The European Light Dosimeter Network: four years of measurements

The European Light Dosimeter Network (ELDONET) has now been functional for more than four years. The network is based on dosimeters which measure radiation in three biologically relevant wavelength bands (UV-B, 280-315 nm; UV-A, 315-400 nm; and Photosynthetic Active Radiation, PAR, 400-700 nm). The ELDONET network is currently based on 33 stations with 40 instruments. The distribution of the instruments all over Europe allows measurement of the latitudinal and longitudinal light climate distribution. In addition, several instruments are active in South America, New Zealand, India, Africa and Japan. With some exceptions, the measured yearly doses depend on the latitude. While the maximal daily doses are almost comparable from station to station, seasonal changes and the different maximal solar zenith angles account for the differences in total yearly doses. Ratioing between UV-B and PAR allows the detection of subtle changes in the local light climate, due, for example, to mini-ozone holes encountered in northern Europe during spring. Comparison of satellite ozone data with terrestrial ELDONET measurements revealed an overall weak correlation between these data sets. However, local weather conditions, solar zenith angle and latitude as well as reflectivity (i.e. clouds and aerosol; satellite data) show a much stronger correlation to the doses received. The close relationship between the spectral sensitivity of the UV-B sensor used in the ELDONET dosimeter and the CIE erythemal action spectrum allows determination of the erythemal dose on the basis of the dosimeter readings.     

All-Weather Comparison between Spectral and Broadband (Robertson-Berger) UV Measurements

Abstract— Spectral measurements of UV irradiance at the Fraunhofer Institute at Garmisch-Partenkirchen, Germany, are intercompared with data from two different Robert-son-Berger-type meters. More than 21000 spectra gathered during 20 months of continuous operation were used for this analysis, sampling a large variety of atmospheric conditions. At low solar zenith angles the agreement (± 10%) was quite satisfactory, whereas at high solar zenith angles the broadband instruments gave systematically lower readings than the erythemally weighted spectral data. The deviation of the spectral response of the broadband instruments from the Commission Internationale de 1'Eclairage (CIE) erythema function and the cosine error provide an explanation of the observed differences that are similar for both broadband meters. Model calculations agree quite well with the observations, if an accurate measurement of the broadband spectral response is available. An analytical fit curve was established for the ratio between broadband and weighted spectral data, as a function of solar zenith angle, enabling quick and easy checks of the stability of the spectrora-diometric system. The relative standard deviation of the data from the fit function was only2–3% in the case of cloudless sky conditions and 5% for all sky conditions, including all types of systematic and instrumental errors.     

SOLAR UVR EXPOSURES OF THREE GROUPS OF OUTDOOR WORKERS ON THE SUNSHINE COAST, QUEENSLAND

The solar ultraviolet radiation (UVR) exposures of three groups of outdoor workers, physical education (PE) teachers, ground staff/gardeners and lifeguards were measured using UVR-sensitive polysulfone (PS) film badges. The exposures all took place on the Sunshine Coast, Queensland over 5 consecutive weekdays in November 1992. For the three groups, the shoulder badges received greater UVR exposures than the chest badges, in agreement with previous studies. The PE teachers received the highest UVR exposures while the lifeguards received the least. One of the 5 days of the study was overcast with some rain showers and UVR doses for this day for all groups were significantly lower than on the other 4 days, however the ratio of exposure to ambient remained relatively constant. All groups had measured UVR exposures in excess of occupational guidelines, indicating that protective measures, including education and behavior modification, which are becoming much more common in occupational situations in Australia, are both timely and necessary.     

Ultraviolet Reflection Irradiances and Exposures in The Constructed Environment For Horizontal,Vertical and Inclined Surfaces

Ultraviolet (UV) reflection in the urban constructed environment is not well understood for topical issues such as measuring and modeling the received UV exposure due to that UV reflection for outdoor workers. Both predominantly specular and diffuse reflecting surface types have been identified and investigated for the erythemal UV reflection ratio variation due to solar zenith angle and orientation. This paper presents relationships between erythemal UV reflection ratios measured for non‐horizontal and horizontal surfaces, with predominantly specular surface types indicating stronger relationships with solar zenith angles than diffuse reflecting surfaces types. Erythemal UV exposures caused by the same reflecting surface types at three inclinations are also investigated. Non‐horizontal surfaces can increase erythemal UV exposures compared to erythemal UV exposures received from the same horizontal surface by factors of 1.07–1.46 for specific body sites and by 1.01–1.70 for averages of group body sites for zinc aluminium coated steel sheeting.     

Solar Ultraviolet Radiation Exposure Proxy‐estimated by Sky View Fish‐eye Photography—Potentials and Limitations from an Exploratory Correlation Study

Potentials and limitations of sky view fish‐eye photography and calculation of the percentage of free sky (sky view factor, SVF) as a proxy to estimate solar ultraviolet radiation (UVR) exposure in shade settings are investigated using controlled situations. SVF and measured solar UVR exposure correlated at high mid‐latitude (56.65°N) near autumnal equinox in September. The correlation was enhanced by splitting the sky view images into a south‐ and a north‐half and weighting the south‐half higher to account for the direct sun. Sky view images from eight different settings with SVF‐values 98.3% – 14.9% were compared to exposure measurements by polysulphone film dosimeter badges in the horizontal zenith‐, vertical‐south‐, east‐, west‐ and north‐directions and their combinations. The sky view images were un‐split and un‐weighted or split and the semi‐skies given south/north weights (3.0/1.0) or a higher weight ratio (3.5/0.5). Of all tested combinations split sky view SVFs weighted 3.0/1.0 and compared to horizontal (zenith‐oriented) dosimeters yielded the highest correlation (R² = 0.96). The weight ratio (3.5/0.5) yielded the 2^nd highest correlation (R² = 0.90) both compared to measured horizontal exposure and compared to the horizontal exposure averaged with the vertical‐south‐oriented exposure. SVF from sky view fish‐eye photography may estimate solar UVR exposure in shade settings.     

Solar Ultraviolet Radiation Exposure and Sun Protection Behaviors and Knowledge Among a High‐Risk and Overlooked Group of Outdoor Workers in South Africa

The exposure of outdoor car guards to solar ultraviolet radiation (UVR), the majority with deeply pigmented skin, to solar UVR was measured for five consecutive days during early spring (September 2017) in South Africa using electronic UVR dosimeters attached to the upper arm of each participant. The exposure of the nape of the neck, forehead, nose, cheek and hand was extrapolated from the measurements. The onsite ambient solar UVR on a flat, horizontal, unshaded surface was measured concurrently. The sun‐related knowledge, behavior and attitudes of the car guards were evaluated using questionnaires. Total personal daily solar UVR exposure as a percentage of the ambient solar UVR exposure was 24%. The exposure of car guards on several body sites was in excess of the occupational threshold limit value. Sleeved shirts and hats were the most commonly used sun protection measures (worn by 70% and 80%, respectively). Considering the high levels of solar UVR reported on most days throughout the year in South Africa, more studies quantifying the personal exposure of outdoor workers in both the informal and formal sectors are necessary.     

PERSONAL DOSIMETRY OF SOLAR UV RADIATION FOR DIFFERENT OUTDOOR ACTIVITIES

Abstract Quantifying individual exposure to ultraviolet radiation (UVR) is critical to understanding the etiology of a number of diseases including nonmelanotic and melanotic skin cancers. Measurements of personal exposure to solar UVR were made in Hobart, Tasmania in February (summer) 1991 for six different outdoor activities using UVR-sensitive polysulfone (PS) film attached at seven anatomical sites. Concurrent behavioral and environmental observations were also made. To date many studies have relied on subject recall to quantify past solar UVR exposures. To gain insight into the accuracy of subject recall the measured UVR exposures received by different subjects using the PS film were compared to those calculated from personal diaries and ambient solar UVB levels from a monitoring station. In general, when UVR exposure activities took place under close supervision, good correlations were obtained between the PS badges and the ambient measurements/diaries approach. Ultraviolet radiation exposures for the field study involving 94 subjects engaged in a number of outdoor activities are presented.     

Sunburn Risk Among Children and Outdoor Workers in South Africa and Reunion Island Coastal Sites

To estimate potential sunburn risk for schoolchildren and outdoor workers, ground‐based ambient solar ultraviolet radiation (UVR) measurements were converted into possible child (5% of ambient solar UVR) and outdoor worker (20% of ambient solar UVR) solar UVR exposures by skin type and season for three coastal sites: Durban, Cape Point (South Africa) and Saint Denis (Reunion Island, France). Cumulative daily ambient solar UVR levels were relatively high at all sites, especially during summer, with maximum values of about 67, 57 and 74 Standard Erythemal Dose (SED) (1 SED = 100 J m^?2) at Durban, Cape Point and Saint Denis respectively. Sunburn risk was evident for both children and outdoor workers, especially those with skin types I and II (extremely to moderately sensitive) during summer, early autumn and/or late spring at all three sites. Although results need to be verified with real‐time, instantaneous and nonintegrated personal solar UVR measurements, this understanding of sunburn risk is useful for initiating the development skin cancer prevention and sun protection awareness campaigns in both countries.     

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.     

Solar UVR Exposures of Primary School Children at Three Locations in Queensland

Abstract— The ultraviolet radiation (UVR) exposures of primary school children in Brisbane, Toowoomba and Mackay (latitudes 27°30', 27°33' and 21°15' south, respectively) were assessed over a period of 2 weeks at each location using UVR-sensitive polysulfone (PS) film badges attached at the shoulder. The students filled in questionnaires on their time spent outdoors for each day of the study. These data in conjunction with the ambient UVR measured by a detector/datalogger unit at each site were used to correlate the calculated exposures with those measured using the PS badges. Overall, the questionnaires indicated that the males spent more time outdoors and had higher measured UVR exposures than females. For both boys and girls at each location, there was a strong correlation between the mean measured UVR exposure and the ambient solar UVR at that location.     

Measured solar ultraviolet radiation exposures of outdoor workers in Queensland in the building and construction industry

The risk to outdoor workers of exposure to solar ultraviolet radiation (UVR) has been known for some time, particularly in the building and construction industry, where workers often use little in the way of protection against solar UVR. In recent years there have been attempts by authorities in Australia and in Queensland in particular, where UVR levels in spring and summer are very high to extreme, to instigate and to encourage the use of personal UVR protection by outdoor workers. To quantify UVR exposure of building and construction industry workers involved in typical outdoor work, a study was conducted using UVR-sensitive polysulphone film badges. The results indicated that the doses were significant, often well in excess of recommended exposure limits. The measured exposures varied between trades. Data on the use of personal UVR-protective equipment and the skin type of workers were also collected. Many of the workers had skin types that were sensitive to UVR and showed signs of sunburn. In summary, the study found that at-risk individuals were exposed to extreme levels of UVR, in most cases without adequate and appropriate sun protection.     

MIDDLE ULTRAVIOLET RADIATION REACHING THE OCEAN SURFACE*

Abstract— Direct measurements of the downwelling spectral irradiance in the middle UV (280–340 nm) have been made for a range of solar zenith angles (20°-70°). These measurements were made for a marine atmosphere at equatorial latitudes. We fit these data to two semi-empirical analytic representations, from which quantitative calculations of spectral irradiance in the middle UV incident at the ocean surface can be made. The formulae accommodate variation in wavelength, solar zenith angle, ozone thickness, aerosol thickness and surface albedo. Our purpose is to provide marine photobiologists and photochemists with a basis for estimating middle UV radiation levels reaching the ocean surface and the approximate changes caused by manmade alterations of the ozone layer.     

Estimation of the annual solar UVR exposure dose of infants and small children in tropical Queensland, Australia

The solar ultraviolet radiation (UVR) exposure of infants and small children was measured for 1 week using UVR-sensitive polysulfone film attached to the shoulder and chest of the subjects. For the infant study, shoulder and chest badges received similar exposures, while the 2 1/2-year-olds received higher exposures on the shoulder than on the chest. Also, the 2 1/2-year-olds generally received higher exposures than the infants. The median total daily exposures for both groups were 39 and 92 J/m2. The maximum total daily exposures measured were 640 J/m2 (chest) and 240 J/m2 (shoulder) for the infants and 2060 J/m2 (shoulder) and 840 J/m2 (chest) for the 2 1/2 year-olds. Using this exposure data, monthly and annual exposure doses were calculated for both groups and compared to similar data from the UK. The annual exposure dose for infants is 8.4 kJ/m2 or 84 standard erythemal dose (SED) for both shoulder and chest. The annual exposure dose for 2 1/2 year-old children is 39.4 kJ/m2 or 394 SED for the shoulder and 28.8 kJ/m2 or 288 SED for the chest. Apart from the generally higher annual exposure doses experienced by the infants and 2 1/2 year-old children in Townsville, the main difference to the UK is the almost nonexistent drop in monthly exposure doses between summer and winter in Townsville compared to the UK. In the UK, the winter-month exposure dose is only 0.5% of the summer-month dose. However, in Townsville it is around 40%.     

A Comparison of Solar Ultraviolet Radiation Exposure in Urban Canyons in Venice,Italy and Johannesburg,South Africa

Urban environments can have high-risk spaces that can provide excess personal sun exposure, such as urban or street canyons, and the spaces between buildings, among others. In these urban spaces, sun exposure can be high or low depending on several factors. Polysulphone film (PSF) was used to assess possible daily solar ultraviolet radiation (UVR) exposure in urban canyons in Venice, Italy and, for the first time in Africa, in Johannesburg, South Africa. The photodegradation of PSF upon solar exposure was monitored at a wavelength of 330 nm by ultraviolet-visible spectrophotometry, and the resultant change was converted to standard erythemal dose (SED) units (1 SED = 100 J m⁻²). Mean daily ambient solar UVR exposure measured for Venice and Johannesburg ranged between 20–28 SED and 33–43 SED, respectively. Canyon-located PSF exposures were lower in Venice (1–9 SED) than those in Johannesburg (9–39 SED), depending mainly on the sky view factor and orientation to the sun. There was large variation in solar UVR exposure levels in different urban canyons. These preliminary results should be bolstered with additional studies for a better understanding of excess personal exposure risk in urban areas, especially in Africa.     

The Simulated Ocular and Whole-Body Distribution of Natural Sunlight to Kiteboarders: A High-Risk Case of UVR Exposure for Athletes Utilizing Water Surfaces in Sport

Kiteboarding is an aquatic sporting discipline that has not yet been considered in the literature to date in terms of solar ultraviolet radiation (UVR) measurement. Kiteboarders need to look upward and are placed obliquely relative to the horizon when towed behind an overhead kite over a reflective water surface. This research defines the typical body surface orientation of a kiteboarder in motion through video vector analysis and demonstrates the potential risk to ocular and skin surface damage through practical measurement of solar UVR using a manikin model. Video analysis of 51 kiteboarders was made to construct skeletal wireframes showing the surface orientation of the leg, thigh, spine, humerus, lower arm and head of a typical kiteboarder. Solar UVR dosimeter measurements made using a manikin model demonstrate that the vertex and anterior surfaces of the knee, lower leg and lower humerus received 89%, 90%, 80% and 63% of the available ambient UVR, respectively, for a typical kiteboarder who is tilted back more than 15° from vertical while in motion. Ocular (periorbital) exposures ranged from 56% to 68% of ambient. These new findings show that the anterior skin surfaces of kiteboarders and the eye are at elevated risk of solar UVR damage.     

Seasonal erythemal UV doses in Belo Horizonte, Brazil

The ultraviolet radiation (UVR) emitted by the Sun causes many effects on the biosphere. On human beings they vary from the benefit of vitamin D synthesis to the harm of skin cancer induction. The biological dose depends on the effect, the exposure time to the Sun and the amount of UVR received. In this work we show that the measured incidence of erythemal dose (ED) in Belo Horizonte (19.92 degrees S, 43.94 degrees W, 858 m a.s.l., Brazil) for a cloudless day can vary from 7503 to 2926 J m(-2) in the summer-winter seasonal variation. In addition, supposing a linear relationship between the ED and the geophysical parameters of solar zenith angle cosine (cos(SZA)), column ozone and reflectivity from the ozone monitoring instrument overpass measurements, a model for the forecast of UVR incidence on a monthly-based period is developed. From this an annual ED of 1,451,099 J m(-2) is obtained.     

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.     

Evaluation of the Long‐term Cumulative UVA Facial Exposure of Queensland School Teachers derived for an Extended Period from the OMI Satellite Irradiance

This research presents a novel methodology for deriving the total daily broadband solar UVA (320–400 nm) received by school teachers during their working day from Ozone Monitoring Instrument (OMI) satellite solar noon UVA irradiance measurements for a Queensland subtropical site (27.5°S, 152°E). Daily UVA exposures are weighted to the anatomical human cheek (anterior infra‐orbital region) for teachers wearing and not wearing broad‐brimmed hats. The method utilizes the OMI UVA irradiance data collected daily at high temporal resolution over 2005 to 2016 to derive the total daily UVA exposure to a horizontal plane. These horizontal plane exposures are scaled by factors to take into account the timing of outdoor activity. The relationship between exposures to a horizontal plane and those to a vertical plane and the protection provided by a broad‐brimmed hat was assessed to evaluate the total daily UVA exposures to the cheek for classroom and physical education teaching staff expected to be outside at different periods of the day. The developed method enables the total daily UVA exposure to specific anatomical sites to be evaluated from the satellite solar noon irradiance at locations that do not have access to surface‐based instrumentation capable of recording in the solar UVA waveband.     

Albedo-enhanced maximum UV irradiance--measured on surfaces oriented normal to the sun

UV radiation measured on normal-to-the-sun-oriented surfaces can show significantly higher global UV irradiance values compared to measurements on horizontal receivers. The direct component is amplified by the inverse cosine of the zenith angle, but over surfaces with high local albedo this accounts for only about half of the signal rise of global irradiance. The signal rise of the diffuse component, however, is strongly related to local albedo and solar elevation, which is demonstrated by 2 years of measurements of direct, diffuse, global, reflected and global normal-to-the-sun erythemal effective UV irradiance (UVery). Global UVery signal rises, on normal-to-the-sun-oriented versus horizontal receivers, of up to 65% were measured on fresh snow and solar elevation angles below 30 degrees. An empirical expression has been deduced from the measurements relating the ratio of normal-to-the-sun versus horizontal measurements of global UVery to surface albedo and solar elevation. This allows one to calculate the maximum global UVery irradiance levels which are to be expected on normal-to-the-sun-oriented surfaces with respect to horizontal measurements or model calculations.     

On the importance of spectral responsivity of Robertson-Berger-type ultraviolet radiometers for long-term observations

A system to determine the spectral responsivity of ultraviolet (UV) radiometers has been developed and is routinely operated at the Central Ultraviolet Calibration Facility, at the National Oceanic and Atmospheric Administration. The instrument and the measurement methodologies are described. Results of measurements from thermally controlled broadband UV radiometers of the Robertson-Berger (R-B)-type are described. Systematic differences in the spectral response curves for these instruments have been detected. The effect of these differences on the field operation of UV-B radiometers has been studied by calculating the instrumental response from modeled UV spectra. The differences of the weighted spectral UV irradiances, measured by two radiometers with different spectral response functions, caused by the daily variation in the position of the sun were estimated for fixed values of total ozone, altitude and albedo, and for cloud-free conditions. These differences increase with the solar zenith angle and are as large as 8%. Larger differences in the instrumental response may be produced by ozone variations. Thus, care must be taken when analyzing data from R-B radiometers and comparing results from different instruments. Routine cycling of UV-B radiometers in operative networks without a careful determination of the spectral responsivity, or small drifts of the spectral responsivity, may strongly affect the accuracy of UV radiation measurements and produce an erroneous trend. Because of the possible differences among radiometers, it would not be practical to derive the long-term behavior of UV radiation without routine and thorough characterization of the spectral responsivities of the instruments.