Ambient Solar UV Research Articles

Linkages between COVID-19, solar UV radiation, and the Montreal Protocol

There are several connections between coronavirus disease 2019 (COVID-19), solar UV radiation, and the Montreal Protocol. Exposure to ambient solar UV radiation inactivates SARS-CoV-2, the virus responsible for COVID-19. An action spectrum describing the wavelength dependence of the inactivation of SARS-CoV-2 by UV and visible radiation has recently been published. In contrast to action spectra that have been assumed in the past for estimating the effect of UV radiation on SARS-CoV-2, the new action spectrum has a large sensitivity in the UV-A (315–400 nm) range. If this “UV-A tail” is correct, solar UV radiation could be much more efficient in inactivating the virus responsible for COVID-19 than previously thought. Furthermore, the sensitivity of inactivation rates to the total column ozone would be reduced because ozone absorbs only a small amount of UV-A radiation. Using solar simulators, the times for inactivating SARS-CoV-2 have been determined by several groups; however, many measurements are affected by poorly defined experimental setups. The most reliable data suggest that 90% of viral particles embedded in saliva are inactivated within ~ 7 min by solar radiation for a solar zenith angle (SZA) of 16.5° and within ~ 13 min for a SZA of 63.4°. Slightly longer inactivation times were found for aerosolised virus particles. These times can become considerably longer during cloudy conditions or if virus particles are shielded from solar radiation. Many publications have provided evidence of an inverse relationship between ambient solar UV radiation and the incidence or severity of COVID-19, but the reasons for these negative correlations have not been unambiguously identified and could also be explained by confounders, such as ambient temperature, humidity, visible radiation, daylength, temporal changes in risk and disease management, and the proximity of people to other people. Meta-analyses of observational studies indicate inverse associations between serum 25-hydroxy vitamin D (25(OH)D) concentration and the risk of SARS-CoV-2 positivity or severity of COVID-19, although the quality of these studies is largely low. Mendelian randomisation studies have not found statistically significant evidence of a causal effect of 25(OH)D concentration on COVID-19 susceptibility or severity, but a potential link between vitamin D status and disease severity cannot be excluded as some randomised trials suggest that vitamin D supplementation is beneficial for people admitted to a hospital. Several studies indicate significant positive associations between air pollution and COVID-19 incidence and fatality rates. Conversely, well-established cohort studies indicate no association between long-term exposure to air pollution and infection with SARS-CoV-2. By limiting increases in UV radiation, the Montreal Protocol has also suppressed the inactivation rates of pathogens exposed to UV radiation. However, there is insufficient evidence to conclude that the expected larger inactivation rates without the Montreal Protocol would have had tangible consequences on the progress of the COVID-19 pandemic.Graphical abstract

High Ambient Solar UV Correlates with Greater Beta HPV Seropositivity in New South Wales, Australia.

Human papillomavirus (HPV) infection is highly prevalent worldwide and may have a role, with sun exposure, in causing cutaneous squamous cell carcinoma. Little is known about the relationship of UV exposure and seroprevalence of cutaneous HPVs in the general population. Using multiplex serology, we estimated the seroprevalence of 23 beta and 7 gamma HPVs and 7 other antigens (mu HPV1, HPV63, nu HPV41, alpha HPV16; polyomaviruses HPyV7 and MCV; p53) in a population-based sample of 1,161 Australian 45 and Up Study participants with valid data from blood specimens collected from 2010 to 2012. We calculated prevalence ratios (PR) for the association of each antigen with residential ambient solar UV and other UV-related variables. Seropositivity for at least one beta or gamma HPV was high at 88% (beta HPVs 74%, gamma HPVs 70%), and less in women than men [e.g., PR beta-2 HPV38 = 0.70; 95% confidence interval (CI), 0.56-0.87; any gamma = 0.90; 95% CI, 0.84-0.97]. A high ambient UV level in the 10 years before study enrollment was associated with elevated seroprevalence for genus beta (PRtertile3vs1 any beta = 1.17; 95% CI, 1.07-1.28), and beta-1 to beta-3 species, but not for gamma HPVs. Other UV-related measures had less or no evidence of an association. Seroprevalence of cutaneous beta HPVs is higher with higher ambient UV exposure in the past 10 years. The observed association between ambient UV in the past 10 years and cutaneous HPVs supports further study of the possible joint role of solar UV and HPV in causing skin cancer.

Effect of increased UV-B radiation on biological control of the gray mold by Clonostachys rosea and on the expression of strawberry defense-related enzymes

Changes in UV-B radiation can have large effects on the management of the pathogen Botrytis cinerea, especially on strawberry production in Brazil. The aim of this work was to investigate the effect of the increased UV-B radiation on biological control of gray mold by Clonostachys rosea and on the expression of plant defense-related enzymes. The experiments were laid out in randomized complete blocks in a split-plot design. The whole-plot factor was represented by UV-B treatments: 1. ambient solar UV; 2. ambient solar UV reduced by 80% (UV-); 3 ambient solar UV supplemented with UV-B lamps (UV+). The split-plot factors were: 1. plants sprayed with water (control); 2. plants exposed to B. cinerea; 3 plants sprayed weekly with an inoculum suspension of C. rosea and exposed to B. cinerea. The latent infection of B. cinerea was evaluated during five weeks per season, after which leaves were collected to assess the peroxidase, polyphenoloxidase and chitinase activities. No significant effect on B. cinerea incidence for irradiation treatments were observed during both seasons, although C. rosea treatments have been able to control gray mold on fruits. The enzymatic activity was related to the ambient condition, not to the exposure of the plants to these micro-organisms. Only UV+ conditions led to an increase of polyphenoloxidase activity in season 2. The results indicate that the increase of UV-B radiation has no influence on the ability of C. rosae to control the gray mold on strawberry.

Effects of ambient solar UV radiation on grapevine leaf physiology and berry phenolic composition along one entire season under Mediterranean field conditions

In the present study we assessed the effects of ambient solar UV exclusion on leaf physiology, and leaf and berry skin phenolic composition, of a major grapevine cultivar (Tempranillo) grown under typically Mediterranean field conditions over an entire season. In general, the effects of time were stronger than those of UV radiation. Ambient UV caused a little stressing effect (eustress) on leaf physiology, with decreasing net photosynthesis rates and stomatal conductances. However, it was not accompanied by alterations in Fv/Fm or photosynthetic pigments, and was partially counterbalanced by the UV-induced accumulation of protective flavonols. Consequently, Tempranillo leaves are notably adapted to current UV levels. The responses of berry skin phenolic compounds were diverse, moderate, and mostly transitory. At harvest, the clearest response in UV-exposed berries was again flavonol accumulation, together with a decrease in the flavonol hydroxylation level. Contrarily, responses of anthocyanins, flavanols, stilbenes and hydroxycinnamic derivatives were much more subtle or nonexistent. Kaempferols were the only compounds whose leaf and berry skin contents were correlated, which suggests a mostly different regulation of phenolic metabolism for each organ. Interestingly, the dose of biologically effective UV radiation (UVBE) was correlated with the leaf and berry skin contents of quercetins and kaempferols; relationships were linear except for the exponential relationship between UVBE dose and berry skin kaempferols. This opens management possibilities to modify kaempferol and quercetin contents in grapevine through UV manipulation.

Synchrotron X-ray phase contrast imaging of leaf venation in soybean (Glycine max) after exclusion of solar UV (280-400 nm) radiation.

The hydraulic efficiency of a leaf depends on its vascular structure as this is responsible for transport activities. To investigate the effect of exclusion of UVAB and UVB radiation from the solar spectrum on the micro-structure of leaves of soybean (Glycine max, variety JS-335), a field experiment was conducted using synchrotron-based phase contrast imaging (PCI). Plants were grown in specially designed UV exclusion chambers, and wrapped with filters that excluded UVB (280-315 nm) or UVAB (280-400 nm), or transmitted all the ambient solar UV (280-400 nm) radiation (filter control). Qualitative observation of high-resolution X-ray PCI images obtained at 10 keV has shown the differences in major and minor vein structures of the leaves. The mid-rib width of the middle leaflet of third trifoliate leaves, for all treatments, were obtained using quantitative image analysis. The width of the mid-rib of the middle leaflet of third trifoliate leaves of UVB excluded plants was found to be more compared to leaves of filter control plants, which are exposed to ambient UV. The mid-rib or the main conducting vein transports water and sugars to the whole plant; therefore, mid-rib enhancement by the exclusion of solar UV radiation possibly implies enhancement in the leaf area which in turn causes an increased rate of photosynthesis.

Vitamin D response of older people in residential aged care to sunlight-derived ultraviolet radiation.

The aim of this study was to determine the vitamin D response to sunlight ultraviolet radiation in older people. Increases in vitamin D depended on the season of exposure, but the changes were small. Natural sun exposure is not a practical intervention for vitamin D deficiency in this population. The purpose of this study is to measure the ultraviolet radiation (UVR) exposure of those in residential aged care in an earlier trial of sunlight exposure and to determine its effect on their vitamin D response. Attendance data, demographic, clinical and biochemical variables for 248 participants were used for a secondary analysis of a previous cluster randomized trial of sunlight exposure and falls. The ambient solar UV Index data were used to calculate the participants' UVR dose. Multiple linear regression was used to test if UVR exposure over 6 months, as measured by the standard erythemal dose (SED), was a predictor of vitamin D response, controlling for age, gender, BMI, calcium intake, baseline vitamin D and season of exposure. The median 25-hydroxyvitamin D (25OHD) was 32.4 nmol/L at baseline and 34.6 nmol/L at 6 months (p = 0.35). The significant predictors of 25OHD at 6 months were UVR exposures in spring-summer (coefficient = 0.105, 95 % confidence interval (CI) 0.001-0.209, p = 0.05) and autumn-winter (coefficient = 0.056, 95 % CI 0.005-0.107, p = 0.03) and baseline vitamin D (adjusted coefficient = 0.594, 95 % CI 0.465-0.724, p = 0.00). In those starting sunlight sessions in spring, an increase of 1 unit in log SED was associated with 11 % increase in 25OHD. Natural UVR exposure can increase 25OHD levels in older people in residential care, but depends on the season of exposure. However, due to inadequate sun exposure, 25OHD did not reach optimal levels. Nevertheless, where sun exposure is encouraged in this group, the focus for the start of exposure should be in the months of spring or autumn, as this timing was associated with a vitamin D response.

The relationship between solar UV exposure, serum vitamin D levels and serum prostate-specific antigen levels, in men from New South Wales, Australia: the CHAMP study

We aim to determine the relationship between season, personal solar UV exposure, serum 25(OH)D and 1,25(OH)2D and serum prostate-specific antigen (PSA) levels. Questionnaire data and blood samples were collected at baseline from participants of the Concord Health and Ageing in Men Project (n = 1,705), aged 70 and above. They were grouped as men 'free of prostate disease' for those with no record of having prostate cancer, benign prostatic hyperplasia, or prostatitis and with serum PSA levels below 20 ng/mL, and 'with prostate disease' for those with a record of either of these diseases or with serum PSA levels 20 ng/mL or above. Personal solar UV exposure (sUV) was estimated from recalled hours of outdoor exposure and weighted against ambient solar UV radiation. Sera were analysed to determine levels of PSA, 25(OH)D and 1,25(OH)2D, and analysed using multiple regression, adjusting for age, BMI and region of birth. The association between sUV and serum PSA levels was conditional upon season (p interaction = 0.04). There was no direct association between serum PSA and 25(OH)D in both groups of men. There was a positive association between serum PSA and 1,25(OH)2D in men with prostate disease (mean = 110.6 pmol/L; p heterogeneity = 0.03), but there was no such association in men free of prostate disease (mean = 109.3 pmol/L; p heterogeneity = 0.8). The association between PSA and sUV may only be evident at low solar UV irradiance, and this effect may be independent of serum vitamin D levels.

Intraspecific variations in growth, yield and photosynthesis of sorghum varieties to ambient UV (280–400 nm) radiation

A field study was conducted to investigate the impact of ambient solar UV on the various growth, physiological and yield parameters of four sorghum (Sorghum bicolor L.) varieties—Indore-12, Indore-26, CSV-23 and Indore-27 by excluding either UV-B (<315nm) or UV-A/B (<400nm) components of solar spectrum. Exclusion of UV significantly enhanced plant height, area and specific leaf weight of flag leaf, biomass accumulation, yield parameters and harvest index in all the sorghum varieties. Chlorophyll b was significantly enhanced and chlorophyll a increased to a lesser extent, UV-B absorbing substances and chlorophyll a/b ratio were significantly decreased by the exclusion of solar UV. The enhancement in the vegetative growth and yield by UV exclusion might be linked to the remarkable increase in rate of photosynthesis in sorghum varieties. The magnitude of the response was high in I-26 and I-27 as compared to CSV-23 and I-12 after exclusion of solar UV. All the varieties of sorghum had a negative cumulative stress response index (CSRI), the sensitivity of the sorghum varieties was in the following sequence I-12>CSV-23>I-26>I-27. Thus I-27 was the most sensitive and I-12 the least sensitive variety to present level of solar UV radiation. The differences in UV sensitivity identified among sorghum varieties might be useful in breeding programs for increased tolerance to UV-B radiation.

Abstract 5482: Sun exposure and prostate cancer risk in New South Wales, Australia: A case control study

Abstract Background Ultraviolet-B radiation in sunlight may influence risk of developing prostate cancer. Method We examined the relationship between individual solar UV exposure and risk for prostate cancer in a case control study combining the New South Wales (Australia) Prostate Cancer Care and Outcome (cases) and Non-Hodgkin Lymphoma (controls) studies. Results There was evidence that increasing solar UV exposure increased prostate cancer risk (adjusted OR for highest vs. lowest quartiles of average weekly, warmer months sun exposure 2.07 95% CI: 1.36-3.16) and that this increased risk was most evident with weekend sun exposure (adjusted OR 5.54 95%CI: 2.94-10.43). Increased sun sensitivity was also associated with increased risk of prostate cancer (adjusted OR 1.63 95% CI: 1.09-2.44 for very high sun sensitivity). Conclusion Our results suggest that increasing solar UV exposure increases prostate cancer risk in a high ambient solar UV environment. Impact Given that previous studies conducted mainly in low solar UV environments found either no evidence of an association or evidence of a negative association; our findings suggest the possibility of a U-shaped dose effect relationship between exposure to solar UV and prostate cancer. Further studies are needed to test the hypothesis that high solar UV exposure is a risk factor for prostate cancer and to explore possible mechanisms for such an association. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5482. doi:1538-7445.AM2012-5482

Continuous-flow solar UVB disinfection reactor for drinking water

Access to safe, reliable sources of drinking water is a long-standing problem among people in developing countries. Sustainable solutions to these problems often involve point-of-use or community-scale water treatment systems that rely on locally-available resources and expertise. This philosophy was used in the development of a continuous-flow, solar UVB disinfection system. Numerical modeling of solar UVB spectral irradiance was used to define temporal variations in spectral irradiance at several geographically-distinct locations. The results of these simulations indicated that a solar UVB system would benefit from incorporation of a device to amplify ambient UVB fluence rate. A compound parabolic collector (CPC) was selected for this purpose. Design of the CPC was based on numerical simulations that accounted for the shape of the collector and reflectance. Based on these simulations, a prototype CPC was constructed using materials that would be available and inexpensive in many developing countries. A UVB-transparent pipe was positioned in the focal area of the CPC; water was pumped through the pipe to allow exposure of waterborne microbes to germicidal solar UVB radiation. The system was demonstrated to be effective for inactivation of Escherichia coli, and DNA-weighted UV dose was shown to govern reactor performance. The design of the reactor is expected to scale linearly, and improvements in process performance (relative to results from the prototype) can be expected by use of larger CPC geometry, inclusion of better reflective materials, and application in areas with greater ambient solar UV spectral irradiance than the location of the prototype tests. The system is expected to have application for water treatment among communities in (developing) countries in near-equatorial and tropical locations. It may also have application for disaster relief or military field operations, as well as in water treatment in areas of developed countries that receive relatively intense solar UVB radiation.

Effect of Exclusion of Ambient Solar Uv-A/B Components on Growth and Antioxidant Response of Cotton (Gossypium Hirsutum L.)

The influence of ambient solar UV-A or UV-B radiation on growth responses was investigated in three varieties of cotton (Gossypium hirsutum L.) after exclusion of solar UV-A/B radiation: JK-35, IH-63 and Khandwa-2. Cotton plants were grown from seeds in UV-exclusion chambers lined with selective UV filters to exclude either UV-B (280–315 nm) or UV-A/B (280–400 nm) from the solar spectrum under field conditions. Excluding UV-B and UV-A/B significantly increased plant height, leaf area and dry weight accumulation in all three varieties of cotton. The varieties differed considerably in their sensitivity to ambient UV-A/B. Khandwa-2 was most sensitive and JK-35 least sensitive to ambient solar UV. We monitored the activity of the antioxidant enzymes superoxide dismutase (SOD), ascorbic acid peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (GPX), as well as the level of the antioxidant ascorbic acid (ASA), in primary leaves of the most UV-sensitive variety (Khandwa-2). The level of UV-B-absorbing substances was significantly decreased by exclusion of solar UV-B and UV-A/B. Exclusion of solar UV decreased the activity of all the antioxidant enzymes monitored and the level of ascorbic acid versus control plants (+UV-A/B) grown under filters transparent to solar UV. Reduction of the antioxidant defense after UV exclusion indicates that ambient solar UV exerts significant stress and induces some reactive oxygen species to accumulate, which in turn retards the growth and development of cotton plants. Ambient solar UV stresses cotton plants, shifting their metabolism towards defense against solar UV. Exclusion of solar UV eliminates the need for that defense and leads to enhancement of primary metabolism.

Photosynthesis and yield in cotton (Gossypium hirsutum L.) Var. Vikram after exclusion of ambient solar UV-B/A

The impact of ambient solar UV was studied on the photosynthesis and yield of cotton (Gossypium hirsutum) var. Vikram in a field experiment by excluding either UV-B (<315 nm) or UV-B/A (<400 nm) components of solar spectrum. Cotton plants were grown in cages covered with polyester filters that could specifically cut off UV-B or UV-B/A part of the solar spectrum. The control plants were grown under a filter transmissible to UV. Exclusion of UV enhanced plant height, leaf area, total biomass, and the yield parameters (number and weight of bolls, length of fiber and number of seeds) of cotton. Enhancement in the vegetative growth and yield of the plants could be related to enhanced rate of photosynthesis in the leaves. Polyphasic chlorophyll a fluorescence (OJIP) transients from UV excluded plants gave a higher fluorescence yield at I–P phase. Fluorescence measurements indicated enhanced F v/F m ratio and reduction capacity after exclusion of solar UV. Exclusion also enhanced stomatal conductance and intercellular CO2 concentration and reduced the stomatal resistance. Total soluble proteins were higher after UV exclusion, and in SDS–PAGE analysis, bands corresponding to smaller subunits (14 kDa) of Rubisco were more intensely stained. Experiments indicated suppressive action of ambient UV on carbon fixation and yield of cotton plants. Exclusion of solar UV proved to be beneficial in enhancing the yield of cotton plants.

Temporal changes in effects of ambient UV radiation on natural communities of Antarctic marine protists

The effects of ambient solar UV radiation (280 to 400 nm) were determined using 3 nat- ural marine protist communities incubated in 650 l tanks (minicosms) for 13 to 14 d over the summer of 2002-2003 at Davis Station, Antarctica. Minicosms were exposed to ambient light that was vari- ously attenuated to give treatments of photosynthetically active radiation (PAR, ≥385 nm wave- length), PAR + UV-A radiation (315 to 385 nm), and PAR + UV-A + 4 different treatments of UV-B radiation (280 to 315 nm) that simulated a range of equivalent depths (ED) in the water column from 4.43 to 7.15 m. Results showed a seasonal progression in the response of microbial communities to UV radiation exposure. The first experiment in November showed that the microbial community was sig- nificantly inhibited in the PAR + UV-A-exposed treatment but this inhibition declined with increas- ing addition of UV-B radiation. The second experiment in December showed that UV-A or UV-B radi- ation had few significant effects. Like in Expt 1, some taxa were inhibited by PAR + UV-A or promoted by UV-B, but most were inhibited at the highest UV-B irradiances (≤4.43 m ED). The last experiment in January showed UV-B induced inhibition of all but one of the dominant taxa. The sea- sonal transition in UV wavelengths responsible for inhibition of protists may be due to ozone reduc- tion, the light history of protists, and/or changes in species composition. The increasing UV-B- induced inhibition we observed over the summer corresponded to a decline in ozone concentrations over Davis. This recurrent decline in ozone over Antarctica between January and April coincides with blooms of diatoms that appear to have low UV-B tolerance but are responsible for ~47% of annual primary production in Antarctic waters.

Ambient Solar UV Radiation Causes Mortality in Larvae of Three Species of Rana Under Controlled Exposure Conditions†¶

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290–320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens,Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290–380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species tested are more sensitive than the embryonic stages. This suggests that previous reports that have not included the larval life stage may underestimate the risk posed to some anuran populations by increasing UV-B exposure. Furthermore, this study reports quantitative UV-B dosimetry data, collected in conjunction with the exposures, which can be used to begin the assessment of the impact of environmental changes which increase UV-B exposure of these anurans.

Number of Nevi and Early-Life Ambient UV Exposure Are Associated with BRAF-Mutant Melanoma

Malignant melanomas often contain BRAF or NRAS mutations, but the relationship of these mutations to ambient UV exposure in combination with phenotypic characteristics is unknown. In a population-based case series from North Carolina, 214 first primary invasive melanoma patients in the year 2000 were interviewed regarding their risk factors. Ambient solar UV exposures were estimated using residential histories and a satellite-based model. Cases were grouped on the basis of BRAF and NRAS somatic mutations, determined using single-strand conformation polymorphism analysis and radiolabeled DNA sequencing, and the risk profiles of these groups were compared. Mutually exclusive BRAF-mutant and NRAS-mutant cases occurred at frequencies of 43.0% and 13.6% with mean ages at diagnosis of 47.3 and 62.1 years, respectively. Tumors from patients with >14 back nevi were more likely to harbor either a BRAF mutation [age-adjusted odds ratio (OR), 3.2; 95% confidence interval (95% CI), 1.4-7.0] or an NRAS mutation (age-adjusted OR, 1.7; 95% CI, 0.6-4.8) compared with patients with 0 to 4 back nevi. However, BRAF-mutant and NRAS-mutant tumors were distinctive in that BRAF-mutant tumors were characteristic of patients with high early-life ambient UV exposure (adjusted OR, 2.6; 95% CI, 1.2-5.3). When ambient UV irradiance was analyzed by decadal age, high exposure at ages 0 to 20 years was associated with BRAF-mutant cases, whereas high exposure at ages 50 and 60 years was characteristic of NRAS-mutant cases. Our results suggest that although nevus propensity is important for the occurrence of both BRAF and NRAS-mutant melanomas, ambient UV irradiance influences risk differently based on the age of exposure. The association of BRAF mutations with early-life UV exposure provides evidence in support of childhood sun protection for melanoma prevention.

Content of total phenolics and phenolic acids in tomato ( Lycopersicon esculentum Mill.) fruits as influenced by cultivar and solar UV radiation

Two cultivars of fresh market tomato [Oregon Spring (OS) and Red Sun (RS)] were each grown in two high tunnels at Beltsville, MD covered with a contrasting material of similar thickness (0.152 mm) and durability (4-year polyethylene). One covering material (Tyco Tufflite IV) transmitted ambient solar UV radiation from 290 to 400 nm (designated+UV) while the other material (Dura-Film Super 4) blocked UV wavelengths below 380 nm (designated−UV). Both films transmitted comparable amounts of photosynthetically active radiation (PAR) from 400 to 700 nm. Ripe tomato fruits comparable in size and development were collected at maturity from plants of the two cultivars grown in each high tunnel under the contrasting covering materials. Four lots of tomatoes of each cultivar and each UV treatment were assayed for total phenolic (TP) content by a colorimetric Folin-Ciocalteu (FC) assay and for content of individual phenolic acids by a high performance liquid chromatography (HPLC)-diode array detection (DAD) procedure. The phenolic acids extracted from the base hydrolyzed fraction were identified as caffeic acid, p-coumaric acid, and ferulic acid. Caffeic acid was the predominant phenolic acid in both tomato cultivars (OS and RS) grown in the two high tunnels. The total concentration of these three phenolic acids measured by HPLC was approximately 20% higher under +UV than under −UV treatment; this was true for both cultivars. A similar trend in quantities of TP yield was also observed when tomato extracts were assayed by a FC method. These results indicate that the phenolic content of tomato fruits is significantly affected by the spectral quality of solar UV radiation. Since phenolic compounds are known to play a key role as antioxidants in human nutrition, subtle differences in phenolic composition between the two high tunnels as a result of differences in the UV transmission properties of these different covering materials may be of considerable importance.

Ultraviolet Radiation at Places of Residence and the Development of Melanocytic Nevi in Children (Australia)

To investigate the relationship between ambient ultraviolet radiation (UV) exposure and number of melanocytic nevi in children. A longitudinal study of nevi was conducted in 1614 children in Perth, Australia. Children had nevi counted on the back, face and arms at ages 6, 10, and 12 years. Erythemally effective UV irradiance was used to estimate ambient exposure from their places of residence before entry to the study at age 6 years. Data on UV radiation were derived from satellite measurements of ozone and atmospheric reflectivity. At baseline, the response rate was 70%. At age 10, 90% of those recruited had nevus counts and at age 12, 69%. Children who had migrated to Perth from geographical locations with higher erythemal irradiance had, on average, 1.34 (95% confidence interval, 1.16-1.54) times as many nevi on the back at age 6, 1.29 (1.13-1.49) as many at age 10 and 1.10 (0.92-1.30) times as many at age 12. No significant associations were seen for the face or arms. Ambient solar UV exposure in early childhood is positively associated with number of nevi and nevi develop soon after exposure to sunlight.

Modelled effects of ambient UV radiation on a natural Antarctic marine microbial community

Ozone depletion over Antarctica has enhanced ultraviolet-B radiation (UVBR, 280 to 320 nm wavelength). We measured the effect of ambient solar UV radiation on the biomass and species composition of phytoplankton, protozoa, bacteria and dissolved organic carbon (DOC) in natural microbial assemblages from Antarctic coastal waters. Results were modelled to determine the features of the irradiance responsible for changes in the biomass of these microbial components and responses of individual phytoplankton taxa. Model results showed that changes in phytoplankton biomass were primarily due to dose rate, indicating that their UV-induced mortality resulted from the equilibrium between damage and repair. However, there was considerable variability between individual species in their response to dose and dose rate. Changes in protozoan biomass were mainly due to dose and were likely due to community-level, trophodynamic interactions. UV radiation did not measurably affect bacterial biomass, but resulted in increasing concentrations of DOC. We found a threshold of erythemal irradiance of 28 mW m-2, approximating peak noon-time irradiance at 3.6 m depth near the summer solstice in Antarctic coastal waters, below which no change in the community structure was observed, but above which phytoplankton mortality and protozoan biomass increased. Our results indicate that enhanced UVB radiation in Antarctic waters increases phytoplankton mortality and causes changes in the structure, function and composition of the microbial community that are likely to return more photoassimilated carbon to the atmosphere. © Inter-Research 2006.

Impacts of ambient solar uv (280-400 nm) radiation on three tropical legumes

Tropical regions receive the highest level of global solar ultraviolet (UV) radiation especially UV-B (280-320 nm). The average daily dose of the UV-B radiation in Madurai, South India (10°N) is 10 kJ m-2. This is approximately 50% more than the average daily UV-B radiation in many European countries. A field study was conducted using selective filters to remove either the UV-B (< 320 nm) or UV-B/A (<400 nm) of the solar spectrum, and the effects were followed inCyamopsis tetragonoloba, Vigna mungo, andVigna radiata to determine their sensitivity to UV. When compared to ambient radiation, exclusion of solar UV-B increased the seedling height, leaf area, fresh weight and dry weight and the crop yield by 50% in the case ofCyamopsis, and the extent of such increase was slightly less under UV-B/A exclusion. InV. mungo a significant reduction was seen in solar UV excluded plants whileV. radiata was found to be unaffected.

Spectral Properties of Selected UV‐blocking and UV‐transmitting Covering Materials with Application for Production of High‐value Crops in High Tunnels†

The spectral properties of selected UV-blocking and UV-transmitting covering materials were characterized by means of a UV-VIS spectroradiometer or a UV-VIS spectrometer to provide researchers and growers with guidelines for selecting suitable materials for use in studying the effects of ambient solar UV radiation on the production of tomatoes and other high-value crops in high tunnels. A survey was made of a wide range of plastic covering materials to identify commercially available products that had the desired characteristics of transmitting high levels of photosynthetically active radiation and of being stable under ambient solar UV radiation. The study was focused on evaluating films that either blocked or transmitted UV wavelengths below 380 nm to determine comparative growth, yield and market quality and to provide a tool for integrated pest management. Based on this survey, two contrasting covering materials of similar thickness (0.152 mm) and durability (4-year polyethylene), one a UV-blocking film and the other a UV-transmitting film, were selected and used to cover two high tunnels at Beltsville, MD. Spectroradiometric measurements were made to determine comparative spectral irradiance in these two high tunnels covered with these materials and under ambient solar UV radiation. Comparative measurements were also made of selected glass and plastic materials that have been used in UV exclusion studies.