Measurement of UVA Exposure to Solar Radiation

Exposure to solar UVA (320–400 nm) radiation can damage DNA and lead to skin disorders. Conventional dosim-etry using a single piece of polysulfone or diglycol carbonate (CR-39) cannot provide accurate measurement of the biologically effective irradiance for erythema for the UVA waveband. A package employing four dosimeters (polysulfone, nalidixic acid, 8-methoxypsoralen and phe-nothiazine) has been shown to be effective for use as a spectrum evaluator for evaluating the UVA source spectrum. In Brisbane, on a horizontal position, the spectrum evaluator requires about 5 min exposure in summer and about 20 min in winter. This amounts to about 10 mJ cm-² of erythemal UV radiation.     

Horizontal and sun-normal spectral biologically effective ultraviolet irradiances

The dependence of the spectral biologically effective solar UV irradiance on the orientation of the receiver with respect to the sun has been determined for relatively cloud-free days at a sub-tropical Southern Hemisphere latitude for the solar zenith angle range 35-64 degrees. For the UV and biologically effective irradiances, the sun-normal to horizontal ratio for the total UV ranges from 1.18 +/- 0.05 to 1.27 +/- 0.06. The sun-normal to horizontal ratio for biologically effective irradiance is dependent on the relative effectiveness of the relevant action spectrum in the UV-A waveband. In contrast to the total UV, the diffuse UV and diffuse biologically effective irradiances are reduced in a sun-normal compared with a horizontal orientation by a factor ranging from 0.70 +/- 0.05 to 0.76 +/- 0.03.     

Direct comparison between the angular distributions of the erythemal and eye-damaging UV irradiances: a pilot study

Several broadband ultraviolet (UV) radiation angular distribution investigations have been previously presented. As the biologically damaging effectiveness of UV radiation is known to be wavelength dependent, it is necessary to expand this research into the distribution of the spectral UV. UV radiation is also susceptible to Rayleigh and Mie scattering processes, both of which are completely wavelength dependent. Additionally, the majority of previous measurements detailing the biologically damaging effect of spectral UV radiation have been oriented with respect to the horizontal plane or in a plane directed towards the sun (sun-normal), with the irradiance weighted against action spectra formulated specifically for human skin and tissue. However, the human body consists of very few horizontal or sun-normal surfaces. Extending the previous research by measuring the distribution of the spectral irradiance across the sky for the complete terrestrial solar UV waveband and weighting it against erythemal, photoconjunctivital and photokeratital action spectra allowed for the analysis of the differences between the biologically effective irradiance (UV(BE)) values intercepted at different orientations and the effect of scattering processes upon the homogeneity of these UV(BE) distributions. It was established that under the local atmospheric environment, the distribution profile of the UV(BE) for each biological response was anisotropic, with the highest intensities generally intercepted at inclination angles situated between the horizontal and vertical planes along orientations closely coinciding with the sun-normal. A finding from this was that the angular distributions of the erythemal UV(BE) and the photoconjunctivital UV(BE) were different, due to the differential scattering between the shorter and longer UV wavelengths within the atmosphere.     

An Analysis of UVA Emissions from Sunlamps and the Potential Importance for Melanoma

Abstract— Exposure to solar UV radiation is a risk factor for cutaneous malignant melanoma (CMM). Epidemiologic studies have also considered the use of sunlamps as a possible contributor to CMM. We measured and analyzed the emission spectra of six different currently marketed sunlamps and a historical sunlamp, the UVB-emitting FS lamp, and compared the results to solar exposure. For a typical tanner (20 sessions @ 2 minimal erythema doses (MED)/session), the annual UVA doses from commonly used fluorescent sunlamps were 0.3-1.2 times that received from the sun. For a frequent tanner (100 sessions @ 4 MED/session), the annual UVA doses from fluorescent sunlamps were 1.2-4.7 times that received from the sun and 12 times for recently available, high-pressure sunlamps. To determine biologically effective doses, action spectra for squamous cell carcinoma (SCC) in humans and for melanoma in the Xiphophorus fish (XFM) were applied to the sunlamps' emission spectra. The results for the effective doses using the SCC action spectrum tracked the UVB doses, while the results using the XFM action spectrum tracked the UVA doses. When combined with UV exposure received from the sun, typical sunlamp use results in an approximate doubling of annual effective dose, if the XFM action spectrum is applied. Frequent use, however, can increase the annual effective XFM dose by as much as 6 times what would be received from the sun alone for fluorescent sunlamps and as much as 12 times for newer, high-pressure sunlamps.     

Occupational UV Exposure of Environmental Agents in Valencia,Spain

Excessive exposure to ultraviolet radiation (UVR) is considered the most important environmental risk factor in the development of melanoma and skin cancer. Outdoor workers are among those with the highest risk from exposure to solar UVR, as their daily activities constantly expose them to this radiation source. A study was carried out in Valencia, Spain, in summer 2012 and involved a group of 11 workers for a period of six 2‐day recordings. Sensitive spore‐film filter‐type personal dosimeters (VioSpor) were used to measure erythemal UVR received by environmental agents in the course of their daily work. Median 2‐day UV exposure was 6.2 standard erythema dose (SED), with 1 SED defined as effective 100 J m^?2 when weighted with the Commission Internationale de L′Eclairage's (CIE) erythemal response function. These workers were found to receive a median of 8.3% total daily ambient ultraviolet erythemal radiation. Comparison with the occupational UV exposure limit showed that the subjects had received an erythemal UV dose in excess of occupational guidelines, indicating that protective measures against this risk are highly advisable.     

Lower body anatomical distribution of solar ultraviolet radiation on the human form in standing and sitting postures

Humans undertake their daily activities in a number of different postures. This paper aims to compare the anatomical distribution of the solar erythemal UV to human legs for standing and sitting postures. The exposure ratios to the legs (ratio of the UV exposure to a particular anatomical site compared to the ambient) have been measured with UV dosimeters for standing and sitting postures of a manikin. The exposure ratios for the legs ranged from 0 to 0.75 for the different anatomical sites for the sitting posture in summer (December through February) compared to 0.14 to 0.39 for the standing posture. In winter (June through August) the exposure ratios ranged from 0.01 to 0.91 for sitting to 0.17 to 0.81 for standing. For the anterior thigh and shin, the erythemal UV exposures increased by a factor of approximately 3 for sitting compared to standing postures. The exposure ratios to specific anatomical sites have been multiplied by the ambient erythemal UV exposures for each day to calculate the annual exposures. The annual erythemal exposures to the anterior thigh and ankle were predicted to be higher than 800 MED for humans sitting outdoors each day between noon and 13:00 h Australian Eastern Standard Time (EST). For humans standing outdoors during this time, the annual erythemal UV exposure averaged over each leg site was 436 MED, whereas, the averaged annual erythemal UV exposure was 512 MED for the sitting posture. Similarly, the annual erythemal UV exposure averaged over each of the sites was 173 MED for humans standing outdoors between 09:00 h EST and noon each Saturday morning and 205 MED for humans sitting outdoors during this time. These results show that there is increased risk of non-melanoma skin cancer and malignant melanoma to the lower body if no UV preventative strategies are employed while in a sitting posture compared to a standing posture.     

A solar erythemal (sunburn) radiation dosimeter

Measurement of solar erythemal radiation is a technically demanding task because it is accompanied by a vastly greater flux of other solar radiation. An inexpensive solar erythemal radiation dosimeter has been designed which is based on the photocleavage of an alkyl disulphide. The reaction is carried out in a hydrocarbon solvent which can readily donate hydrogen atoms and as a result no polysulphides with absorptions in the erythemal action spectrum were formed. This avoided non-linearities in the dosimeter arising from inner filtering effects. The amount of alkylthiol produced as a result of exposure of the corresponding dialkyl disulphide solution to solar erythemal radiation was linearly related to the dose of radiation received.     

Diffuse component of solar ultraviolet radiation in tree shade

The first set of quantitative data of diffuse erythemal UV and UV-A radiation in tree shade at a sub-tropical Southern Hemisphere latitude is presented. Over the summer, approximately 60% of the erythemal UV radiation in tree shade is due to the diffuse component. Similarly, approximately 56% of the UV-A radiation in tree shade is due to the diffuse component. In tree shade these diffuse UV percentages are relatively constant from the morning to noon to afternoon periods. In comparison, in full sun, there is a decrease in the percentage of diffuse UV from morning to noon to afternoon. The exposures to diffuse UV on a horizontal plane in tree shade between 9:00 EST and 15:00 EST are of the order of 4 MED (minimum erythemal dose) and 14 J cm(-2) for erythemal UV and UV-A, respectively. The high diffuse UV component in the shade may result in high UV exposures not only to unprotected parts of the body on a horizontal plane, but also in equally high UV irradiances to parts of the body, including the eyes and face, that are not UV protected.     

Sensitivity of biologically active UV radiation to stratospheric ozone changes: effects of action spectrum shape and wavelength ranges

Biological action spectra are commonly used to assess health and ecosystem responses to increases in spectral ultraviolet (UV) irradiances resulting from stratospheric ozone (O3) reductions. For each action spectrum, a normalized sensitivity coefficient (the radiation amplification factor [RAF]) can be calculated as the relative increase in biologically active UV irradiance for a given relative decrease in the atmospheric O3 column amount. We use a detailed radiative transfer model to calculate the dependence of RAF on the O3 column amount and the solar zenith angle (and, therefore, implicitly on latitude and season) for several commonly used action spectra. A simple analytical model is used to interpret the results in terms of the semilogarithmic slope of the action spectra in the UV-B and UV-A wavelength ranges. We also show that RAF may be overestimated substantially if the UV-A portion of an action spectrum is significant but is neglected. This is illustrated using several idealized action spectra as well as published action spectra for plant responses to UV irradiation. Generally, if the portion of an action spectrum measured longward of approximately 300 nm spans less than about two orders in magnitude in its sensitivity, significant errors in the estimated RAF may ensue, and the use of this action spectrum in O3-related studies can be compromised.     

POTENTIAL EFFECTS OF ALTERED SOLAR ULTRAVIOLET RADIATION ON HUMAN SKIN CANCER

There is highly significant evidence that non-melanoma skin cancers are primarily due to chronic repeated exposure to solar ultraviolet radiation, and that there is a significant, although somewhat different relationship between solar radiation and the development of cutaneous malignant melanoma. Recent experimental and epidemiologic studies show that the biologically most effective UVR wavelengths are in the segment of the solar UVR spectrum that would be significantly augmented by decreases in stratospheric ozone content. A recent report on measurements of column ozone changes in the stratosphere has shown that in the past 18 yrs, there has been an ozone decrease between 2 and 3%, greater in the winter months, and somewhat differing with latitude in the Northern Hemisphere. Calculations of the relationship of ozone decrease to increase in biologically effective UVR show great dependence on the biologic action spectrum assumed. Based on extensive epidemiologic studies of skin cancer incidence, it appears that the estimated increase in biologically effective UVR due to the measured ozone decreases in the past (almost) two decades are not likely to be the cause of the sharp increase in skin cancer incidence which have been observed. Most likely these increases in incidence are the result of increasing personal exposure, due to striking changes in personal behavior that have taken place for social reasons. However, there is every reason to believe that increases in biologically effective UVR due to stratospheric ozone decreases will have significant impact on human skin cancer incidence in the future.     

IMPACT OF ENHANCED SIMULATED SOLAR ULTRAVIOLET RADIATION UPON A MARINE COMMUNITY

Abstract—There is evidence to indicate that an increased exposure to solar radiation in the UV-B region (specifically, 290–320 nm) may occur as a result of anthropogenic degradation of stratospheric ozone. The fact that present levels of solar UV radiation can detrimentally affect marine organisms led to experiments to quantify the impact of increased UV radiation upon a marine community. Two 720–l seawater chambers (continuous flow-through design) were exposed to simulated solar UV radiation. Fluorescent sunlamps filtered by a 290 nm cutoff filter (a 0.13 mm thickness of cellulose triacetate film) were used as the radiation source. Utilization of three different weighting factors for the spectral irradiances at the surface of the chambers yielded differences of 18%, 35% and 40% in biologically effective fluence rate between the two chambers. Analysis of attached forms of algae at various depths demonstrated that a surface exposure of 1.4W/m² in the 290–315nm waveband as contrasted with the chamber receiving a surface exposure of 1.0W/m² resulted in depressed Chl a concentrations, reduced biomass, increased autotrophic indices, and decreased community diversity. These results indicate a potential for adverse effects of increased solar UV-8 radiation: decreased community diversity, community structure shifts, and decreased productivity.     

Erythemal Ultraviolet Exposure in Two Groups of Outdoor Workers in Valencia, Spain

UVexposure is considered to be one of the most important risk factors in skin cancers, mainly in outdoor occupational activities. Outdoor workers receive regular and significant solar UV erythemal radiation (UVER). To quantify the UVER exposure of certain groups of workers, dosimeters are used to measure the biologically effective UV radiation received in the course of their daily work. Two groups of outdoor workers, composed of gardeners and lifeguards, were measured for UVER exposure using sensitive spore-film filter-type personal dosimeters (Viospor). The study took place in Valencia, Spain, in June and July 2008, and involved one group of four gardeners and another of five beach lifeguards for a period of 4 and 6 days, respectively. The gardeners' mean UV exposure was 4.13 ± 0.60 SED day⁻¹, where 1 SED is defined as effective 100 J m⁻² when weighted with the CIE erythemal response function, whereas the lifeguards received 11.43 ± 2.15 SED day⁻¹. The mean exposure ratio (ER) relative to ambient of gardeners was 0.09 ± 0.01 and for lifeguards was 0.27 ± 0.05. ER is defined as the ratio between the personal dose on a selected anatomical site and the corresponding ambient dose on a horizontal plane during the same exposure period. The lifeguards received the highest UVER exposure, although both groups had measured UVER exposure in excess of occupational guidelines, indicating that protective measures are necessary.     

Solar UV Exposure of Seafarers along Subtropical and Tropical Shipping Routes

Seafarers working on decks of vessels at low latitudes are exposed to extremely high solar UV radiation. Their risk of developing skin cancer may be enhanced. Solar erythemal UV irradiance and exposure were measured for the first time on merchant vessels going along typical international routes at low latitudes. The measurements taken at horizontal incidence on the observation deck, and on different parts of the seaman (head, shoulder, chest and back) doing typical outdoor work show the highest portion (40–80% of horizontal exposure) incident on the head. 2 years of measurements of solar UV and VIS/NIR irradiance taken on the mast top of the Research Vessel METEOR were added to the data base. Radiative transfer model calculations were performed along all the routes with satellite‐based input data of ozone and aerosol for clear sky health‐effective radiation including vitamin D3 (VD3). Measured data show extremely high noontime UV index values up to 19 with clear sky, and up to 22 due to cloud scattering. Eight hours erythemal exposure values are more than double of typical midlatitude summer values. Based on the results, an algorithm is presented to derive a seafarer's personal erythemal exposure according to his/her personal record of sea service.     

UV index forecasts and measurements of health-effective radiation

While erythemal irradiance as a potentially damaging effect to the skin has been extensively studied and short-term forecasts have been issued to the public to reduce detrimental immediate and long-term effects such as sunburn and skin cancer by overexposure, beneficial effects to human health such as vitamin D(3) production by UV radiation and melatonin suppression by blue visible light have attained more and more attention, though both of them have not become part of forecasting yet. Using 4years of solar radiation data measured at the mid-latitude site Lindenberg (52°N), and forecast daily maximum UV index values, an overall good correspondence has been found. The data base of solar UV radiation and illuminance has also been used to analyze effects of clouds and aerosols on the effective irradiance. Optically thick clouds can strongly modify the ratios between erythemal and vitamin D(3) effective irradiance such that direct radiative transfer modeling of the latter in future UV forecasts should be preferably used. If parameterizations of vitamin D(3) effective irradiance from erythemal irradiance are used instead, the optical cloud depth would have to be taken into account to avoid an overestimation of vitamin D(3) with parameterizations neglecting cloud optical depth. Particular emphasis for the beneficial effects has been laid in our study on low exposure. Daily doses of solar irradiation for both vitamin D(3) and melatonin suppression do not reach minimum threshold doses even with clear sky and unobstructed horizon during the winter months.     

Anatomical distribution of solar ultraviolet exposures among cyclists

Exposure to solar ultraviolet (UV) radiation is the major environmental factor implicated in the development of melanoma and other skin cancers, as well as eye damage and skin photoaging. Outdoor recreational activities such as cycling are increasingly pursued for health benefits, however little information is available regarding potential adverse effects of excessive sun exposure in this setting, nor about the anatomical distribution of solar dose. Polysulphone badges (UV dosimeters) were attached to the head, backs of hands and ankles of 22 cyclists during a seven-day charity bicycle ride in Queensland, Australia. Average daily exposures exceeded one minimal erythemal dose (MED) at all body sites except the ankle. Significant differences in UV dose among the various body sites were noted, with highest exposures recorded on the top of the head. Mean doses received at the ankle (0.94 MED), back of the hand (1.28 MED) and side of the head (1.14 MED) were 51%, 71% and 63% of those received at the top of the head (1.80 MED), respectively. These data indicate that cycling exposes adherents to substantial doses of UV radiation. Moreover, our observations suggest that even vertically-oriented, potentially shaded sites such as the lower leg typically receive doses of solar radiation no less than half of maximally exposed sites.     

INCREASED UV EXPOSURE IN FINLAND IN 1993

Abstract—
Exceptionally low total ozone, up to 40% below the normal level, was measured over Northern Europe during winter and spring in 1992 and 1993. In 1993 the depletion persisted up to the end of May, resulting in a significant increase of biologically effective UV radiation. The increases were significantly smaller in 1992 and 1994 than in 1993. The UV exposure of the Finnish population was evaluated through measurements and theoretical calculations. The increase in measured erythemal (International Lighting Commission) UV falling onto horizontal surfaces on clear days was determined relative to model calculations for an average ozone amount. The increase was on average 10% from April to May 1993, and the maximal measured increase was 34%. Theoretical calculations for both erythemal and carcinogenic (Skin Cancer Utrecht-Philadelphia) UV indicated that in 1993 the theoretical annual increase to a vertical (cylinder) surface ranged from 8 to 13% in Finland. The reflection of UV from snow considerably increases facial UV doses in Northern Finland.     

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.     

SPECTRAL QUALITY OF TWO FLUORESCENT UV SOURCES DURING LONG-TERM USE

The characteristics of a fluorescent ultraviolet (UV) lamp (UVB-313), UV-B transmitting cellulose diacetate (CA) and UV-B absorbing polyester (PE) films were determined during actual use. Although lamp emission was stable between 70 and 386 h of burn time (longer times were not investigated), the absorbance of UV-B and UV-A radiation by CA and PE films, respectively, increased with time when wrapped around lamps. As a result, the irradiance of lamp/filter combinations decreased steadily (even when CA films were presolarized for 10 h), making it necessary to compensate by adjusting the height of the lamp bank or by changing filters frequently. Note that corrective action is required for UV-A controls (PE films) as well as UV-B experimental treatments (CA films). Changing filters is preferable, since aging of CA filters caused shifts in the ratio of UV-B to UV-A. However, in spite of these shifts, the normalized spectrum of weighted biologically effective UV-B radiation did not change to a large extent.