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.     

SEASONAL TRENDS IN ERYTHEMAL and CARCINOGENIC ULTRAVIOLET RADIATION AT MID-SOUTHERN LATITUDES1989–1991

A network of solar carcinogenic/erythemal ultraviolet radiometers has been established in New Zealand. Daily integrated irradiances of this biologically harmful ultraviolet radiation for 1989, 1990 and 1991 are reported from radiometers located at Wellington (41°S) and Christchurch (43.5°S) and for 1990 and 1991 from the Auckland (37°S) radiometer. Although the monitoring program has not been running sufficiently long to discern any long-term changes in levels of solar ultraviolet radiation, shorter term trends are apparent, which are attributed to a seasonal cycle in levels of ozone at midlatitudes and changes in atmospheric aerosols.     

Skin Cancer Risks Avoided by the Montreal Protocol—Worldwide Modeling Integrating Coupled Climate‐Chemistry Models with a Risk Model for UV

The assessment model for ultraviolet radiation and risk “AMOUR” is applied to output from two chemistry‐climate models (CCMs). Results from the UK Chemistry and Aerosols CCM are used to quantify the worldwide skin cancer risk avoided by the Montreal Protocol and its amendments: by the year 2030, two million cases of skin cancer have been prevented yearly, which is 14% fewer skin cancer cases per year. In the “World Avoided,” excess skin cancer incidence will continue to grow dramatically after 2030. Results from the CCM E39C‐A are used to estimate skin cancer risk that had already been inevitably committed once ozone depletion was recognized: excess incidence will peak mid 21st century and then recover or even super‐recover at the end of the century. When compared with a “No Depletion” scenario, with ozone undepleted and cloud characteristics as in the 1960s throughout, excess incidence (extra yearly cases skin cancer per million people) of the “Full Compliance with Montreal Protocol” scenario is in the ranges: New Zealand: 100–150, Congo: ?10–0, Patagonia: 20–50, Western Europe: 30–40, China: 90–120, South‐West USA: 80–110, Mediterranean: 90–100 and North‐East Australia: 170–200. This is up to 4% of total local incidence in the Full Compliance scenario in the peak year.     

Sensitivity of erythemally effective UV irradiance and daily exposure to temporal variability in total ozone

The provision of information to the public about current levels of the erythemally effective UV radiation is an important issue in health care. The quality of promoted values is therefore of special importance. The atmospheric parameter which affects the erythemally effective UV radiation under clear sky most is the total ozone content of the atmosphere. In this paper we examined the sensitivity of the erythemally effective irradiance and daily radiant exposure to the temporal variability of total ozone on time scales from 1 to 15 days. The results show that the sensitivity is highest for the first 24 h. Larger time scales do not exhibit a similar influence. Total ozone measurements of the previous day may already cause uncertainties higher than 0.5 UV index (UVI) independent of the geolocation. For comparison, a temporal persistence of 15 days may cause uncertainties of 1.2 UVI at 50°N, 1 UVI at 30°S and less than 1 UVI at the equator. The results of this study allow finding the necessary temporal resolution of total ozone values when a certain accuracy for the UVI or for the purpose of sun protection is required. The results are compared with those of two preceding studies where we quantified the influence of measurement uncertainties and spatial total ozone variability to the erythemally effective irradiance at noon and to the daily dose. We conclude that temporal variability of total ozone is the most critical issue, but also measurement uncertainties do have a noticeable influence on the erythemally effective radiation.     

Evaluation of DNA dosimetry to assess ozone-mediated variability of biologically harmful radiation in Antarctica

In this study we investigated the use of a DNA dosimeter to accurately measure changes in ultraviolet B radiation (UVBR; 280-315 nm) under Antarctic ozone hole conditions. Naked DNA solution in quartz tubes was exposed to ambient solar radiation at Rothera Research Station, Antarctica, between October and December 1998 for 3 h during UVBR peak hours (1200-1500 h). Trends in UVBR-mediated DNA damage (formation of cyclobutane pyrimidine dimers [CPD]) were related to cloud cover, ozone-column depth and spectroradiometric measurements of ambient radiation. Ozone-column depths ranged from 130 to 375 DU during the study period, resulting in highly variable UVBR doses, from 1.6 to 137 kJ m(-2) over the 3 h exposure, as measured by spectroradiometry. There was a strong positive correlation (86%) between dosimeter CPD concentrations and DNA-weighted UVBR doses. Ozone depth was a strong predictor of DNA damage (63%), and there was no significant relationship between CPD formation and cloud cover. Subtle changes in spectral characteristics caused by ozone depletion were detected by the biodosimeter; the highest CPD concentrations were observed in October when ozone-mediated shifts favored shorter wavelengths of UVBR. We conclude that the DNA biodosimeter is an accurate indicator of biologically effective UVBR, even under highly variable ozone conditions.     

Biological monitoring of solar UV radiation at 17 sites in Asia, Europe and South America from 1999 to 2004

A small and robust dosimeter for determining the biologically effective dose of ambient UV radiation has been developed using UV-sensitive mutant spores of Bacillus subtilis strain TKJ6312. A membrane filter with four spots of the spores was snapped to a slide mount. The slide was wrapped and covered with two or more layers of polyethylene sheet to protect the sample from rain and snow and to reduce monthly-cumulative doses within the measurable range. From 1999, monthly data were collected at 17 sites for more than 1 year, and data for 4 to 6 consecutive years were obtained from 12 sites. Yearly total values of the spore inactivation dose (SID) ranged from 3200 at subarctic Oulu to 96000 at tropical Denpasar, and the mean yearly values of SID exhibited an exponential dependence on latitude in both hemispheres with a doubling for about every 14 degrees of change. During the observation period, increasing trends of UV doses have been observed at all sites with more than 5 years of data available. Year-to-year variations at high and middle latitude sites are considered due mostly to climatic variation. At three tropical sites, negative correlations between the yearly doses and the column ozone amounts were observed. The results verified the applicability of spore dosimetry for global and long-time monitoring of solar UV radiation, in particular at tropical sites where no monitoring is taking place.     

BIOLOGICALLY EFFECTIVE DOSES OF SUNLIGHT FOR IMMUNE SUPPRESSION AT VARIOUS LATITUDES AND THEIR RELATIONSHIP TO CHANGES IN STRATOSPHERIC OZONE

Using information on solar irradiance at different latitudes derived from a radiative transfer model and a detailed in vivo action spectrum for immune suppression in a murine system, we report here calculations of the "biologically effective" irradiance of sunlight for immune suppression. From 40 degrees N to 40 degrees S in summer, under normal stratospheric ozone concentrations this value ranged from 0.27 W/m2 (40 degrees N or S) to a peak of 0.33 W/m2 (20 degrees N or S) predicting that 50% immune suppression in the Balb/c mouse would occur after 21-26 min of sunlight exposure within this latitude range. We also found that the most effective wavelengths for immune suppression shift from a peak of 270 nm in the laboratory to near 315 nm in sunlight. Furthermore, using ozone depletion scenarios of 5 to 20%, at latitudes 20 degrees S and 40 degrees N, a 0.6% increase in biologically effective irradiance levels of solar UVB for immune suppression was predicted for each 1% decrease of ozone. This value rose to a nearly 1% increase for each 1% decrease in ozone at 60 degrees N latitude in wintertime. These data indicate that activation of immune suppression, in a murine model, requires relatively low levels of sunlight and that these levels are easily obtainable over most of the populated regions of the world. Since a UVB-activated photoreceptor, urocanic acid, regulates immune suppression in mice and since this same compound exists on other mammalian skin, including human skin, suppression of the mammalian immune system is predicted to increase if substantial stratospheric ozone depletion takes place.     

OZONE DEPLETION AND INCREASE IN ANNUAL CARCINOGENIC ULTRAVIOLET DOSE

An increase in skin cancer incidence due to an increase of solar ultraviolet (UV) radiation is one of the best quantitated effects of stratospheric ozone depletion. Until now, estimates of effective UV dosages could not be based on spectral data on carcinogenicity. Instead the spectral dependence of sunburn or mutations was used. These data contained little information on longwave ultraviolet radiation (UVA: 315-380 nm). Recently, in hairless mice, experimental data have become available on the carcinogenic effectiveness of the ultraviolet, including UVA. From these new data we can estimate the effect of ozone depletion on the ambient annual carcinogenic UV dose. We find that a 1% decrease in ozone yields a 1.56% increase in annual carcinogenic UV; this value is not strongly dependent on geographical latitude. From this result, combined with the dose-response relationship for UV carcinogenesis, we conclude that for a 1% decrease in total column atmospheric ozone an increase of 2.7% in non-melanoma skin cancer is to be expected.     

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.     

大气臭氧化学研究进展

臭氧是大气化学中的核心物种。在平流层中,臭氧层可以吸收对生物有害的紫外辐射,对地球生命起保护伞作用。在对流层大气中,适量臭氧对清洁大气是有益的。但是,由于对流层中臭氧前体物排放量的增加,特别是在大城市,产生的高浓度臭氧会对大气环境造成严重污染,对人类、动植物和生态环境具有极大危害。臭氧的研究一般结合外场观测、实验室烟雾箱模拟和计算机数值模拟进行。深入开展大气臭氧化学研究,不仅有助于全面深入理解大气氧化过程以及全面掌握区域乃至全球大气自净能力,而且能为对流层污染控制提供科学依据和方案。本文总结了近年来有关臭氧化学的研究进展,论述了臭氧问题与人类当前面临的一些主要环境问题间的相互关系;重点综述了近年来有关南极臭氧空洞、中纬度地区臭氧低值和北极地区臭氧的损耗机理及其发展趋势;综述了臭氧与大气光化学和气溶胶间的耦合关系,并结合我国实际情况,提出了大气臭氧化学尚待深入开展研究的一些重要科学问题。     

BIOLOGICALLY EFFECTIVE DOSE OF SOLAR ULTRAVIOLET RADIATION ESTIMATED BY SPORE DOSIMETRY IN TOKYO SINCE 1980

Abstract— The biologically effective dose of solar UV radiation has been measured in Tokyo since 1980 using Bacillus subtills spores. To determine the cumulative dose in a half day, several samples of UV-sensitive spores were exposed in successive intervals from the solar-noon time. Because fluence-survival curves were exponential, the number of lethal hits received by the spores was calculated for each interval and termed inactivation dose (ID). The total number of hits obtained in a half day (half-day ID) was correlated with the amount of global insolation by a power-function regression. The regression analyses were performed for the data collected on 35 days from 1980 to 1986 and for the data collected on 53 days from 1989 to 1991. The latter data set yielded significantly larger estimates of half-day ID relative to the insolation than the former. These analyses suggested that the biologically effective dose relative to the insolation increased about 30% at some time in the later part of 1980s at this location. Changes of solar activity, air pollution and stratospheric ozone layer were considered as potentially responsible for this increase, but identification of the causative factors requires further efforts.     

SOLAR ULTRAVIOLET RADIATION AT THE EARTH'S SURFACE

The biologically effective ultraviolet irradiance at the earth's surface varies with the elevation of the sun, the atmospheric ozone amount, and with the abundance of scatterers and absorbers of natural and anthropogenic origin. Taken alone, the reported decrease in column ozone over the Northern Hemisphere between 1969 and 1986 implies an increase in erythemal irradiance at the ground of four percent or less during summer. However, an increase in tropospheric absorption, arising from polluting gases or particulates over localized areas, could more than offset the predicted enhancement in radiation. Any such extra absorption is likely to be highly regional in nature and does not imply that a decrease in erythemal radiation has occurred on a global basis. The Antarctic 'ozone hole' represents a special case in which a portion of the earth has experienced ultraviolet radiation levels during spring that are far in excess of those which prevailed prior to the present decade.     

Variability of Cloud-free Ultraviolet Dose Rates on Global Scale Due to Modeled Scenarios of Future Ozone Recovery

Simulations of the total ozone content and vertical ozone and temperature profiles during the period 1980–2080 from three chemistry climate models (CCMs) were used and the future variability of five UV dose rate types in global scale was simulated. For each CCM, radiative transfer calculations for cloud-free skies and constant values of aerosol optical properties and surface reflectivity were performed and the percentage difference, relative to the mean over the period 1996–2005, was calculated. The potential biological consequences of ozone recovery are quantified due to the different influence of ozone-absorbing wavelengths on the selected UV action spectra: average percentage differences between a few and 60% are revealed during the 2070s, depending on the latitude zone and the season. Although the research into the prediction of UV radiation levels is ongoing, due to the possible future changes in cloudiness, aerosols or surface reflectivity, the long-term changes in ozone, as projected by the CCMs in a similar way, will affect strongly some of the selected UV dose rates in the future.     

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 column ozone on the variability of biologically effective UV radiation at high southern latitudes

Solar irradiance measurements from Ushuaia (Argentina) and Palmer and McMurdo Stations in Antarctica covering four seasons from mid-1993 through early 1997 have been analyzed and their variations compared with column ozone changes. UV irradiances were weighted for biological effectiveness using a published biological weighting function for dose-dependent inhibition of photosynthesis by phytoplankton from the Weddell Sea. All calculations involved integrated daily UV doses and visible exposures (weighted UV and unweighted visible irradiances, respectively). The results show that daily biologically effective total UV doses underwent large short-term variations at all three sites, with day-to-day increases up to 236% at Ushuaia, 285% at Palmer and 99% at McMurdo. Parallel changes in visible exposure indicated that the total UV changes were preponderantly due to variations in cloudiness. On a 12-month basis, daily biologically effective UV doses correlated strongly with visible exposures (R > or = 0.99). Anticorrelations of total UV with ozone, on the other hand, were poor (R > -0.11). The largest daily biologically effective UV doses, and their day-to-day increases, occurred as part of the normal variability related to cloud cover and were seldom associated with significant ozone depletion. UV dose/visible exposure ratios tended to reflect ozone depletion events somewhat more consistently than UV doses alone. With the Weddell Sea phytoplankton weighting function used in this study, antarctic ozone hole events were seldom readily discernible in the biologically effective UV record. The results suggest that, where the UV sensitivity of organisms was similar to that of the Weddell Sea phytoplankton, seasonal ozone depletion had no appreciable effect on annual primary productivity during the 1993-1997 period. Additional data on the geographical and seasonal variation of biological weighting functions are desirable for more comprehensive assessments of ozone depletion effects at high southern latitudes.     

LONG-TERM VARIATIONS IN ULTRAVIOLET SUNLIGHT REACHING THE BIOSPHERE: . CALCULATIONS FOR THE PAST THREE DECADES

The long-term data base on atmospheric ozone combined with a set of radiative transfer calculations provides estimates of the variability in ultraviolet (UV) sunlight that should have occurred over the period1957–1988 under clear, pollution-free skies. Results refer to the earth's surface at specific locations in the Northern Hemisphere and to averages over collections of sites located in three latitude bands from 30 to 64°N. For any one year the annually integrated solar irradiance, weighted by the action spectrum for erythema, typically lies within3–4% of the 32-year mean. No statistically significant trends span the entire 32-year time frame. However, over the shorter time period1970–1988 the annually integrated erythemal irradiance shows an upward trend of +2.1 ± 1.2% per decade based on all ozone data at latitudes from 40 to 52°N. No trends exist in lower (30-39°N) and higher (53-64°N) latitude bands. We caution that a trend line provides a very simple index of the variability in UV sunlight, and these results should not necessarily be extrapolated into the future.     

Daily duration of vitamin D synthesis in human skin with relation to latitude, total ozone, altitude, ground cover, aerosols and cloud thickness

Vitamin D production in human skin occurs only when incident UV radiation exceeds a certain threshold. From simulations of UV irradiances worldwide and throughout the year, we have studied the dependency of the extent and duration of cutaneous vitamin D production in terms of latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude. For clear atmospheric conditions, no cutaneous vitamin D production occurs at 51 degrees latitude and higher during some periods of the year. At 70 degrees latitude, vitamin D synthesis can be absent for 5 months. Clouds, aerosols and thick ozone events reduce the duration of vitamin D synthesis considerably, and can suppress vitamin D synthesis completely even at the equator. A web page allowing the computation of the duration of cutaneous vitamin D production worldwide throughout the year, for various atmospheric and surface conditions, is available on the Internet at http://zardoz.nilu.no/~olaeng/fastrt/VitD.html and http://zardoz.nilu.no/~olaeng/fastrt/VitD-ez.html. The computational methodology is outlined here.     

OZONE AND ULTRAVIOLET-B IRRADIANCES: EXPERIMENTAL DETERMINATION OF THE RADIATION AMPLIFICATION FACTOR

Abstract— During the period 1981–1993, measurements of solar UV irradiances were made at the High-Alpine Research Station Jungfraujoch (Switzerland, 3576 m a.s.l.) to determine the radiation amplification factor (RAF) for the Robertson-Berger sunburn meter and for the narrow-band wavelength ranges of the Eppley filter spectrometer. The Robertson-Berger sunburn meter model 500 showed a RAF of 1.07 ± 0.15 at solar elevations between 20° and 60°. The RAF for human erythema is 1.1 in comparison. Therefore the Robertson-Berger sunburn meter is suitable to measure the influence of total atmospheric ozone variations on the effective erythemal irradiance. In the narrow-band wavelength ranges of the Eppley filter spectrometer the RAF increases greatly at shorter wavelengths with RAF of 1.06, 1.40 and 2.35 for the optical centers 315.1 nm, 311.1 nm and 305.2 nm, evaluated at 30° solar elevation. In order to minimize perturbations by aerosol optical depth and albedo in the evaluation of the RAF the ratios of UV irradiances to total irradiances were evaluated.     

Erythemal Ultraviolet Insolation in New Zealand at Solar Zenith Angles of 30° and 45°

Solar UV radiometers with spectral responsivities that are close to the erythemaVcarcinogenic action spectrum of skin have been installed at several centers of population in New Zealand, including Auckland, 37°S, Wellington, 41°s and Christchurch, 43.5°S. The data set covers the period from the time the radiometry program commenced in 1988/1989 to the end of the southern summer, March 1995. The radiometers were recalibrated annually and the data were corrected for changes in the absolute responsivity of the radiometers. Erythemally effective UV irradiances at solar zenith angles of 30° and 45° were then extracted from the data set. No monotonic trend in these data is apparent, although there are statistically significant differences in mean irradiances from one year to the next. An example of this is the decrease observed in all sites following the Mt. Pinatubo eruption in June 1991. The maximum erythemally effective insolations at solar zenith angles of 30° and 45° were consistently lower in Christchurch than in the other two New Zealand sites. This could arise from higher levels of atmospheric turbidity andlor tropospheric ozone at this location. Also, a seasonal increase in erythemally effective UV insolation from spring to autumn was observed each year in all three New Zealand sites.     

UV-B exposure causes DNA damage and changes in protein expression in northern pike (Esox lucius) posthatched embryos

The ongoing anthropogenically caused ozone depletion and climate change has increased the amount of biologically harmful UV-B radiation, which is detrimental to fish in embryonal stages. The effects of UV-B radiation on the levels and locations of DNA damage manifested as cyclobutane pyrimidine dimers (CPDs), heat shock protein 70 (HSP70) and p53 protein in newly hatched embryos of pike were examined. Pike larvae were exposed in the laboratory to current and enhanced doses of UV-B radiation. UV-B exposure caused the formation of CPDs in a fluence rate-dependent manner, and the CPDs were found deeper in the tissues with increasing fluence rates. UV-B radiation induced HSP70 in epidermis, and caused plausible p53 activation in the brain and epidermis of some individuals. Also at a fluence rate occurring in nature, the DNA damage in the brain and eyes of pike and changes in protein expression were followed by severe behavioral disorders, suggesting that neural molecular changes were associated with functional consequences.