Effective Ultraviolet Radiation Research Articles

Red and green fluorescent carbon dots for highly effective ultraviolet radiation screening and sensing

Carbon dots (CDs) have attracted intense attention because of their excellent optical properties, low toxicity, and biocompatibility. CDs have a great potential to be used as fluorescent sensors and ultraviolet (UV)-blocking materials. In this research, CDs were synthesized by the hydrothermal method using mangosteen leaves as a precursor. A CD aqueous solution exhibited bright green (G-CDs) and red (R-CDs) fluorescence with naked-eye observation under UV irradiation. The maximum fluorescence emission peak intensities of G-CDs and R-CDs were observed at 312 nm and 671 nm under excitation wavelengths of 275 nm and 410 nm, respectively. The absorbance spectra of CDs are shown in the UV range of 200–400 nm. The transmission spectra indicate that the G-CD solution screens UVB and UVC, while R-CDs are an excellent block for all UVA, UVB, and UVC. The average UV-shielding efficiencies of R-CDs and G-CDs are 97.4 %, and 56.1%, respectively. Furthermore, the R-CDs have a tendency to screen high-energy blue light. FTIR results display functional groups of organic substance on CD surfaces showing that the CDs have good biocompatibility with organics and biological materials. Moreover, nanocomposite films of CDs and polyvinyl alcohol (PVA) polymer (CDs/PVA) were prepared using a drop-casting method. In the polymerized state, R-CDs/PVA and G-CDs/PVA exhibit significant improvements in average UV ray blockage of 100.0%, and 83.8% enhancement, respectively. It is noteworthy that PVA combined with R-CDs achieves complete UV ray blocking. Furthermore, the emissions from both CD solution and CDs/PVA under UV radiation cover the regions of red, green, and blue emission. Hence, this work demonstrates the performance of R-CDs- and G-CDs-based platforms that show a high potential for UV-shielding and sensing applications.

Genotoxic risk assessment of solar UV radiation in tadpoles from Brazilian wetlands

Solar ultraviolet (UV) radiation is an environmental genotoxic factor linked to amphibian decline. Here we assessed the genotoxic risk of UVB and UVA exposure for tadpoles from open ponds in southern Brazil, a mid-latitude region influenced by stratospheric ozone depletion. Daily UV doses were measured on the surface of a pond in Taim Ecological Station (TAIM; 32°49’24’’S; 52°38’31’’W) on a cloudless summer day to predict the worst-case scenario for UV-induced DNA damage. Pond descriptors were related to the use of microhabitats by Boana pulchella tadpoles in two ponds over the climate seasons of 2013 and 2014. Our results indicate that shaded microhabitats were more frequent than unshaded ones in autumn, winter, and spring but not in summer. Hence, the penetration of UV radiation into the water of unshaded microhabitats was evaluated through laboratory experiments with artificial UV sources and pond water samples. Physical and biological sensors were applied in the experiments to measure the incident UV radiation and its genotoxic action. By integrating field and laboratory data, we demonstrate that low doses of biologically effective UV radiation reached the tadpoles in autumn, winter, spring, and early summer due to a high proportion of shaded microhabitats and a high concentration of solids in unshaded microhabitats. However, the relative reduction of shaded microhabitats jointly with a declining water level in late summer may have exposed tadpoles to high UV doses. Our experiments also indicate that solar UVB radiation, but not UVA, is primarily responsible for the induction of DNA pyrimidine dimers in organisms living under the surface of aquatic ecosystems. The present work highlights the determinant role of wetland descriptors for minimizing the genotoxic potential of UV radiation and its consequences for amphibians.

Bearing Extremes: Impacts from Simulated Outer Space Conditions and Effective Ultraviolet Radiation Shielding Materials on Tardigrade Life History.

Questions about astrobiological resilience, whether entities with evolutionary histories on Earth would survive in outer space or on distant planets, for instance, no longer reside exclusively in the science fiction realm. In this study, we assess life history characteristics for individuals in the tardigrade species Grevenius annulatus post exposure to simulated outer space conditions with nonionizing radiation as a proxy for anticipated oxidative stress and damage incurred from exposure to full-spectrum environmental radiation. Using a planetary environment simulator, we exposed unshielded and shielded specimens to UVB and UVC radiation for 30 min and monitored and recorded subsequent life history characteristics. Survivorship was lower in an unshielded group relative to control as well as Kevlar and polyethylene shielded groups, demonstrating that Kevlar and polyethylene reduce impact from these types of nonionizing radiation, which are not expected to fully penetrate the shields. Cumulative egg production was lowest in the unshielded group, but egg viability and average egg production rate was highest. Due to insignificant differences, additional research to determine the relative effectiveness for Kevlar and polyethylene as shielding materials from survivorship and reproduction perspectives is warranted. This work provides a progressive step from which important conditions excluded in the current study, like vibrations, temperatures, debris-impacts, and ionizing radiation, can be included in future studies.

Persistent extreme ultraviolet irradiance in Antarctica despite the ozone recovery onset

Attributable to the Montreal Protocol, the most successful environmental treaty ever, human-made ozone-depleting substances are declining and the stratospheric Antarctic ozone layer is recovering. However, the Antarctic ozone hole continues to occur every year, with the severity of ozone loss strongly modulated by meteorological conditions. In late November and early December 2020, we measured at the northern tip of the Antarctic Peninsula the highest ultraviolet (UV) irradiances recorded in the Antarctic continent in more than two decades. On Dec. 2nd, the noon-time UV index on King George Island peaked at 14.3, very close to the largest UV index ever recorded in the continent. On Dec. 3rd, the erythemal daily dose at the same site was among the highest on Earth, only comparable to those recorded at high altitude sites in the Atacama Desert, near the Tropic of Capricorn. Here we show that, despite the Antarctic ozone recovery observed in early spring, the conditions that favor these extreme surface UV events persist in late spring, when the biologically effective UV radiation is more consequential. These conditions include long-lasting ozone holes (attributable to the polar vortex dynamics) that often bring ozone-depleted air over the Antarctic Peninsula in late spring. The fact that these conditions have been occurring at about the same frequency during the last two decades explains the persistence of extreme surface UV events in Antarctica.

Broadband reflection in polymer-stabilized cholesteric liquid crystal film with zinc oxide nanoparticles film thermal diffusion method

ABSTRACT Broadband reflective films were prepared by thermal diffusion of zinc oxide nanoparticles (ZnO NPs) in chiral nematic liquid crystals (N*-LCs). Ultraviolet (UV) light was irradiated in the direction of the thickness of the liquid crystal film to form the intensity gradient of UV light, to induce the gradient distribution of the pitch. The effects of the content of ZnO NPs, the UV light intensity, the UV irradiation time, the monomer concentration, and the diffusion temperature on the reflective bandwidth of the sample were studied. The results show that the appropriate content of ZnO NPs and the effective UV radiation intensity is beneficial to the broadband reflection of the sample. To elucidate the mechanism of photoinduced pitch gradients, the fracture surface of the sample film was observed by scanning electron microscopy (SEM), and the influence of experimental conditions on the broadband reflection performance of N*-LCs films was analysed theoretically.

Does solar ultraviolet radiation play a role in COVID-19 infection and deaths? An environmental ecological study in Italy

A significantly stronger impact in mortality and morbidity by COVID-19 has been observed in the northern Italian regions compared to the southern ones. The reasons of this geographical pattern might involve several concurrent factors. The main objective of this work is to investigate whether any correlations exist between the spatial distribution of COVID-19 cases and deaths in the different Italian regions and the amount of solar ultraviolet (UV) radiation at the Earth's surface. To this purpose, in this environmental ecological study a mixed-effect exponential regression was built to explain the incidence of COVID-19 based on the environmental conditions, and demographic and pathophysiologic factors. Observations and estimates of the cumulative solar UV exposure have been included to quantify the amount of radiation available e.g., for pre-vitamin D3 synthesis or SARS-CoV-2 inactivation by sunlight. The analysis shows a significant correlation (p-value <5 × 10−2) between the response variables (death percentage, incidence of infections and positive tests) and biologically effective solar UV radiation, residents in nursing homes per inhabitant (NHR), air temperature, death percentage due to the most frequent comorbidities. Among all factors, the amount of solar UV radiation is the variable contributing the most to the observed correlation, explaining up to 83.2% of the variance of the COVID-19 affected cases per population. While the statistical outcomes of the study do not directly entail a specific cause-effect relationship, our results are consistent with the hypothesis that solar UV radiation impacted on the development of the infection and on its complications, e.g. through the effect of vitamin D on the immune system or virus inactivation by sunlight. The analytical framework used in this study, based on commonly available data, can be easily replicated in other countries and geographical domains to identify possible correlations between exposure to solar UV radiation and the spread of the pandemic.

Pupils' use of school outdoor play settings across seasons and its relation to sun exposure and physical activity.

Long outdoor stay may cause hazardous exposure to ultraviolet radiation (UVR) from the sun even at high latitudes as in Sweden (Spring to Autumn). On the other hand, long outdoor stay is a strong predictor of primary school children´s free mobility involving moderate to vigorous physical activity (MVPA). UV-protective outdoor environments enable long outdoor stay. We investigated the concurrent impact of different school outdoor play settings upon pupils´ sun exposure and levels of physical activity across different ages, genders, and seasons. During 1week each in September, March, and May, UVR exposure and MVPA were measured in pupils aged 7-11years. Erythemally effective UVR exposure was measured by polysulphone film dosimeters and MVPA by accelerometers. Schoolyard play was recorded on maps, and used areas defined as four play settings (fixed play equipment, paved surfaces, sport fields, and green settings), categorized by season and gender. During the academic year, sport fields yielded the highest UVR exposures and generated most time in MVPA. In March, time outdoors and minutes in MVPA dropped and UVR exposures were suberythemal at all play settings. In May, green settings and fixed play equipment close to greenery promoted MVPA and protected from solar overexposure during long outdoor stays. More outdoor activities in early spring are recommended. In May, greenery attractive for play could protect against overexposure to UVR and stimulate both girls and boys to vigorous play.

Method for Measurements of Terrestrial Ultraviolet Radiation on Inclined Surfaces in Personal Dosimetry Field Studies.

Understanding personal ultraviolet radiation (UVR) exposure is essential for the evaluation of the health risks and benefits; however, personal dosimetry could be challenging in large-scale or/and long-term population studies. Alternatively, personal exposure could be simulated using three-dimensional models and lifestyle surveys together with data on a body position with respect to the sun. These models require a real-time input on local environmental UVR. The main challenge in using this method is retrieval of the diffuse irradiance as it requires an often-expensive tracking of solar position. In this study, a hypothesis that UVR measured on a vertical plane in the north direction can be used in the UK as a proxy for diffuse radiation was tested against direct measurements and compared with models based on solar tracker data in Chilton, UK, (51.57°N) in June-July 2018. The statistical analysis over 17 days under all weather conditions showed that for 45° and 90° tilted surfaces the proposed method performed as well as the best of the models based on solar tracker data. A proposed system could offer a portable and low-cost alternative to measurements of diffuse radiation by solar tracking radiometers for spatial distribution of terrestrial erythema effective UVR in population field studies.

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.

The Janus face of iron on anoxic worlds: iron oxides are both protective and destructive to life on the early Earth and present-day Mars.

The surface of the early Earth was probably subjected to a higher flux of ultraviolet (UV) radiation than today. UV radiation is known to severely damage DNA and other key molecules of life. Using a liquid culture and a rock analogue system, we investigated the interplay of protective and deleterious effects of iron oxides under UV radiation on the viability of the model organism, Bacillus subtilis. In the presence of hydrogen peroxide, there exists a fine balance between iron oxide's protective effects against this radiation and its deleterious effects caused by Photo-Fenton reactions. The maximum damage was caused by a concentration of hematite of ∼1 mg/mL. Concentrations above this confer increasing protection by physical blockage of the UV radiation, concentrations below this cause less effective UV radiation blockage, but also a correspondingly less effective Photo-Fenton reaction, providing an overall advantage. These results show that on anoxic worlds, surface habitability under a high UV flux leaves life precariously poised between the beneficial and deleterious effects of iron oxides. These results have relevance to the Archean Earth, but also the habitability of the Martian surface, where high levels of UV radiation in combination with iron oxides and hydrogen peroxide can be found.

Solar ultraviolet doses and vitamin D in a northern mid-latitude

Solar ultraviolet (UV) radiation is one of the most important factors in the development of skin cancer in human, solar erythema and skin aging. Nevertheless, numerous studies have shown the benefits of UV solar radiation in moderate doses, such as the reduction of blood pressure and mental health, treatment of various diseases, and the synthesis of vitamin D in the skin.This paper analyses data from solar ultraviolet erythemal (UVER) irradiance in W/m2 measured in a northern mid-latitude as Valencia (Spain) for the period 2003–2010. To estimate effective solar UV radiation in the production of vitamin D (UVD) we used the relationship proposed by McKenzie et al. (2009). It was obtained for one month for each season the minimum exposure time needed around solar noon and at 9 UTC and 15 UTC (Coordinated Universal Time) to obtain the recommended daily dose of 1000IU. Also, it has been calculated time for erythema induction around solar noon for the same months.The median UVER daily dose during the summer months was 4000J/m2day, and 700J/m2day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m2day, and in winter it was 1000J/m2day.Around noon in January it takes more than two hours of solar exposure to obtain the recommended daily dose of vitamin D, whereas the rest of the year range between 7min on July and 31min on October. For the same months around noon, exposure times to produce erythema were obtained, these being of higher value to the previous.The results show that it is difficult to obtain the recommended vitamin D doses in winter in a northern mid-latitude, as the human body is almost entirely covered in this season.

Action spectra affect variability of the climatology of biologically effective ultraviolet radiation on cloud-free days

Action spectrum (AS) describes the relative effectiveness of ultraviolet (UV) radiation in producing biological effects and allows spectral UV irradiance to be weighted in order to compute biologically effective UV radiation (UVBE). The aim of this research was to study the seasonal and latitudinal distribution over Europe of daily UVBE doses responsible for various biological effects on humans and plants. Clear sky UV radiation spectra were computed at 30-min time intervals for the first day of each month of the year for Rome, Potsdam and Trondheim using a radiative transfer model fed with climatological data. Spectral data were weighted using AS for erythema, vitamin D synthesis, cataract and photokeratitis for humans, while the generalised plant damage and the plant damage AS were used for plants. The daily UVBE doses for the above-mentioned biological processes were computed and are analysed in this study. The patterns of variation due to season (for each location) and latitude (for each date) resulted as being specific for each adopted AS. The biological implications of these results are briefly discussed highlighting the importance of a specific UVBE climatology for each biological process.

A sun holiday is a sunburn holiday

Many people take holidays in sunny locations with the express aim of sunbathing. This may result in sunburn, which is a risk factor for skin cancer. We investigated 25 Danish sun seekers during a week's holiday in the Canary Islands. The percentage of body surface area with sunburn was determined by daily skin examinations by the same observer. Erythemally effective ultraviolet radiation (UVR) exposure was assessed with time-stamped personal dosimeters worn on the wrist. Volunteers reported their clothing cover and sunscreen use in diaries, and this information was used to determine body site-specific UVR doses after adjustment for sun protection factor. Remarkably, we found that all volunteers sunburned at some point. The risk of sunburn correlated significantly with the adjusted body site-specific UVR dose. Furthermore, there was also a significant relationship between the daily UVR dose and percentage of body surface area with sunburn. Our study shows that holiday UVR exposure results in a high risk of sunburn, which potentially increases the risk of skin cancer. Possible protection by melanogenesis is insufficient to protect against sunburn during a 1-week sun holiday. Finally, our data clearly support a substantial skin cancer risk from sun holidays.

Projected changes in clear-sky erythemal and vitamin D effective UV doses for Europe over the period 2006 to 2100

The benefits and the harmful effects of solar ultraviolet radiation (UVR) exposure have been well discussed. Most studies show concern for the solar overexposure in the tropics and low latitude sites and its scarcity at higher latitudes. Both cases are of concern, the first for diseases such as skin cancer and the second for the lack of vitamin D production in the skin. In this study, we evaluate the influence of climate change scenarios on the total ozone content (TOC) and typical aerosol properties, such as the optical depth (AOD) and single scattering albedo (SSA), over Europe. From these parameters, we estimate the erythemal and the vitamin D effective UVR doses from 2006 to 2100. Our results indicate a small reduction of the UVR daily doses caused by the ozone layer recovery and partially compensated by an AOD diminution through this century. The attenuation will be larger at high latitudes, during the springtime and for more polluted scenarios during this century. However, this diminution should not be sufficient to provide a protection condition for erythema. On the other hand, at higher latitudes, it possibly contributes to a relevant increase in the exposure time necessary for the synthesis of vitamin D, mainly during autumn and spring seasons.

Effects of ultraviolet radiation on the growth, reproduction and survival of the lobate ctenophore Mnemiopsis leidyi in Chesapeake Bay

Solar ultraviolet radiation (UVR) is an environmental stressor that can have a variety of negative effects on aquatic organisms including slowed growth, changes in reproduction and increased mortality. The ctenophore Mnemiopsis leidyi is a highly transparent organism that has not been shown to actively avoid ultraviolet radiation or possess photoprotective compounds and may therefore be vulnerable to deleterious effects of UVR. Results of this study indicate that summertime UVR exposure equivalent to average UVR conditions within the top 0.5m of the water column of the Rhode River, Maryland, USA, can cause mortality and reduced size of M. leidyi. Exposures tested did not, however, affect egg production beyond that attributable to UVR effects on mortality. Experiments indicated a sharp threshold for the tolerance of M. leidyi to biologically effective UVR exposure. A biological weighting function (BWF) was experimentally determined to describe the spectral dependence of UV induced mortality. The BWF was similar to those previously reported for mesozooplankton. M. leidyi is an important component of many ecosystems; thus, changes in its population size and abundance have the potential to significantly affect coastal and estuarine food webs, and oyster, fish and sea nettle populations, in systems like Chesapeake Bay. Future scenarios of decreased eutrophication and runoff that result in reduced dissolved organic matter and particulates, will likely lead to increased amounts and penetration of UVR in coastal and estuarine systems and could increase deleterious effects of UVR on M. leidyi.

Solar UV exposure in construction workers in Valencia, Spain

Exposure to ultraviolet radiation (UVR) has long been recognized as the most important environmental risk factor for melanoma and skin cancer. Outdoor workers are among the groups most at risk from exposure to solar UVR in their daily activities. Sensitive spore-film filter-type personal dosimeters (VioSpor) were used to measure the biologically effective UVR received by construction workers in the course of their daily work. The study took place in Valencia, Spain, in July 2010 and involved a group of eight workers for a period of 5 days. The median UV exposure was 6.11 standard erythema dose (SED) per day, with 1 SED defined as effective 100 J/m(2) when weighted with the Commission Internationale de L'Eeclairage erythemal response function. These workers were found to receive a median of 13.9% of total daily ambient ultraviolet erythemal radiation (UVER). Comparison with the occupational UVR exposure limit showed that the subjects had received UVER exposure in excess of occupational guidelines, indicating that protective measures against this risk are highly advisable.

Method of estimating solar UV radiation in high-latitude locations based on satellite ozone retrieval with an improved algorithm

The effects of the cloudiness and satellite-based ozone measurements on erythemally effective ultraviolet (EUV) radiation were examined using a non-linear regression model. Instead of the widely used ozone transmissivity exponential function, we proposed a new approach based on a quantum transmission model using hyperbolic attenuation of the EUV radiation. The radiation data were collected at the Czech Johann Gregor Mendel Station, James Ross Island, Antarctica (63° 48′ S, 57° 53′ W), between 14 March 2007 and 3 March 2009. The total ozone content and effective surface reflectivity at 360 nm were obtained from the Ozone Monitoring Instrument on board the EOS-Aura spacecraft for the geographical coordinates of the J. G. Mendel Station. The model predicted 98.6% variability of the EUV radiation. The residuals between the measured and predicted EUV radiation intensities were evaluated separately for the ranges of solar elevation angle, total ozone content and surface reflectivity. The results of this study were compared to previous findings where the influence of ground-based and satellite-based ozone measurements and model usefulness was discussed.

Solar UV exposure of primary schoolchildren in Valencia, Spain

To quantify schoolchildren's exposure to ultraviolet erythemal radiation (UVER), personal dosimeters (VioSpor) were used to measure biologically effective ultraviolet (UV) radiation received in the course of their daily school activities. The study took place in two primary schools in Valencia (39°28'N), Spain, for several weeks from March 2008 until May 2009, with two age groups (6-8 years and 10-11 years) and involved about 47 schoolchildren. The median daily UV exposure values for all age groups and solar height intervals considered in the study ranged from 1.31 to 2.11 standard erythemal doses (SEDs). Individual UV exposure was analyzed as a function of age, gender and dosimeter position. Significant statistical differences were found between different age groups, with the younger age group receiving higher statistically significant UVER exposure. It was also found that boys received significantly higher UVER exposure than girls. It was also noted that shoulder dosimeters registered higher readings than wrist dosimeters. Exposure ratio (ER) is defined as the ratio between the personal dose on a selected anatomical site and the corresponding ambient dose on a horizontal plane. The median ER for all age groups and solar height intervals in the study range from 4.5% to 10.7%, with higher values at lower solar heights.

Solar ultraviolet radiation incident upon reef snorkelers determined by consideration of the partial immersion of dosimeters in the natural ocean environment

Reef snorkelling is potentially a high-risk activity for persons visiting tropical and sub-tropical waters due to possible overexposure to solar ultraviolet radiation (UVR). Measurements and modelled estimates of the UVR received by human subjects are presented for a 10° latitudinal gradient of Australia's Great Barrier Reef and some Melanesian Islands (15°S to 25°S). A technique is described to measure the erythemally effective UVR received by the neck and the lower back. Measurements were made by application of a hybrid in-air and submerged calibration for polysulphone dosimeters. Measured exposures were used to model UVR exposure distributions at a number of popular snorkelling sites. A total of 11 snorkelling trials were held between 29 September 2009 and 26 January 2010. Exposures measured to the back and expressed relative to the horizontal plane ambient UVR have shown there to be some variation in the UVR distribution, with the neck receiving the greatest proportion of ambient UVR (0.56 ± 0.14 (1σ)), followed by the lower back (0.36 ± 0.14 (1σ)). Similarly high UVR exposures were determined at neck and lower back sites for different seasons, different times of day and over the latitudinal range of the study.

Estimation of solar UV radiation in maritime Antarctica using a nonlinear model including cloud effects

A new approach to the estimation of erythemally effective ultraviolet (EUV) radiation for all sky conditions that occur in maritime Antarctica is reported. The spatial variability of the total ozone content (TOC) and attenuation of the EUV radiation in the atmosphere are taken into consideration. The proposed nonlinear regression model of EUV radiation is described by a hyperbolic transmission function. The first results and the model validation for Vernadsky Station (formerly the British Faraday Station) during the period 2002–2005 show very good agreement with the measured values (R 2 = 99.2). The developed model was evaluated using daily doses of EUV radiation with respect to solar elevation angle and cloudiness. The mean average prediction error (MAPE) for cloudy (4.1–7.0 oktas) and overcast skies (7.1–8.0 oktas) varied between 4.0% and 4.3%, while for partly cloudy days (0–4.0 oktas) with high variability of cloud types during a day, MAPE reached 5.9%.