Quantification of biologically effective environmental UV irradiance

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Adv Space Res Vol 26, No 12, pp 1983-1994.2000 0 2001 COSPAR Pubhshed by Elsevler Science Ltd All nghts reserved Pnnted III Great Bntain 0273- 1177100$20 00 + 0 00 PII SO273-1177(00)00172-1

QUANTIFICATION OF BIOLOGICALLY EFFECTIVE ENVIRONMENTAL UV IRRADIANCE G Hot-neck

German Aerospace Center (DLR), Institute of Aerospace Medlcmne,RadzatlonBiology, D-51170 Koln, Germany

ABSTRACT To determme the impact of envnonrnental W radiation on human health and ecosystems demands momtormg systems that weight the spectral nradrance according to the biological responses under consideration In general, there are three different approaches to quantify a btologrcally effective solar u-radiance (1) weighted spectroradiometry where the brologrcally weighted radiometrrc quantrties are derived from spectral data by multtphcatron wrth an action spectrum of a relevant photobtologrcal reaction, e g erythema, DNA damage, skm cancer, reduced productivity of terrestnal plants and aquatic foodweb, (ii) wavelength mtegratmg chemical-based or physical doslmetrrc systems wrth spectral sensmvmes similar to a brological response curve, and (111)brologrcal dosimeters that directly we&t the madent W components of sunhght 111relation to the effectiveness of the dfierent wavelengths and to mteractrons between them Most brological dosrmeters, such as bactena, bacteriophages, or btomolecules, are based on the W sensmvrty of DNA If precisely charactertzed, brologrcal dosrmeters are apphcable as field and personal dosrmeters 0 2001 COSPAR Published by Elsevler Science Ltd All rights reserved INTRODUCTION Stratosphenc ozone is a protective filter of our atmosphere by absorbmg most of the brologrcally harmful radiation of our sun m the W-C (190-280 nm) and short wavelength-region of the W-B (280-3 15 nm) Although the W-C and W-B regions contribute only 2 % of the entn-e solar nradnmce prior to attenuation by the atmosphere (Frederick et al 1989) they are mamly responsrble for the hrgh lethahty of extraterrestnal sunlight to hvmg orgamsms (Homeck and Bra&, 1992) With decreasing stratosphenc ozone concentration, the spectral drstrrbution of ground based W radratron changes srgmficantly more and more W-B radiation reaches the surface of the Earth A depletion of the stratospheric ozone layer was first observed m sprmgtime over Antarctica - commonly termed as “ozone hole” -, and 1s now rdentrfied globally outside the tropics durmg all seasons of the year (Frederrck, 1993) Hence, the ozone problem winch is predommantly caused by man-made CFCs (chlormated fluorocarbons) (Rowland, 1989) has reached global dimensions Effects are expected (1) for human health, such as increase m skm cancer (Urbath, 1989), suppression of the mnnune system (Hurks et al, 1997) vu-us mductron (Yarosh, 1992) and ocular damage (Zrgman, 1993) (11)for terrestrral plants productrvny (Tevrm and Teramura, 1989) and ecosystem balance (SCOPE, 1992) as well as (111)for aquatic ecosystems, both phyto- and zooplankton (Hader, 1997) To determine the imphcatrons of mcreased levels of solar W-B radiation for crrtrcal processes of our biosphere m quantitative terms, an mstrumentatron for W-measurement 1s required that W

1983

G Homeck

1984

weights the spectral nradrance according to the brologrcal responses under consrderatron In thrs paper, the different methods to measure the brologrcally effective W nradrance wrll be discussed BIOLOGICAL SPECTRAL RESPONSES The brologrcal effecttveness of W radiation changes dramatrcally wrth wavelength With decreasing wavelength, the brologrcal effectiveness increases progressrvely and almost exponentrally Thrs phenomenon 1s described by an action spectrum (Prgure 1) It 1s thrs highly wavelength specrficity of biologrcal action spectra m the W-B range and the wavelength specrfic absorptron characterrstrc of atmospherrc ozone that give nse to the global concern on the impact of a depletion of the stratosphenc ozone layer and thereby an increase m W-B upon the biosphere The shape of the action spectrum of the brologrcal phenomenon under consrderatton determmes whether an incremental change m W-B results m srgmficant changes m the brologlcal effectiveness of solar W radiation Thrs phenomenon stresses the need for a brologrcal weighting of solar W n-radiance for assessing its effects on brologrcal systems Health effects of envnonmental W radratron on humans are manifold wrth the mductron of pre-mahgnant and mahgnant skm lesions as the most harmful effects Since the skm 1sthe drrect target of solar W radratron, the action spectrum for the mammal erythema (Prgure 1) has been recommended as reference action spectrum by The Comrmsslon International de 1Bclalrage (CIE) It has been obtamed by averagmg over the spectral responses of vatlous mdlvlduals of different skm types (McKinley and Dlffey, 1987) IO'

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Wavelength I nm Fig 1

Actron spectrum for the mrnnnal erythema which has been recommended by CIE as reference a&on spectrum for assessmg the health impact of envuonmental UV rtiation (data from McKmley and D&y, 1987) Reference wavelength IS h = 298 nm

Although the mnumal erythema 1s1sused as a reference blomarker, it nught not be the proper mdlcator for the assessment of human health nsks from environmental W radlatlon With regard to human skm cancer, DNA 1s thought to be the prmapal molecular target of envtronmental W radiation (Figure 2) Winduced DNA lessons can lead to oncogemc alterations that play important roles m the mductlon of skm

Blologlcally Effechve UV

1985

cancer There 1s stnkmg evrdence that W-Induced DNA damage 1sthe rmtratmg event m unrnunosuppressron, tumor promotron, vnus mductron and finally m photocarcmogenesrs (Yarosh, 1992) Likewise, DNA damage plays a central role m adverse effects of W-B radratron to terrestrral plants (Coohrll, 1989) and aquatic ecosystems (Hader and Worrest, 1991) Therefore, the action spectrum for DNA damage, e g pyrumdme drmer formatron 111DNA of human skm u-radiated m vrvo wrth W (Freeman et al 1989) or a generahzed action spectrum for DNA damage (Setlow, 1974) might be a more reahstrc brologrcal waghtmg fimctron when assessing the health nsks from an mcreasmg W-B portron m the ground-based W spectrum

promotion

progression

Frg 2 Role of DNA lessonsrn W-mdducedhealth risks (basedon Yarosh, 1992) In Figure 3 different action spectra for W-induced health effects are comprled, mcludmg DNA damage (Setlow, 1974), squamous cell carcinoma m race (deGrug1 et al, 1993), and mahgnant melanoma m fish (Setlow et al, 1993) For comparrson, the CIE action spectrum for mnumal erythema 1s also mcluded Wrth mcreasmg wavelength, all action spectra shown sharply decrease m the W-B regron and then level off m the W-A regron Whereas the slope of the action spectra 1s quite smular m the W-B range, the drfferent spectra vary by orders of magmtude m the W-A regron In thrs W regron, m addrtton to DNA, other endogenous chromophores may be involved leading to mdrrect effects on the DNA (Urbach, 1992) The action spectrum for malignant melanoma shows apprecrably hrgh sensrtrvrty in the W-A regron Thrs 1smterpreted as mdrcatmg that light absorbed m melanm 1seffective m mducmg melanomas (Setlow et aE, 1993) However, rt ISnot clear, whether thrs anrmal model 1salso valid for humans Action spectra, like those shown m Figure 3 have been used as brologrcal weighting fiurctrons to qua&y the brologrcally harmful envrronmental W nradrance Thrs 1sdescrtbed m the followmg chapter

G Homeck

1986 10'

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Fig 3 Action spectra for blologuxl responses to environmental UV rtiatlon A DNA damage (from Setlow, 1974), B skm cancer (from de GIU~J~ et al 1993), C rnmmal eqthema (from McKmley and Dlffey, 1987), D mahgnant melanoma (from Setlow et al 1993) Reference wavelength 1s h = 300 nm

MEASUREMENT We&ted

OF BIOLOGICALLY

EFFECTIVE W IRRADIANCE

hectroradiometry

To quantlfL the blologlcal effectiveness of environmental W radiation, the physical dose parameters have to be converted mto blologlcaily meanmgfU dose parameters Biologically weighted radlometnc qua&ties are derrved from the spectral data by multlplymg them with a blologlcal waghtmg function, 1 e an a&on spectrum of a relevant photoblologlcal reaction, e g DNA damage, erythema formation, skm cancer, reduced productlvlty of terrestnal plants, or W sensltlvlty of aquatic ecosystems The resultmg btologlcal effectiveness spectrum IS shown m Figure 4 The blologcally effective n-radiance Eef (W/mz), IS then determmed as follows (Setlow, 1974)

E, = &% (2) 5 (a)da

(1)

with En(A) = solar spectral u-radiance (Wmm2nm-‘), S&l) = a&on spectrum (relative umts), and h = wavelength (nm) Integration of the blologcally effective n-radiance EM over time (e g , a full day) gves the blologcally effective dose Hef (Jrn-“),R(e g , dady dose) (Horneck, 1995) The advantages of the weighted spectroradlometry method he m rts high accuracy, the capablhty to ident@ mfluences by various parameters, to u&e a large vatlety of blologlcal weighting fimcttons and to use the data for the evaluation of model calculattons &gh demands are made on the mstrument speaficatlons, such as high accuracy - especlally at the edge of the solar spectrum m the W-B range, high stray light suppression, high reproduclbdlty and temperature stab&y Frequent cahbratlon mth standard lamps and field mtercompatlsons vvlth other spectroradlometers are mdlspensable (SCOPE, 1992, McKenzie et al, 1993, Webb et al, 1994)

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Frg 4 Solar spectral rrradranceat the Earth’ssurf&e and a brolo8rcalwerghtlngiimctron (actronspectrum) The solar etfectrvenessspectrum 1sdefinedas the product ofthe rrradrancetrmesthe actron spectrum The area under the curve ISthe brologrcallyeffkctrvenradrance (see Eq 1) Spectroradtometers are bulky mstruments and require a large Investment of resources Therefore, there wrll be only a few sites of measurements at selected statrons For field measurement especially at remote sates or for personal dosrmetry, more snnple devrces are requn-ed Wavelength-Integratmn W Doslmetrv Wavelength Integrating W detectors wrth a spectral sensmvrty smnlar to the standard erythema functron are wrdely used The most common detectors are based on the excrtatton spectrum of magnesrum tungsten phosphor wrth associated optrcal filter combmatrons (Berger, 1976), or on photosensmve films, such as the polysulphone frhn (Davrs et al, 1976) or polycarbonate plastics (Wong et al, 1989), or on solid state photodrodes m combmatron with optrcal filters (Drffey, 1987) Because the spectral sensmvrty of most chemrcal or physical broad band radiometers does not closely match wrth the most relevant action spectra, then readmgs must be corrected consrdermg the solar W spectrum, the spectral response of the W detector and the actton spectrum of concern The brologrcally effective W dose He, (Jm-z)~ IS determmed accordmg to the followmg equation H

= jE” 0) &

%(4dA

I El (A) v, VP

F

(2)

wrth En(A) = solar spectral nradrance (Wm-* run-‘), S,@J = actron spectrum (relative umts) u&J = response fkctron of the sensor (relatrve units), F = equivalent dose of monochromatrc radratron (I,) producing the same response of the detector (Jm’*), and h = wavelength (mn) Broad band radiometers are relatively cheap, wrdely used devtce wrth a contmuous data acqmsmon A comprehenstve data collectron exrsts from long-term measurements at several sites m USA (Berger and Urbach, 1982, Scotto et al,

G Homeck

1988

1988), from alpme sites (Blumthaler and Ambach, 1990), m deserts (Kolhas et al, 1988) and m northern hrgh latitudes (Jokela et al , 1993) Polysulphone films as simple means of contmuously mtegratmg W exposure are rugged, econonucal and can be mrmaturrzed whrch enables them to a wade apphcatron m medrcal context, especrally as persona1 dosrmeter (CIE, 1992, Dtiey, 1987, Krms et al, 1998) Brolosncal W Dosrmetry Brologrcal dosrmeters automatically weight the madent W components of sunhght relative to the brologrcal effectiveness of the different wavelengths and any mteractrons between them Ideally, the spectral response of the brologrcal dosimeter 1s tdentrcal to that of the action spectrum of the photobiologrcal effect under consideratton In this case; the brologrcally effective dose Heff 1s equivalent to the mcrdent dose of monochromatrc radiation at a standard wavelength h, whrch would produce the same response as the actual radratton under consideratron (Tyrrell, 1980) It ISgiven by the followmg relation He8 =F

(3)

wrth Heff = brologrcally effective dose (Jmm2),sand F = equivalent dose of monochromatrc W radratron producmg the same brologrcal response (Jm-‘) Intrmsrc Bromarkers for W Exuosure Intrmsrc bromarkers grve a record of the mdrvrdual radiation exposure (e g , of humans, ammals, plants or ecosystems) m measurable umts For momtormg persona1 exposure to envrronmental W radiation, the followmg intrmsrc blomarkers may be apphcable (1) photoproducts mduced m the skm (e g , cyclobutadrpyrumdmes, (6-4) ppmrdme-pyrnmdone adducts and their Dewar valence isomer) (Freeman, 1989, Chadwrck et al, 1995, Young et al, 1997) and then reparr rates, (n) gene mutatrons m the skm (e g , ~53 mutatrons that occur predommantly assoaated wrth skm cancer) (Daya-GrosJean et al, 1995, Ananthaswamy et al, 1998), (111)second messengers m skin cells (e g , regulation of matrix metalloprotemases) (Brennersen et al, 1996), (iv) antibody titers m the blood, and (v) lens turbrdrty that can be measured by fluorescence The first three methods mentioned are mvasrve, require biopsy and are therefore not apphcable for large scale screemng of W exposure of humans However, they should be used to calibrate extrmsrc brologrcal doslmeters 102 IO'

DNA - --. Uracll -T7 - - - Spore Bofilm

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Relauve actron spectra of drfferentbrologrcaldosnneters(from Hoi-neck,1997)

Blologtcally

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1989

Extrmsrc Biolo~;lcal W Dosnneters Extrmsrc biological dosimeters are especially suited for long-term momtormg of global changes m environmental W radiation and its biological implications They are also useful m momtormg W exposure of mdivlduals durmg out-door activities (e g , sknng, lnkmg, gardening, or leisure) or those at specral risk So far, biological W dosrmeters of different levels-of complexny are available, mcludmg (1) biomolecules (e g , the uracil molecule or DNA) (Grof et al., 1996, Regan et al, 1992, Yoshida and Regan, 1997) (n) vnuses (e g bacteriophage Tl, T2, T4, or T7) (Ronto et al, 1994) and (111)bacteria (e g E cob, spores of BaczZZussubtzlrs, or EugZena graczlzs phytoplankton) (Munakata, 1993, 1995, Horneck et al , 1996, reviewed m Horneck 1997) The most commonly used biological W doslmeters are listed m Table 1 Then- action spectra (Figure 5) agree quite well with that for DNA damage (Setlow, 1974) Since W-Induced cancer is probably nntiated by photochermcal changes of the DNA (Yarosh, 1992) a predommant mechanism of W-B, these simple brological dosnneters are suitable to estimate the potential carcmogemc risk of an Increased solar W radiation The biological W dosimeters are simple, robust and functional mdicators of systems at risk (e g , DNA damage, photosynthetic Impairment, reduced biological activity, or loss m vitality) Most of them are well characterized concernmg then photoblological (e g , action spectra) and radiometnc properties and have been cross-calibrated vvlth other W radiometers (Munakata et al , 1996, Furusawa et al , 1998) Table 1 Characteristics of the Most Commonly Used Biological W Dosimeters Biological detector

Biological endpoint

Dosage unit

Apphcation

Reference

Uracil

Drmer formation

Dose to reduce absorbance by e-l

Long-term momtormg

Grof et al, 1996

DNA

Inactivation, dimer Effective dose, eqmvaformation lent to 254 nm (Jm-‘)

Clear tropical marme water (O-3 m depth)

Regan et al, 1992

Bacteriophage T7

Inactivatron of plaque formers

Average number of hits m the population (Iln(N/Nol)

Long-term/contmuous momtormg, measurements in lakes, rivers, ocean

Ronto et al, 1994

Bacterial cells (E colz sp )

Inactivation, mutagenesis, role of repair processes, interactions

Inactivation rate constant, dose equivalent to that at 254 nm, % survival, % enhancement of survival by removal of W-B

Dnu-nal profiles, daily Karentz and Lutze, 1990 totals, vertical dose distribution m natural water

Bactenal spores (B subabs sp )

Inactivation, mutagenesis, spore photoproduct formation

Inactivation rate constant, mutation doubling constant, dose equivalent to that at 254 nm

Dnu-nal profiles, darly Munakata, 1993, 1995 totals, long term momtormg, personal dosimetry

Biofilm

Loss of biological activity

Dose equivalent to that at 254 nm

Long term momtormg, personal dosimetry, trend estimation

Qumtern et al, 1992, Hoi-neck et al, 1996

.

1990

G Horneck

Scope of Apphcatmn ofBmloglcal Doslmetry Bmloglcal UV dostmeters have the potential to be used as personal and field dosimeters complementary to physical UV measurements Their advantages he in the fact 0) that they &rectly weight the incident radlatmn according to its DNA damaging capacity, (n) that they give an integral record of the bmloglcally effective UV dose over a designated period regardless of variations m the weather conditions, 0ii) that they can be used simultaneously at many different sites, and (iv) that they can be attached to mowng targets (e g , persons) with varying onentatmn to the sun A few examples of apphcatmns ofblologacal dosimeters are given m the following Biological film dosimeters, such as the spore dosimeter (Munakata et al, 1998) and the bmfilm (Rettberg and Horneck, 1998) have been integrated m badges to measure the in&wdual UV exposure with regard to its bmloglcal effectweness Bmloglcal dosimeters have also been used to determme the datly and annual profiles ofbmloglcally effectwe environmental UV radmtion m Hungary (Ront6 et al 1994, 1995), m Brazd and Japan (TyrreU, 1978, Munakata, 1993), and m Antarctica (Qumtem et al 1994) Using the spore dostmeter, Munakata (1993) showed m a 14 years study a trend of increase of the bmloglcally effecuve dose of solar UV radmtmn m Tokyo from 1980 to 1993 Using the bmfilm dosimeter m a more than 1 year lasting UV-momtonng campaign m AntarcUca, Qumtern et al (1994) provided experimental proof of an enhanced level of bmlogacally effectwe UV radmtmn during periods of stratospheric ozone depletmn In a space experiment, the bmfilm dosimeter was used to deterrmne the biologically effectwe UV lrra&ance of extraterrestrial sunhght filtered through a set of different cut-off filters to simulate the terrestrial UV radmtmn chmate at different ozone concentratmns Homeck et al (1996) showed that the stratospheric ozone layer reduces the bmlogical effectiveness of extraterrestrial solar radiatmn by three orders of magmtude CONCLUSIONS In order to assess the risks to human health and the bmsphere from an increased UV radmuon as a consequence of increasing stratospheric ozone depletmn, bmlogJcal dostmetry bears the potenUal of providing ad&tmnal mformatmn to physical measurements and model calculaUons Tl~s is based on the fact, that the bmloglcal dosimeters directly weight the incident UV components of sunhght m relatmn to the bmloglcal effectiveness of the different wavelengths and potential interactmns between them However, m order to provide rehable data, a set of criteria has to be met, wtuch are of photobmloglcal and ra&ometnc nature Such a catalogue of criteria for rehable bmloglcal UV dosmaeters has been elaborated within the BIODOS project of the European Commlssmn It includes the following 7 reqmrements A biological dosimeter must/should 1 m&cate a biological effect of possible risk or benefit by solar ra&ation • The reaction must be UV specific (m UV-B and UV-A range) • The reaction should be general • The reaction must indicate a biologically slgmficant process, e g in human health, ecosystem balance, agricultural and fishery productlwty 2 have a spectral response (UV-B and UV-A) m agreement with a specific photoblologlcal process • with respect to monochromatic radmtmn • w~threspect to polychromatlc ra&atlon These acUon spectra (mono- and polychromaUc) must be described with the tughest accuracy possible 3 quantify the bmloglcal effectiveness of solar UV ra&ation in measurable umts that can be • compared with other measurements (e g calculated data from spectroradmmetry, other ra&ometers) • converted into other umts ofphotobmloglcal/me&cal importance (e g MED) The error budget shall be estimated 4 produce reproducible data • the procedure must be standardised

BIologlcally Effectwe UV

1991

the biological sensrtive system must be well defined, e g genetically well defined strams the operation of the dosimeter must be independent of environmental condmons (e g temperature, relative hunudity, ram etc ) l stab&y with time The dosimeter should be positioned m a defined manner, dependmg on the purpose (e g horizontally, personal dosimetry) 5 comply with the general requirements for radiometers l absolute responsivzty to W-B, W-A and W-B plus W-A (cahbratron) 0 relative spectral response 0 hnearity of response (law of reciprocity) 0 angular response The feaszbihty of the biological dosimeter should be proven by mtercompanson with biologically weighted spectroradiometry 6 be robust l have a long shelf hfe l be resistant agamst environmental extremes durmg pre- and post-exposure storage (e g heat, cold, humidny etc ) 7 be suttable for routme measurements l easy handling 0 safe to the environment 0 automatic registration 0 cost-effectiveness l

l

If sufficiently characterized and cahbrated according to the 7 cntena mentioned above, biologzcal doameters are applicable m field measurements and as personal dosimeters ACKNOWLEDGMENT The study was supported by a grant of the European Commission (ENV4-CT950044) REFERENCES Ananthaswamy, H N , A Four-tamer, R L Evans, S Tison, C Medarsko, S E Ullnch, and M L Kripke, ~53 Mutations in Han-less SKH-hrl Mouse Skm Tumors Induced by a Solar Simulator, Photochem Photobzol , 67, 227-232 (1998) Berger D S and F Urbach, A Chmatology of Sunburnmg Ultraviolet Radiation, Photochem Photobzol , 35, 187-196 (1982) Berger, D S , The Sunburmng Ultraviolet Meter Design and Performance, Photochem Photobzol, 24, 587-593 (1976) Blumthaler M and W Ambach, Indicatton of Increasing Solar Ultraviolet-B Radiation Flux m the Alpme Regions, Sczezzce,248,206-207 (1990) Brenneisen, P , J Oh, M Wlaschek, J Wenk, K Briviba, C Hommel, G Hermann, H Sies, and K Scharffetter-Kochanek, Ultraviolet B Wavelength Dependence for the Regulation of Two MaJor Matrot-Metalloprotemases and then Inhibitor TIMP-1 m Human Dermal Fibroblasts, Photochem Photobzol , 64, 649-657 (1996) Chadwick, C A, C S Potten, 0 Nikaido, T Matsunaga, C Proby, and A R Young, The Detection of Cyclobutane Thymme Drmers, (6-4) Photolesions and the Dewar Photoisomers m Sections of WIrradiated Human Skm Using Specific Antibodies, and the Demonstration of the Depth Penetration Effect, J Photochem Photobzol B Bzol ,28, 163- 179 (1995)

1992

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CIE Techmcal Report, Personal Doslmetry of W Radiation, Pub No CIE 981992

Coohrll, T P , Ultravrolet Action Spectra (280 to 380 nm) and Solar Effectiveness Spectra for Hrgher Plants, Photochem Photobzol ,50,45 l-457 (1989) Davis, A, G H W Deane, and B L Drffey, Possible Dosrmeter for Ultravrolet Radiation, Nature, 261, 169-170 (1976) Daya-GrosJean, L , N Dumaz, and A Sarasm, The Specificity of p53 Mutation Spectra m Sunhght Induced Human Cancers, J Photochem Photobzol B. Bzol., 28, 115-124 (1995) deGruil1,F R , H J C M Sterenborg, P D Forbes, R E Davies, C Cole, G Keltken, H van Weelden, H Slaper and J C van der Leun, Wavelength dependence of skm cancer mduction by ultravrolet radratron of albino hairless rmce, Cancer Res 53 (1993) 53-60 Drffey, B L , A Comparrson of Dosimeters Used for Solar Ultravrolet Radiometry, Photochem Photobzol, 46, 55-60 (1987) Frederick, J F , Ultravrolet Sunhght Reachmg the Earth’s Surface a Review of Recent Research, Photothem Photoblol, 57 175-178 (1993) Frederick, J E , H E Snell, and E K Haywood, Solar Ultravrolet Radratron at the Earth’s Surface, Photochem Photoblol, 51,443-450 (1989) Freeman, S E , H Hacham, R W Gange, D J Maytum, J C Sutherland, and B M Sutherland, Wavelength Dependence of Pynmrdme Drmer Formatron m DNA of Human Skm Irradiated zn sztu wrth Ultraviolet Light, Proc Nat1 Acad Scz USA, 86, 5605-5609 (1989) Furusawa, Y ,L E Qumtern, H Holtschmrdt, P Koepke, and M Sarto, Determmatron of Erythemaeffective Solar Radiation m Japan and Germany wrth a Spore Monolayer Film for the Detection of UVB and UVA - Results of a Field Campargn, AppZ Microbzol Blotechnol , 50, 597-603 (1998) Grof, P , S Gaspar, and Gy Ronto, Use of Uraal Thm Layer for Measurmg Brologically Effective W Dose, Photochem Photoblol 64, 800-806 (1996) Hader, D -P (ed ), The Effects of Ozone Depletzon on Aquatzc Ecosystems, R G Landes Company, Austm, TX USA (1997) Hader, D -P and R C Worrest, Effects of Enhanced Solar Ultravrolet Radiation on Aquatic Ecosystems, Photochem Photoblol ,53, 7 17-725 (1991) Horneck, G , Quantification of the Brologrcal Effectiveness of Environmental W Radratron, J Photochem Photoblo B Blol ,31,43-49 (1995) Horneck, G , Biological W Dosimetry, m The Effects of Ozone Depletion on AquatIc Ecosystems, edited by D P Hader, pp 119-142, R G Landes Company, Austm, TX, USA (1997) Horneck, G and A Brack, Study of the Ongm, Evolution and Distrrbutron of Lrfe wrth Emphasis on Exobrology Experrments m Earth Orbtt, m Advances m Space Bzology and Medxmne, Vol 2, edrted by S L Bontmg, pp 229-262, JAI Press, Greenwrch, CT (1992) Horneck, G, P Rettberg, E Rabbow, W Strauch, G Seckmeyer, R Facms, G Rertz, K Strauch, and J U Schott, Brologrcal Dosmetry of Solar Radiation for Different Simulated Ozone Column Thrckness J Photochem Photoblol B B1o1, 32, 189-196 (1996) Hurks, H M H , C Out-Lumng, B J Vermeer, F H J Claas, and, A M Mommaas, In Sztu Action Spectra Suggest that DNA Damage 1s Involved m Ultraviolet Radratron-Induced Immunosuppressron m Humans, Photochem Photobrol ,66, 76-8 1 (1997) Jokela, K , K Leszczynslu and R Vrsuri, Effects of Arctic Ozone Depletion and Snow on W Exposure in Fmland, Photochem Photobzol , 58, 559-566 (1993) Karentz, D and L H Lutze, Evaluation of Biologically Harmful Ultraviolet Radratron m Antarctica wrth a Brological Doslmeter Designed for Aquatic Envtronments, Lzmnol Oceanogr , 35, 549-561 (1990) Kolhas, N , A H Bager, and I Sadiq, Measurements of the Solar Middle Ultravrolet Radiation m a Desert Envnonment, Photochem Photoblol , 47, 565-569 (1988)

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