A CLIMATOLOGY OF SUNBURNING ULTRAVIOLET RADIATION

Abstract— Data are presented from 14 sites where continuous measurements of the sun's shortest ultraviolet radiation reaching the earth's surface have been made for four or more years. Average daily dose per month and its variability from year to year is shown for each station. Some of the many influences affecting these measurements can be discerned by station intercomparisons. No consistent long term change in solar UV-B radiation reaching the ground is evident.     

聚丙烯膜表面光接枝聚合

对聚合物表面进行接枝聚合是一种有效的材料改性方法。近年来,S.Tazuke,Y.Ogiwara,高志民等人做了一些用紫外光引发接枝方面的工作,获得了较满意的结果。为提高聚丙烯(简称为PP)膜的光稳定性,我们研究了将一种受阻胺类光稳定剂,甲基丙烯酸2,2,6,6-四甲基哌啶醇酯(简称为MTMP)光接枝到PP膜表面的聚合过程。     

THE OCULAR DOSE OF ULTRAVIOLET RADIATION FROM SUNLIGHT EXPOSURE

Abstract— The ocular toxicity of ultraviolet radiation has been demonstrated in acute photokeratitis and is suspected of contributing to cataractogenesis and senile macular degeneration. While previous studies have emphasized photochemical and epidemiologic aspects of ocular UV-B irradiation, little is known about the extent of such exposure in human subjects. To determine levels of ocular UV-B exposure from sunlight, four mannikin headforms were fitted with UV-B sensitive film (polysulphone) and exposed on an unobstructed rooftop (Baltimore, Md.: latitude = 39.5 degrees) to four hours of sunlight (11 am-3 pm local time) over a three month period (June-August). Simultaneous measurements of ocular and ambient exposure revealed a ratio of 19.5 ± 2.9% that was independent of ambient level (P < 0.05). Measurements performed during earlier hours (8 am-11 am) revealed a similar ratio. Mannikin headforms fitted with brimmed baseball caps showed a22–95% reduction in ocular exposure, depending on the angle of the hat brim to the forehead. Three sets of spectacles substantially reduced ocular UV-B exposure,62–94% dependent on the absorption properties of the spectacle lenses. These anthropomorphic measurements indicate that a substantial percentage of ambient UV-B light is incident upon the cornea and that personal factors, such as wearing a hat or spectacles, can markedly affect UV-B exposure.     

ULTRAVIOLET RADIATION IN ANTARCTICA: INHIBITION OF PRIMARY PRODUCTION

With the seasonal formation of the ozone hole over Antarctica, there is much concern regarding the effects of increased solar UV-B radiation (280–320 nm) on the marine ecosystem in the Southern Ocean. In situ incubations of natural phytoplankton assemblages in antarctic waters indicate that under normal ozone conditions UV-B radiation is responsible for a loss of approximately 4.9% of primary production in the euphotic zone, whereas UV radiation with wavelengths between 320 and 360 nm causes a loss of approximately 6.2%. When combined with data on the action spectrum for photoinhibition by UV radiation, our data suggest that the enhanced fluence of UV-B radiation under a well-developed ozone hole (150 Dobson units) would decrease daily primary productivity by an additional amount of 3.8%. Calculations that take into consideration the extent and duration of low stratospheric ozone concentrations during September to November indicate that the decrease in total annual primary production in antarctic waters due to enhanced UV-B radiation would be 0.20%.     

THE VASCULAR RESPONSE OF HUMAN SKIN TO ULTRAVIOLET RADIATION

The vascular response of human skin to 300 nm (UV-B) and 254 nm (UV-C) ultraviolet radiation was assessed using the reflectance measurement of erythema and the technique of laser Doppler velocimetry. For both wavelengths, the increase in measured Doppler blood flux varied with the increase in erythema in a quadratic manner predicted by a simple model based on the principles of fluid mechanics. This suggests that the mean red blood cell velocity increases significantly in areas of UV-B and UV-C erythema. No qualitative difference in response to these two wavelengths was demonstrated, suggesting that the same blood vessels are involved in the causation of both UV-B and UV-C erythema.     

THE DOSE-RESPONSE RELATIONSHIP OF TUMORIGENESIS BY ULTRAVIOLET RADIATION OF 254 nm

Abstract— Groups of albino hairless mice, Skh-hrl, were exposed daily to UVC radiation from low pressure Hg arcs (Philips TUV 40W). These lamps emit predominantly radiation of 254 nm. Three groups of animals were used in the experiments, each receiving a different daily dose.
The results were described with the Weibull probability function. As in earlier studies with UVB. the tumor induction time was proportional to a power of the daily dose. The exponent turned out to be as low as -0.2. This implies that the induction time varied only a little with the daily dose. The average number of tumors per animal was proportional to a power of time. A sample of 73 tumors of at least 4 mm in diameter were investigated histologically. The large majority were classified as squamous cell carcinomas.
A comparison was made with the results of an earlier reported experiment with Westinghouse FS40 sunlamps. Throughout the whole range of daily doses used in the present experiment, UVC was less carcinogenic than UVB. An intriguing difference between the two types of radiation was that the tumors induced by UVC appeared much more scattered over the irradiated parts of the animals than the UVB-induced tumors.     

SKIN CANCER AND ULTRAVIOLET RADIATION

Abstract. A new model is presented for the calculation of the increased incidence of non-melanoma skin cancer in Caucasians resulting from ozone reduction. The model postulates that the probability of first incidence of such skin cancer is distributed log-normally as a function of total accumulated lifetime dose of harmful ultraviolet radiation. The effect on skin cancer incidence of an increase in harmful ultraviolet radiation due to ozone reduction can then be calculated directly from the extent to which each individual's lifetime accumulated dose is thereby increased. The result of such a perturbation, on average, would be to cause skin cancer to appear at a slightly earlier age. Since skin cancer is predominantly a disease of the elderly, this shift to younger ages has the effect, when integrated over the entire population, of increasing the overall total incidence of skin cancer.     

INACTIVATION OF A RHIZOBIUM BACTERIO-PHAGE BY ULTRAVIOLET RADIATION OF DIFFERENT WAVE-LENGTHS

Abstract— The action spectrum for inactivation of a Rhizobiurn bacteriophage by U.V. radiation follows the shape of the absorption spectrum of DNA between the wave-lengths of 240 and 290 mμ (where inactivation probably reflects damage to the nucleic acid only), and deviates sharply upwards at wave-lengths shorter than 240 mμ (where inactivation may depend on damage to both the nucleic acid, and protein of the phage). The rate of inactivation follows first order kinetics approximately at all wave-lengths tested. Infectivity of the phage is halved when each mg of the phage nucleic acid has absorbed about 0 08 J of radiation energy at any wave-length between 240 and 290 mμ.
The bacteriopharge can be photoreactivated after inactivation at any wave-length between 230 and 290 mμ, but less so after inactivation at 230 mμ than at any wave-length above 240 mμ. No evidence was found to suggest that dimerization of thymine residues of the phage-DNA plays any part in the mechanism of inactivation of the bacteriophage by U.V. radiation.     

MEASUREMENTS OF SOLAR MIDDLE ULTRAVIOLET RADIATION IN A DESERT ENVIRONMENT

Abstract— In this study measurements are reported that were carried out between August 1983 and December 1985 on the solar middle ultraviolet radiation (UVB-280-320 nm) in Kuwait (29.5°N). These measurements are based primarily on polysulfone film detectors. Comparative measurements were also made on a Robertson-Berger meter and a spectroradiometer. The results reported include the daily variation of the solar UVB between 11:30 a.m. and 12:00 noon over the year, the diurnal variation, as well as the amount of UVB as a function of the receiving angle with the horizontal.
Based on these data the polysulfone films were found to be reliable and inexpensive detectors, giving results similar to those of the R-B meter. The diurnal variation of the solar UVB was found to vary as sin2q, where q is an angle that corresponds to the time since sunrise compared to the sunrise-sunset interval times 180. An empirical equation is developed that gives the maximum UVB as a function of the time of day and day of year. A correlation is determined of the polysulfone readings with the spectroradiometric and the R-B meter measurements. The solar insolation was found to be independent of the receiving angle with the horizontal in the winter months and develops into a cosine dependence in the summer months.     

EFFECTS OF ULTRAVIOLET RADIATION ON THE IMMUNE SYSTEM IN HUMANS

In experimental animals, exposure to UV-B radiation produces selective alterations of immune function which are mainly in the form of suppression of normal immune responses. This immune suppression is important in the development of nonmelanoma skin cancer, may influence the development and course of infectious disease and possibly protects against autoimmune reactions. The evidence that this form of immune suppression occurs in humans is less compelling and very incomplete. The wavelengths of radiation most affected by a depletion of the stratospheric ozone layer are those known to be most immunosuppressive in animals and it is likely that such depletion will increase any suppressive effect of sunlight on immunity in humans. In addition to establishing whether or not UV-B radiation can cause suppression of immune function in humans, studies are required to determine if melanin can provide protection against such suppression, the role of this suppression in the pathogenesis of skin cancer, the development of infectious disease and vaccine effectiveness, and the capacity for humans to develop adaptive, protective mechanisms which may limit damage from continued exposure to UV-B radiation.     

THE ROLE OF SOLAR ULTRAVIOLET RADIATION IN 'NATURAL' WATER PURIFICATION

Abstract— The concentration of Escherichia coli in the input and output of a tertiary wastewater system (4 lagoons) has been monitored over an 11 month period. The integrated flux of biologically active solar ultraviolet (UV) radiation was measured during this period. By also determining (1) the effective temperature in the system, (2) the growth rate of E. coli at the effective temperature, (3) the penetration of the solar UV into the lagoons, (4) the dose-response relation for killing of E. coli by UV and (5) the retention time of water in the system, it is possible to compare the 'die off' expected from solar UV exposure to the actual 'die off' observed for different batches of water.
The observed killing of E. coli was quite close to the values calculated, considering the numerous factors involved. Solar UV light would thus seem to be a very important factor in the natural purification of water. Because each successful species must possess characteristics (physiological or behavioral) which provide adequate resistance to solar UV, the ecological role of solar UV radiation has not been widely appreciated.     

ULTRAVIOLET SOLAR RADIATION IN THE HIGH LATITUDES OF SOUTH AMERICA

Abstract Measurements of the UV solar irradiance are available from Ushuaia, Tierra del Fuego during the spring and summer seasons of 4 consecutive years beginning in 1989. In addition, column ozone amounts derived from satellite-based measurements exist for this location over the entire period from 1980 through 1991. Monthly mean column ozone over Ushuaia shows a general decline over the observing period, and a large day-to-day variability exists within a given month. Ozone amounts for the years 1980 through 1986 combined with a model of radiative transfer provide a climatological baseline against which to interpret the more recent ground-based irradiance data. We focus on monthly mean noontime irradiances integrated over 5 nm wide spectral bands near 305 nm and 340 nm, respectively. Measurements in the 340 nm band show that cloudiness has a large influence on both the absolute monthly mean irradiances and their interannual variability. For example, during December the 340 nm band irradiance varied from approximately 50% of the clear-sky value in 1992 to 65% in 1991. When the influence of cloudiness is removed, most of the months show irradiances in the 305 nm band that are larger than predicted from the climatological ozone amounts. The largest percentage enhancement occurred in October 1991 when the irradiance exceeded the baseline by 56%. The largest absolute irradiances occur in December, where the measurements range from 5.8% below the baseline in 1991 to 31% above in 1990.