A Model-Derived Global Climatology of UV Irradiation at the Earth's Surface

Abstract— We present calculations of the geographical distribution of the dose rate at the surface of UVB (280–320 nm), UVA (320–400 nm) and, using biological action spectra, the effective radiation for erythema, cataracts and keratitis. A multistream radiative transfer model is used in conjunction with a multiyear climatology of ozone, cloud, surface pressure, surface albedo, temperature and a rudimentary representation of aerosols to calculate the clear-sky and all-sky irradiances. Model outputs are evaluated using daily UV measurements and found to be accurate to about ±10% for clear skies and ±20% for all-sky conditions. The effects of UV-weighted surface albedo, surface altitude, sun-earth separation and the vertical distribution of ozone and temperature are included. The results show that the sun's position is the most important factor in determining the geographical pattern of global daily UV rather than column ozone, cloud, surface pressure, daylength or surface albedo. Over elevated regions, the effect of the differences in surface pressure on daily doses was found to be more significant than the effect of the differences in column ozone. Clouds reduce the clear-sky UV dose from a few percent over arid and semiarid regions to 45% in regions with frequent midlatitude depressions.     

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.     

Future UV radiation in Central Europe modelled from ozone scenarios

Photobiologically and photochemically relevant UV radiation for the time around the years 2015 and 2050 is estimated by radiative transfer calculations using variable ozone content based on model simulations. The future cloud conditions are assumed unchanged. Assuming various emission scenarios of chlorfluorohydrocarbons (CFCs) and other trace gases, and taking into account future temperature development and changing atmospheric dynamic conditions, ozone values are simulated. On the basis of these data, three different scenarios of the future total ozone content over Central Europe are analysed, which represent from current knowledge, probable as well as optimistic (high ozone and low UV irradiance) and pessimistic (low ozone and high UV irradiance) conditions. According to these scenarios the future development of the UV radiation is expected not to follow the increasing trend of UV irradiation observed during the last three decades. The predicted changes are highly variable with season. During late winter and spring, the enhanced recent UV values will persist for the next decades. Till 2015 a further slight increase is predicted for springtime. In contrast, during summer and fall, the UV level is assumed to remain on the recent level. For 2050 a decrease to values close to that of an anthropogeneous nearly undisturbed ozone chemistry, as it was found around 1970, is predicted. In addition to average long-time variations of the UV irradiance, short-time increase may occur due to ozone minihole events or due to a large volcanic eruption. The latter can produce a marked increase in UV radiation for several months. During ozone minihole events, with maximum occurrence in spring, UV irradiance is typically increased for a few days. Such episodes must be taken into account additionally to the average UV development. They will occur also in the future and result in UV radiation increases against undisturbed conditions, which are similar to present minihole events. These differences are much larger than the average changes predicted for future ozone development.     

MULTIPLE EFFECTS OF UV RADIATION (265–330 NM) ON FUNGAL SPORE EMERGENCE

We have investigated the influence of narrow-band UV radiation, 265–330 nm. on germination of spores of the fungus Cladosporium cucumerinum Ellis and Arth., using a Xe arc lamp and filters. Reciprocity of time and dose rate was demonstrated when fungal spores were subjected to UV radiation at 325 nm but failed to hold at 265 nm. Based on these findings, data on fluence response, and partial action spectra, we propose that there are two biologically active sites in this organism that are affected by radiation between 265 and 330 nm and that might be influenced by changes in the stratospheric ozone layer: a short-wave-sensitive site (265–295 nm) and a long-wave-sensitive site (300–330 nm). Data obtained with narrow-band interference filters confirmed previous reports of damage to nucleic acid from UV at 265–295 nm and in addition demonstrated significant inhibition by UV at 300–320 nm. Further studies of the 300 330 nm portion of the spectrum, using combinations of plastic and glass filters, showed that the influence of UV radiation in this region was primarily to produce a non-photoreactivable delay in germ-tube emergence.     

Surface modification of Sylgard-184 poly(dimethyl siloxane) networks by ultraviolet and ultraviolet/ozone treatment

We report on the surface modification of Sylgard-184 poly(dimethyl siloxane) (PDMS) networks by ultraviolet (UV) radiation and ultraviolet/ozone (UVO) treatment. The effects of the UV light wavelength and ambient conditions on the surface properties of Sylgard-184 are probed using a battery of experimental probes, including static contact angle measurements, Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups. The radicals formed during this process recombine and form a network whose wetting properties are similar to those of a UV-modified model PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and near-surface structure of Sylgard-184. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified specimen. As a result of these interactions, the surface of the sample contains a large number of hydrophilic (mainly -OH) groups. In addition, the material density within the first approximately 5 nm reaches about 50% of that of pure silica. A major conclusion that can be drawn from the results and analysis described in this work is that the presence of the silica fillers in Sylgard-184 does not alter the surface properties of the UVO- and UV-modified Sylgard-184.     

Reconstruction of Solar Spectral Surface UV Irradiances Using Radiative Transfer Simulations

UV radiation exerts several effects concerning life on Earth, and spectral information on the prevailing UV radiation conditions is needed in order to study each of these effects. In this paper, we present a method for reconstruction of solar spectral UV irradiances at the Earth's surface. The method, which is a further development of an earlier published method for reconstruction of erythemally weighted UV, relies on radiative transfer simulations, and takes as input (1) the effective cloud optical depth as inferred from pyranometer measurements of global radiation (300–3000 nm); (2) the total ozone column; (3) the surface albedo as estimated from measurements of snow depth; (4) the total water vapor column; and (5) the altitude of the location. Reconstructed daily cumulative spectral irradiances at Jokioinen and Sodankylä in Finland are, in general, in good agreement with measurements. The mean percentage difference, for instance, is mostly within ±8%, and the root mean square of the percentage difference is around 10% or below for wavelengths over 310 nm and daily minimum solar zenith angles (SZA) less than 70°. In this study, we used pseudospherical radiative transfer simulations, which were shown to improve the performance of our method under large SZA (low Sun).     

PHOTOINHIBITION OF PHOTOSYNTHESIS IN NATURAL WATERS*

Abstract— A quantitative analysis of the wavelength-dependent influence of solar irradiance on natural phytoplankton photosynthesis has been made. The effect on productivity due to several different UV radiation regimes has been measured. In the course of this analysis, it has been shown that the biological weighting function for photoinhibition of chloroplasts (Jones and Kok, 1966) allows the calculation of a biologically effective dose which is consistent with the measured photoinhibition in natural phytoplankton populations. The ecological implications of a change in available UV radiation, possibly due to anthropogenic altering of the ozone layer, are explored and it is found that the present static bottle ^l4C technique of measuring in situ phytoplankton productivity does not lend itself to assessing accurately the potential ecological consequences of possible increased MUV (middle ultraviolet radiation in the 280–340 nm region) on phytoplankton populations. A small change in MUV has a relatively minor effect on photoinhibition dose rates whereas it has a large potential effect on DNA dose rates.     

A NEW DOSIMETER FOR ULTRAVIOLET-B RADIATION

Abstract— A type of polycarbonate plastic was found to be sensitive to ultraviolet (UV) radiation. The damage to the material due to UV exposure was revealed by etching in a strong alkaline solution. The latent effect can be retained in the material for a period of at least 30 days. The material was tested for use as a detector of ultraviolet-B (UV-B 280–320 nm) radiation.
The response of the detector in the wavelength region between 254 and 365 nm was determined using a set of narrow-band filters and a 200 W UV xenon-mercury lamp. The maximum UV effect in the detector was observed at a wavelength of 290 nm. The spectral response curve was found to be similar to the human erythema action spectrum.
The detector may be miniaturized for dosimetric applications. The dose response curve is linear in the region up to an erythemal dose of 300 mJcm⁻². Laboratory and field tests showed that the dosimeter response to UV exposure was additive and was independent of dose rate. Further experiments suggested that the dosimeter was stable against changes in temperature and humidity.     

Study of ultraviolet light and ozone surface modification of polypropylene

Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combinations of ultraviolet light and ozone gas (UVO) conditions were studied. Exposure of the polymer surface was carried out in a laboratory-scale UVO reactor in which the following parameters could be varied: ozone concentration, wavelength of ultraviolet (UV) radiation, pulsed operation of the UV lamps, the treatment distance between the PP film and the lamps, and water vapor concentration. Advancing and receding contact angle measurements were used to monitor surface energy changes imparted by the treatment. Two spectroscopic techniques, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR), were used to monitor changes in the polymer surface chemistry. Oxidation of the PP surface is proposed to occur through two alternate mechanisms: (1) insertion of an O (¹D) atom to form ether linkages, or (2) hydrogen abstraction by O (³P), followed either by crosslinking or by reaction with oxygen species to form carbonyl and/or carboxyl functional groups. It was found that reaction 1 dominates initially, but that its rate is reduced by the formation of products from reaction 2. It appears that the ether functional groups produced by reaction 1 are responsible primarily for increased surface energy. Carbonyl, carboxyl, and hydroxyl groups formed in reaction 2 appear to have little additional effect on surface energy; it is proposed that these groups are involved strongly in intramolecular hydrogen bonding, thereby decreasing their availability to contribute to increased surface energy. High-energy UV radiation was found to play only a minor role in the surface modification of PP. Of the narrow range of ozone concentrations studied, no clear relationship was found to exist between ozone concentration and rate of modification of the surface; thus, the concentration of ozone must not affect the relative concentrations of products from the competing reactions. Increased surface oxidation and decreased contact angles were observed when the lamp-to-sample distance was minimized. The presence of water vapor during UVO treatment was found to lead to greater oxygen uptake after short-term treatments but did not result in increased surface energy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2489–2501, 1999     

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%.     

Use of Uracil Thin Layer for Measuring Biologically Effective UV Dose

Abstract— Dimerization of uracil monomers in a polycrystalline state by UV radiation changes the absorption characteristics of a thin layer of the material. The change in optical density, measured by spectrophotometry in the250–400 nm range, as a function of the exposure time is evaluated in terms of the biologically effective UV dose. A statistical evaluation of a great number of uracil dosimeters irradiated with a TL01 lamp from Philips establishes the possibility of evaluating the biologically effective UV dose using a uracil dosimeter. Nonlinear regression procedures were introduced to correct the absorption spectra for contributions due to light scattering and to determine the optical density values required to calculate the UV dose expressed in H^Uunits. Comparison of cumulative daily doses and long-term monitoring measured by the uracil thin-layer dosimeter and a phage T7 dosimeter are given, which allow the determination of conversion factors between various biological dosimeters under different irradiation conditions.     

Reflected solar radiation from horizontal, vertical and inclined surfaces: ultraviolet and visible spectral and broadband behaviour due to solar zenith angle, orientation and surface type

Ultraviolet (UV) radiation affects human life and UV exposure is a significant everyday factor that individuals must be aware of to ensure minimal damaging biological effects to themselves. UV exposure is affected by many complex factors. Albedo is one factor, involving reflection from flat surfaces. Albedo is defined as the ratio of reflected (upwelling) irradiance to incident (downwelling) irradiance and is generally accepted only for horizontal surfaces. Incident irradiance on a non horizontal surface from a variety of incident angles may cause the reflectivity to change. Assumptions about the reflectivity of a vertical surface are frequently made for a variety of purposes but are rarely quantified. As urban structures are dominated by vertical surfaces, using albedo to estimate influence on UV exposure is limiting when incident (downwelling) irradiance is not normal to the surface. Changes to the incident angle are affected by the solar zenith angle, surface position and orientation and surface type. A new characteristic describing reflection from a surface has been used in this research. The ratio of reflected irradiance (from any surface position of vertical, horizontal or inclined) to global (or downwelling) irradiance (RRG) has been calculated for a variety of metal building surfaces in winter time in the southern hemisphere for both the UV and visible radiation spectrum, with special attention to RRG in the UV spectrum. The results show that the RRG due to a vertical surface can exceed the RRG due to a horizontal surface, at smaller solar zenith angles as well as large solar zenith angles. The RRG shows variability in reflective capacities of surface according to the above mentioned factors and present a more realistic influence on UV exposure than albedo for future investigations. Errors in measuring the RRG at large solar zenith angles are explored, which equally highlights the errors in albedo measurement at large solar zenith angles.     

Ultraviolet Radiation at Sites on the Antarctic Coast

Ground-based measurements of solar UV irradiance combined with calculations using satellite-based ozone data are able to define the variability in UV sunlight at Palmer Station and McMurdo Station, Antarctica over time scales of years. Special attention focuses on the spring and summer seasons. Satellite data show that the annual ozone loss that occurs during October was greater in1991–1992 than in1979–1980. This led to average noontime UVB irradiances computed for clear skies in the latter period that exceeded those in the earlier time by50–65%. However, a biologically weighted irradiance for suppression of photosynthesis in phytoplankton indigenous to the area near McMurdo Station increased by at most 5% over this period in response to the change in ozone owing to an important contribution from the UVA. At Palmer Station the behavior of ozone and cloudiness can mesh so as to produce the largest noontime UVB irradiances of the year in October as opposed to near summer solstice in December and January. Interannual variability in UVB irradiance during October, the month of the major ozone loss, is larger at Palmer than at McMurdo during the time spanned by ground-based irradiance measurements, being1990–1994. However, interannual variations in cloudiness were more important than changes in ozone in causing the observed year-to-year variability at Palmer Station. The opposite situation prevailed at McMurdo during October, where interannual variations in ozone were responsible for most of the year-to-year differences in UVB received at the ground.     

Investigating the interface of superhydrophobic surfaces in contact with water

Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160 degrees (superhydrophobic) to <10 degrees (hydrophilic). NR shows that the superhydrophobic nature of the surface prevents infiltration of water into the porous film. Atomic force microscopy and density functional theory simulations are used in combination to interpret the NR results and help establish the location, width, and nature of the SH film-water interface.     

The role of the spectral sensitivity curve in the selection of relevant biological dosimeters for solar UV monitoring

To estimate the risk of enhanced UV-B radiation due to stratospheric ozone depletion, phage T7 and uracil thin-layer biological dosimeters have been developed, which weight the UV irradiance according to induced DNA damage. To study the molecular basis of the biological effects observed after UV irradiation, the spectral sensitivity curves of the two dosimeters and induction of the two major DNA photoproducts, cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts ((6-4)PDs), in phage T7 have been determined for polychromatic UV sources. CPDs and (6-4)PDs are determined by lesion-specific monoclonal antibodies in an immunodotblot assay. Phage T7 and uracil biological dosimeters together with a Robertson-Berger (RB) meter have been used for monitoring environmental radiation from the polar region to the equator. The biologically effective dose (BED) established with the three different dosimeters increases according to the changes in the solar angle and ozone column, but the degree of the change differs significantly. The results can be explained based on the different spectral sensitivities of the dosimeters. A possible method for determining the trend of the increase in the biological risk due to ozone depletion is suggested.     

Short-term UV exposure of sunbathers at a Mediterranean Sea site

The aim of this study was to investigate whether systematic differences in solar UV exposure on a specific anatomical site (chest) exist among three groups of Italian sunbathers: healthy subjects (suntanned and non-suntanned individuals) and subjects affected by abnormally high sensitivity to solar exposure. A second aim of the study was to search for a possible relation among biological markers of individual response to UV exposure (such as skin colorimetric parameters, skin temperature and changes in free radical amounts [FR] in the blood) and photosensitivity. FR in the blood were analyzed because of their possible influence on UV carcinogenesis. Measurements of ambient doses (i.e. incident erythemally weighted irradiance on a horizontal surface over a specified period of time) and erythemally effective UV dose received by an anatomical site (here called personal dose or exposure on a specific anatomical site) were investigated. Personal doses received by the chest were determined using polysulfone dosimetry. Exposure Ratio (ER), defined as the ratio between the personal dose and the corresponding ambient dose during the same exposure period, was then calculated. Measuring of skin color in the Commission Internationale de l'Eclairage L (luminance), a (redness), b (yellowness) system and skin temperature were also carried out on the inner upper arm (nonexposed skin site) and on the chest. It was found that the median value of ER was 0.20 (min: 0.09 and max: 0.34) for suntanned individuals, it was 0.17 (min: 0.13 and max: 0.42) for non-suntanned individuals and it was 0.19 (min: 0.14 and max: 0.34) for photosensitive individuals. There were no significant differences across the groups in their median ER scores. In addition, the statistical analysis showed that L on the exposed site before exposure demonstrated consistently higher median scores after exposure in all groups. The b value after exposure was significantly lower than before exposure in all participants, while no significant differences for a were observed before or after exposure between or within the groups. Our findings suggest that photodermatoses are not significantly related to ER and to the changes in biological markers due to too short-term UV exposure.     

INDUCTION OF SKIN TUMORS IN THE RAT BY SINGLE EXPOSURE TO ULTRAVIOLET RADIATION

Abstract— The dose response for tumor induction in albino rat skin by single exposures of UV radiation has been characterized. The shaved dorsal skin of 202 animals was exposed to either of two sources: one emitting a broad spectrum of wavelengths from 275 to 375 nm, and the other emitting at 254 nm. Skin tumors began to appear within 10 weeks of exposure and continued to appear for 70 weeks. The highest tumor yield was 5.5 tumors per rat and occurred when the rats were exposed to 13.0 times 10⁴ J/m² of the 275–375 nm UV. The 275–375 nm UV was about eight times as effective as the 254 nm UV for the induction of tumors throughout the exposure range from 0.8 times 10⁴ to 26.0 times 10⁴J/m². Tissue destruction and hair follicle damage was found at the highest exposure to 275–375 nm UV but at none of the exposures to 254 nm UV. Repeated weekly exposures to 275–375 nm UV proved less effective than an equivalent single exposure for inducing tumors, even though the multiple exposures caused more severe skin damage. The transmission of the UV through excised samples of rat epidermis indicated that the exposure to the basal cell layer was about 3% of the surface exposure at 254 nm and about 15% of the surface exposure between 275 and 320 nm. The dependence of tumor yield on UV exposure was linear for 254 nm UV but was more complex for the 275–375 nm UV. For the latter more tumors were produced per unit exposure at lower exposures than at higher exposures.     

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.     

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.     

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.