental liquids. By elimination of sources of external contamination, mainly due to atmospheric gases, the analysis of the contributions to the absorption related to the backbone structure and to the chain end composition allowed the synthesis of a novel family of linear perfluoropolyethers (PFPEs) with optical absorbance at 157 nm between 0.3 and 0.6 cm(-1) in a broad range of compositions and molecular weights. The dependence of the optical threshold on the PFPE composition demonstrates that -OCF2- is the most transparent segmental unit in the VUV region.     

Photoacclimation to long-term ultraviolet radiation exposure of natural sub-Antarctic phytoplankton communities: Fixed surface incubations versus mixed mesocosms

Solar UVB radiation (280-320 nm) is known to have detrimental effects on marine phytoplankton. Associated with the seasonal ozone hole in Antarctica, stratospheric ozone depletion occasionally influences the sub-Antarctic (Beagle Channel, Argentina) region, enhancing levels of UVB. The primary objective of this work was to study the effects of several (i.e. 6-10) days of exposure to UVB on the taxonomic composition and photosynthetic inhibition of local phytoplankton communities. For different light treatments, fixed-depth incubations placed in an outdoors water tank were compared with incubations in 1900 L mesocosms, where vertical mixing was present. Phytoplankton growth was inhibited by UV radiation (UVR) in fixed-depth experiments but not in the mixed mesocosms. Under fixed and mixed conditions alike, photosynthesis was significantly inhibited by UVB at the beginning of the experiment but no longer after several days of exposure, suggesting that cells had acclimated to radiation conditions. There was a change in species composition in response to UVR exposure in both experiments, which likely explained acclimation. In the community exposed to fixed conditions this change was from a phytoflagellate-dominated assemblage to a community with high relative abundance of diatoms after 6 days of exposure. UVA was responsible for most of the observed growth inhibition; however, the reduction in photosynthesis was produced by UVB. The reasons behind this variability in responses to UVR are associated with species-specific sensitivity and acclimation, and the previous light history of cells. In the community exposed in mesocosms, an assemblage codominated by phytoflagellates and diatoms was observed at the beginning of the experiments. After 10 days of exposure, green algae (Eutreptiella sp.) had increased, and phytoflagellates were the dominant group. The synthesis of mycosporine-like amino acids (MAAs), antioxidant enzymes and photosynthetic antenna pigments, in relation to repair and protection processes, may explain the reduced inhibition of both growth and photosynthesis that was observed in the phytoplankton community after several days of exposure. For environments such as the Beagle Channel seasonally exposed to the ozone hole, the results obtained from the fixed-depth experiments show that species can cope with UVR by means of MAA synthesis, while mixing would primarily promote a change in species composition and defense strategies.     

Sun protecting and sun exposing behaviors: testing their relationship simultaneously with indicators of ultraviolet exposure among adolescents

The aim of this study was to build on existing understanding of adolescent sun-related behavior by combining sun protecting and sun exposing behaviors and testing their relationship simultaneously with indicators of ultraviolet (UV) exposure. Data were collected for 692 adolescents aged between 12 and 18 years. General linear modeling was undertaken to test the relationship of sun-related behaviors with indicators of UV exposure. Overall, the combined sun protection and sun exposing behaviors accounted for 13.8% of the variance in the number of sunburns, 28.1% of the variance in current tan and 57.5% of the variance in desired tan, respectively. Results indicated that having a strong desire for a tan was significantly associated with spending time tanning, delaying the use of sun protection, wearing brief clothing and using no sun protection; whereas the number of sunburns was significantly associated with sunscreen use, avoiding peak hours and delaying sun protection. Current tan was significantly associated with wearing sunglasses, shade use and time spent tanning. In examining sun-related behaviors among adolescents, consideration needs to be given to both sun exposing and sun protecting behaviors. This research has important implications for conceptualizing outcomes in programs designed to reduce UV exposure.