BIOLOGICAL UV-DOSES AND THE EFFECT OF AN OZONE LAYER DEPLETION

Effective UV-doses were calculated based on the integrated product of the biological action spectrum (the one proposed by IEC, which extends to 400 nm, was adopted) and the spectral irradiance. The calculations include absorption and scattering of UV-radiation in the atmosphere, both for normal ozone conditions as well as for a depleted ozone layer. For Scandinavian latitudes the effective annual UV-dose increases by approximately 4% per degrees of latitude towards the Equator. An ozone depletion of one percent increases the annual UV-dose by approximately 1% at 60 degrees N (increases slightly at lower latitudes). A large depletion of 50% over Scandinavia (60 degrees N) would give these countries an effective UV-dose similar to that obtained, with normal ozone conditions, at a latitude of 40 degrees N (California or the Mediterranean countries). The Antarctic ozone hole increases the annual UV-dose by 20 to 25% which is a similar increase as that attained by moving 5 to 6 degrees of latitude nearer the Equator. The annual UV-dose at higher latitudes is mainly determined by the summer values of ozone. Both the ozone values and the effective UV-doses vary from one year to another (within +/- 4%). No positive or negative trend is observed for Scandinavia from 1978 to 1988.     

PROJECTIONS OF INCREASED NON-MELANOMA SKIN CANCER INCIDENCE DUE TO OZONE DEPLETION

Abstract— Projections of increase in non-melanoma skin cancer incidence due to ozone layer depletion by chlorofluorocarbons are presented. Projections have been made for five different ozone depletion scenarios, based on US. Environmental Protection Agency estimates of potential worldwide industrial production and commercial applications of chlorofluorocarbons, and their eventual release into the atmosphere. The least favorable scenario, a regulatory cap on production at estimated 1990 levels, would lead to an eventual 30% ozone depletion and to an eventual doubling of skin cancer incidence by the year 2300. The most favorable scenario, a reduction in production commencing now and reaching a low production target by 1990, would limit ozone depletion to an eventual 2.8%, and increase in skin cancer to about 5%. Compared to the least favorable scenario, the most favorable one would prevent an average of about 100,000 cases of skin cancer per year in the United States between now and the year 2100.     

STRATOSPHERIC OZONE DEPLETION BETWEEN 1979 and 1992: IMPLICATIONS FOR BIOLOGICALLY ACTIVE ULTRAVIOLET-B RADIATION and NON-MELANOMA SKIN CANCER INCIDENCE

Abstract— The depletion of stratospheric ozone (0₃) has predictable implications for increases in biologically damaging solar ultraviolet-B radiation (UVB,280–320 nm) reaching the earth's surface. A radiative transfer analysis of satellite-based O₃ measurements between January 1979 and December 1992 shows that surface UVB levels increased substantially at all latitudes except the tropics, if other factors such as cloud cover and local pollutant levels have remained constant over this period. Exposure to UVB radiation is known to induce basal cell and squamous cell skin cancers, and dose-response relationships derived from epidemiological data can be combined with the UVB enhancements to estimate the seasonal and latitudinal distribution of future expected increases in the incidence of these cancers.     

EFFECTS OF ARCTIC OZONE DEPLETION AND SNOW ON UV EXPOSURE IN FINLAND

The increase in the UV exposure of the Finnish population associated with the combined effects of ozone depletion and snow reflection was studied with the aid of theoretical calculations based on Green's clear sky UV model. A simple formula was utilized to transform horizontal irradiances to vertical irradiances averaged over 360 azimuth angle. The model was verified with spectral and broadband measurements. The difference between the theoretical and measured UV radiation falling to horizontal surfaces was in most cases less than ±10%, and the additional error to theoretical vertical irradiances was less than ± 10%. The calculations show that the annual horizontal doses in Helsinki (60.2°N, 25°E) are about 35% higher than in Saariselkä (68.4°N, 27.5°E), but the difference is only 16% for vertical doses owing to the stronger contribution to vertical (facial) surfaces of the reflection of UV from snow. At Saariselkä, the maximum vertical irradiance at the end of April approaches the midsummer values. The ozone depletions up to 40% in February and March 1992 had no significant effect on the annual doses because the total ozone returned to normal before the UV increased to biologically significant levels.     

CAROTENOIDS AFFECT DEVELOPMENT OF UV-B INDUCED SKIN CANCER

One large dose of UV-B (8 × 10¹⁴ J m^-2: 290-320 nm) has been found to cause the development of skin tumors in hairless mice, and carotenoid pigments prevent or delay tumor development in this system. This model was used to determine if the protective effect of carotenoid pigments against UV-B induced skin tumors occurred during the induction phase or progression phase of UV-B carcinogenesis. The results indicate that the carotenoids canthaxanthin and (J-carotene interfered with the progression phase in this system; whether they also had an effect during induction could not be definitely determined from our data.     

ANNUAL EXPOSURES TO CARCINOGENIC RADIATION FROM THE SUN AT DIFFERENT LATITUDES and AMPLIFICATION FACTORS RELATED TO OZONE DEPLETION. THE USE OF DIFFERENT GEOMETRICAL REPRESENTATIONS OF THE SKIN SURFACE RECEIVING THE ULTRAVIOLET RADIATION

In most calculations of annual fluences of carcinogenic light as well as of the radiation amplification factor and of biological amplification factors associated with ozone depletions, the radiation is assumed to fall on a horizontally oriented plane surface. This is obviously a bad approximation of the surface of the human body. In order to evaluate the importance of using a realistic geometric representation of the surface of the human body we here present calculations of the flux of carcinogenically effective radiation falling on three different bodies: a vertically standing cylinder, a sphere and a horizontally oriented surface. The exposure to carcinogenic radiation depends strongly on the surface geometry. However we find that the radiation amplification factors are almost independent of the surface geometry chosen. The biological amplification factors for the three geometrical representations are also similar to within 20%. The total amplification factor for the increase in the incidence of non-melanoma skin cancer related to ozone depletion is about 17% larger when a cylindrical representation is used compared to when a plane horizontal surface is considered.     

THE ULTRAVIOLET DOSE DEPENDENCE OF NON-MELANOMA SKIN CANCER INCIDENCE

Abstract— We correlate annual ultraviolet dose estimates with age specific and age adjusted incidence data for non-melanoma skin cancer in the United States, United Kingdom, Canada and Australia. We first examine (1) a reciprocity or photographic model in which incidence rates (R) are related to exposure (E) which is the product of age (T) and annual dose (D). We also test several models which violate reciprocity including models identified by the labels: (2) Dose potency; (3) Double cause; (4) Age-exposure and (5) separable. Our analyses together with the recent National Cancer Institute study favors the age-exposure model and/or the double cause models. All models lead to biological amplification factors (defined as the ratio of the percent increase in skin cancer incidence due to a 1% increase in dose) greater than unity. For the U.S. we find the biological amplification to be approximately 1.8 for the population center but greater in regions of higher UV annual dose, and less in regions of lower annual UV dose.     

EFFECT OF POLYAMINE DEPLETION ON DNA DAMAGE and REPAIR FOLLOWING UV IRRADIATION OF HeLa CELLS

Treatment of HeLa cells with the polyamine biosynthesis inhibitors, methylglyoxal bis(guanylhydrazone) (MGBG), difluoromethylornithine (DFMO) or a combination of the two, resulted in reduction in cellular polyamine levels. Analysis of UV light-induced DNA damage and repair in these polyamine depleted cells revealed distinct differences in the repair process relative to that seen in cells possessing a normal polyamine complement. Initial yield of thymine dimers and rate of removal of these lesions from cellular DNA appeared normal in polyamine-depleted cells. However, depleted cells exhibited retarded sealing of DNA strand breaks resulting from cellular repair processes, reduced repair synthesis and an increased sensitivity to UV killing. Incision at damaged sites was not affected since ara-C repair-dependent breaks accumulated in a normal fashion. Molecular analysis of inhibited repair sites by exonuclease III and T4 DNA ligase probes suggest that the strand interruptions consist of gaps rather than ligatable nicks, consistent with an interpretation of the repair defect being at the gap-filling stage rather than the ligation step. Observed patterns of differential polyamine depletion by DFMO and MGBG, and partial reversal of repair inhibition by polyamine supplementation, suggests that polyamine depletion per se, rather than some secondary effect of inhibitor treatment, is responsible for the inhibition of repair.     

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.     

CALCULATION OF THE YOUNG''''S MODULUS OF AN ADSORBED POLYMER LAYER

Polymer layers adsorbed to a surface or in a confined environment often change their mechanical properties. There is even the possibility of solidification of the confined layer. To judge the stiffness of such a layer, we used the Hertz model to calculate the Young's modulus of the polymer layer in the confinement of AFM experiments with silicon nitride tip with a radius of curvature of R≈50 nm and a glass sphere attached to the cantilever R = 5μm. Since there is no visible indentation of the layer in the AFM experiments, the layer is either penetrated very easily, or the indentation is too small to be seen in a force curve. The latter would be the case for a polymer layer with a Young's modulus above 4×108 Pa in case of an experiment with a silicon nitride tip and 4×105 Pa in case of a glass sphere.     

制膜液黏度对单皮层PVDF中空纤维膜纺制的影响

以二甲基乙酰胺(DMAc)为溶剂,制备聚偏氟乙烯(PVDF)浓度为15%的制膜液,考察了DMAc同时作为内凝胶浴时膜结构的变化.为保持纺膜过程中的稳定性,分别考察了添加剂LiCl、水以及表面活性剂对制膜液黏度的影响.实验发现添加LiCl可以大大提高制膜液的黏度,而水作为添加剂时对黏度的影响与制膜液本身的浓度有关.在不提高制膜液浓度的基础上,通过提高制膜液黏度克服了膜在纺制过程中的不稳定问题,得到阻力较小的,指状孔贯穿的单外皮层中空纤维膜.     

ENHANCEMENT OF MUTAGENESIS AND HUMAN SKIN CANCER RATES RESULTING FROM INCREASED FLUENCES OF SOLAR ULTRAVIOLET RADIATION

Abstract— We present a new method for calculating the effects of reduction of atmospheric ozone upon induction of nonmelanoma skin cancer. These estimates are based upon several recent experimental improvements: a model for the atmospheric penetration of UV-B; measurements of the transmission of this radiation by human epidermis; a precise action spectrum for genetic effects (mutation) in Escherichia coli , which was corrected for finite slit width. The calculated radiation amplification factor or percent increase in exposure per one percent decrease in atmospheric ozone is constant at 1.7 for solar zenith angles = 70° and decreases only with larger values of this angle. Thus the estimated increase applies to all heavily populated areas. of the globe. The value is robust: it is almost the same when the albedo is reduced from 0.2 to 0.1 or when the epidermal transmission is assumed to be about fourfold greater.     

EFFECT OF IONIZING RADIATION UPON TOTAL DIFFUSE SPECTRAL REFLECTANCE OF ULTRAVIOLET LIGHT BY SKIN

Abstract— Irradiation of guinea-pig skin with X rays and beta particles resulted in decreased total diffuse reflectance (DSR) of 330–400 nm light. Qualitatively, this response resembled that seen after irradiation of the skin of normal guinea-pigs with ultraviolet (UV) radiation of wavelength shorter than 300 nm or that of photosensitized guinea pigs with UV wavelengths longer than 300 nm. We postulate that the transformations which depress the DSR result from energy-transfer processes, independent of the class of radiation. Moreover, they are intimately related to subsequent changes in vascular permeabilities (delayed erythema) which occur after the same radiation exposures that lower the 330–400 nm DSR of skin surfaces.     

聚酰胺表面结构及其对复合膜分离性能的影响

以杂萘联苯聚芳醚超滤膜为支撑层,通过间苯二胺(MPD)、哌嗪(PIP)与均苯三甲酰氯(TMC)的界面聚合制备复合膜.用红外光谱和X射线衍射分别分析了超薄功能层的化学结构与聚集态,用原子力显微镜观察了膜表面形貌,并用统计学方法计算了膜表面的平均粗糙度等特性参数,研究了MPD/PIP比例对膜表层化学结构、形貌和分离性能的影响.结果表明,随着二胺单体MPD/PIP比例从0/100提高到100/0,功能层聚酰胺的聚集态具有从无定形向部分结晶转变的趋势,复合膜表面平均粗糙度由17.8nm提高到71.9nm,膜对NaCl的截留率由26%提高到99%,而通量则由130L.m-2.h-1降低到12L.m-2.h-1.复合膜具有良好的稳定性,温度由25℃提高到80℃,通量提高了2倍左右,而对NaCl的截留率基本不变.     

PROTECTIVE EFFECT OF SELENIUM AND ZINC ON UV-A DAMAGE IN HUMAN SKIN FIBROBLASTS

Ultraviolet A radiation participates in cytotoxicity and carcinogenesis of the skin by a mechanism involving the generation of reactive oxygen species. Endogenous antiradical defense systems utilize metalloenzymes including Se-dependent glutathione peroxidase and Cu and Zn superoxide dismutase. The aim of the present work was to determine the protective effect of two trace elements, Se and Zn, on cultured human diploid fibroblasts exposed to UV-A radiation (broad-spectrum source with a maximum intensity at 375 nm). Selenium in the culture medium (0.1 mg/L) in the form of sodium selenite increased the synthesis and activity of glutathione peroxidase by 60.5% in the absence of exposure to UV-A radiation and by 35% after irradiation with 5 J/cm² ( P = 0.043). The presence of this element significantly increased the survival of UV-A-irradiated fibroblasts ( P < 0.0001). This confirms the essential role of Se in the detoxifying activity of the enzyme. In addition, thiobarbituric acid-reacting substances (TBAR), which are lipid peroxidation markers, decreased in the presence of exogenous Se:—19% and -22% without irradiation and after irradiation with 5 J/cm² ( P = 0.056). When Zn was added at the dose of 6.5 mg/L as ZnCl₂, fibroblasts subjected to oxidizing stress induced by UV-A were protected from cytotoxicity ( P <0.0001). The TBAR production decreased significantly: -33% without irradiation and -34% after irradiation with 5 J/cm² ( P = 0.008). Superoxide dismutase activity, however, decreased after supplementing with Zn: - 26% without irradiation and - 20% after UV-A irradiation ( P = 0.017). The antioxidant properties of Zn are thus apparently independent of superoxide dismutase activity.     

EFFECT OF CHRONIC UV EXPOSURE ON EPIDERMAL FORWARD SCATTERING-ABSORPTION INSK–1 HAIRLESS MOUSE SKIN

Abstract— Clinical and histological precancerous responses to UV irradiation are complicated dynamic functions of total dose, dose fractionation, fluence rate, and spectral distribution. This may be due, in large part, to the ability of UV to decrease epidermal-stratum corneum transmission by stimulation of hyperplasia. This work provides quantitative measurement of dose- and wavelength-dependent optical changes inSK–1 hairless mouse epidermis-stratum corneum occurring under irradiation with “monochromatic” UV wavebands, at 280, 290, 300, 307, and 313 nm. Mice were irradiated 5 days per week with a filtered Xenon-Hg high-intensity grating monochromator, starting with 0.9 minimal erythemal dose (MED), followed by incremental increases in the radiation dose by 20% of the original dose every tenth irradiation day, for2–8 consecutive weeks. Subsequent irradiations (for longer experiments) were followed by 30% incremental increases after the 8th week every 10th irradiation day until cessation of radiation at the end of 14 weeks. Irradiated and control full-thickness epidermis/ stratum corneum were examined histologically and by forward-scattering absorption spectroscopy. Chronic irradiation of hairless mice resulted in significant hyperplasia which was optically manifested by a general increase in forward-scattering absorbance. At moderate local doses (7.2 MED), the absorbance increase per MED was approximately the same for all excitation wavelengths, whereas at large total doses (? 100 MED) the optical increase per delivered MED progressively decreased in the order 313> 307> 300? 290> 280 nm. The increase in skin thickening, expressed as observed increase in absorption at 320 nm, correlated well with histological and clinical data. We propose that optical changes induced by UV-induced thickening can account in large part, if not entirely, for dynamic changes in action spectra for (pre) cancerous processes under chronic irradiation conditions.     

THE EFFECT OF LIGHT ON THE OCELLAR PIGMENT OF SPIROCODON, AN ANTHOMEDUSA

Abstract— The ocellar pigment of Spirocodon saltatrix was extracted with 2% mildly alkaline cetyltrimethylammonium bromide (CTAB) and 90% methanol acidified with HCl. In the case of CTAB-extracted pigment, maximum changes in optical density upon illumination occurred in mildly alkaline media under aerobic conditions and in neutral media under anaerobic conditions. The density spectrum of the sample illuminated under anaerobic conditions closely resembled that of the reduced form of the pigment illuminated in the presence of air. When reduced in darkness, the pigment became photostable and its density spectrum differed from that of the pigment reduced after illumination. On aeration of the pigment solution illuminated under anaerobic conditions, its density spectrum in the visible range became similar to that of the pigment illuminated in the presence of air. A trace of air dissolved in experimental media caused auto-oxidation of the reduced form, during the process of which a definite isosbestic point was observed at 480 mμ. Under anaerobic conditions, short period of illumination produced changes in spectral absorbance only in the visible range. Changes in the u.v. range required longer exposures. The pigment extracted with acidified methanol was readily auto-oxidizable and it was the reduced form which showed photosensitivity, though the degree of sensitivity was extremely low. The density spectrum of illuminated pigment resembled that of the oxidized form. From these experiments, a tentative scheme involving an electron transfer system has been suggested for the chain of photic reaction of the anthomedusan ocellar pigment.