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ABSTRACT:
The Stratospheric Ozone and Human Health World Wide Web (WWW) site supports access to interdisciplinary data and information resources that integrate remote sensing and public health data. Through its Socioeconomic Data and Applications Center (SEDAC), CIESIN has developed near-real time estimates of ultraviolet (UV) radiation dose at the Earth's surface derived from ozone data from NASA satellites and an atmospheric transmission model. Global maps are updated daily as new data become available. The UltraViolet Interactive Service (UVIS) provides hourly, daily, and monthly estimates of health-related biologically effective doses from 1979-1990 for selected locations across the United States. UVIS is accessible through an interactive query engine that allows users to visualize data of interest. Other on-line services include a searchable bibliography of UV-related publications, impact assessment reports from the United Nations Environment Programme (UNEP), and access to relevant epidemiological data from around the world. The Stratospheric Ozone and Human Health WWW site may be accessed at http://sedac.ciesin.org/ozone

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1.   Introduction

The Socioeconomic Data and Applications Center (SEDAC), operated within the Consortium for International Earth Science Information Network (CIESIN), is one of eight Distributed Active Archive Centers (DAACs) within NASA's Earth Observing System Data and Information System (EOSDIS). SEDAC's role in EOSDIS is to synthesize earth science and socioeconomic data into integrated products, and to provide a gateway to socioeconomic data and information around the world. Towards this objective, SEDAC has developed the Stratospheric Ozone and Human Health project website, the purpose of which is to provide unique and hard-to-find data and resources in the areas of ultraviolet (UV) radiation, ozone, and human health impacts of UV exposure for use by researchers, educators, government officials, health providers, students, and the general public. These resources include: the development of near-real time maps of estimated global UV radiation dose generated using atmospheric ozone measurements from NASA; the UltraViolet Interactive Service (UVIS), which provides interactive access to hourly, daily, and monthly-averaged modeled UV dose levels at several locations across the United States spanning the years 1979-1990; and a searchable bibliographic database containing more than 3,300 citations in the areas of ozone depletion, UV radiation, human and ecosystem health, and related topics. Full-text documents on the effects of ozone depletion and ozone science research from the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) are available on the website, and access is provided to health-related data and resources available at remote locations. A brief discussion of these data resources is presented here.

2.   Geophysical and Exposure-Related Inputs for the Near-Real Time Global UV Dose Maps and the UltraViolet Interactive Service (UVIS)

The UV dose quantities calculated for the global UV dose maps and the UVIS were generated using an atmospheric radiative transfer model (RTM) The RTM used in this study has been described previously by Charache et al. (1994), which simulates the effects of absorption by ozone and multiple scattering by aerosol, molecules, and multiple cloud layers. Several input data sets are incorporated into the model to generate these dose quantities: ozone and cloud data from the National Aeronautics and Space Administration (NASA), surface meteorological data from the National Climatic Data Center (NCDC), elevation data from the National Center for Atmospheric Research (NCAR), and UV exposure thresholds for particular biological endpoints from several research groups around the world.

A) Total Column Ozone Data: TOMS

Near-real time estimates of total column ozone levels from the Total Ozone Mapping Spectrometer (TOMS) instrument on board the Earth Probe (EP) satellite are made available from NASA via file transfer protocol (ftp) from the Goddard Space Flight Center (GSFC). Historical estimates of total column ozone were taken from the TOMS instrument on board the Nimbus-7 satellite. These historical data are distributed by NASA from the Goddard Space Flight Center in CD-ROM format or via an anonymous ftp server. TOMS provides daily total column ozone measurements on a near-global scale at a 1x1.25 degree latitude/longitude resolution.

B) Cloud Data Inputs: ISCCP and SAMSON

Cloud optical depth values are taken from the International Satellite Cloud Climatology Project (ISCCP) C-2 data collection. These data are compiled from a suite of polar-orbiting and geostationary platforms and aggregated into 2.5x2.5 degree latitude/longitude gridded data product. Data are given as monthly averages for the entire globe from 1983-1990, with recent updates extending to later years. The ISCCP data collection is available on CD-ROM from the NASA Langley Research Center.

Hourly cloud parameters (total sky cover, opaque sky cover, ceiling height) were taken from the Solar and Meteorological Surface Observation Network (SAMSON) CD-ROM compilation, distributed by the National Climatic Data Center (NCDC). The database contains hourly observations at most stations from 1961-1990. These data are used to infer the type of cloud present and the amount of sky coverage in order to assign cloud optical depth and the clear/cloud fractional value used to weight irradiance values in partly cloudy conditions.

C) Elevation Inputs to the Model

The effect of elevation on surface UV dose levels is incorporated into the model using an empirical relation for the increase in surface irradiance as a function of altitude above sea level, given by Madronich (1993) as a 6% increase per kilometer above sea level. Elevation data are taken from the Rand 1x1 degree gridded elevation/bathymetric dataset, distributed by the National Center for Atmospheric Research (NCAR).

D) Calculation of Biologically Effective Dose

The UV irradiance at a given wavelength [I()] calculated at the surface must be weighted with an action spectrum to obtain the potential biologically effective dose (BED). The BED is typically defined as the maximum potential dose amount available to cause a particular biological effect, e.g. the amount of dose available to cause sunburn on unprotected skin. An action spectrum can be defined as a parameter that describe the relative effectiveness of energy at a different wavelengths of light in producing a particular biological response. Biological response may refer to effects at a molecular level, such as DNA damage, or at a whole organism level, such as plant growth. Several action spectra are shown in Figure 1: the erythemal action spectrum given by McKinlay and Diffey (1987); the nonmelanoma SCUP-m spectrum of de Gruijl and van der Leun (1994); the spectrum for melanoma induction in swordtail-platyfish hybrids (Setlow et al., 1993); and the DNA damage action spectrum (Setlow, 1974).

Figure 1. Examples of action spectra.

The potential BED at the surface for a given instant in time is found by the product of the UV spectrum I() and the action spectrum A(), summed over the appropriate wavelength range. For the daily dose, UV irradiance is calculated at 1/2 hour time steps over the course of the day and summed to obtain the total daily dose.

3.   Near-Real Time Estimates of Global UV Dose

Daily erythemal (sunburning) dose and the well-known Ultraviolet Index (UVI) data are calculated for the entire surface of the Earth at a 1x1 degree latitude/longitude resolution using an atmospheric radiative transfer model (RTM) and data inputs described in section 1. The global maps representing these data are generated by a multi-step process that begins by downloading the latest day's EP/TOMS ozone data made available on the NASA/GSFC ftp server. The RTM code then uses these ozone values to estimate the clear sky dose values at the surface of the Earth. These data are then formatted for input into the Arc/Info® Geographical Information Systems (GIS) software package to create the latitude/longitude projection image. The postscript file generated in Arc/Info® is then converted to a Graphics Interchange Format (gif) image, and placed in the appropriate data directory for display on the web page. These maps represent clear sky estimates of the UV dose variables, and are updated daily as new data become available from NASA. Previous day's maps are archived on the website, thus allowing users to visualize changes in UV dose levels over time. Figure 3 shows an example of the daily erythemal dose estimates for January 1, 1998. Note that the highest levels appear in higher elevations of South America, while low values are found over nearly all of the Northern Hemisphere due to the low sun intensity in the winter season.

Figure 2.   Clear sky daily erythemal dose levels for January 1, 1998.

4.   The UltraViolet Interactive Service (UVIS)

The UVIS is an interactive, custom-query service that allows for on-screen visualization of hourly, daily, and monthly-averaged biologically effective dose amounts for nine locations across the United States encompassing a twelve-year time frame between 1979-1990. All data were calculated using the RTM and data inputs described in section 1. The nine locations for which the data were developed are Albuquerque NM; Atlanta GA; Detroit MI; Honolulu HI; Minneapolis-St. Paul MN; New Orleans LA; Salt Lake City UT; San Francisco-Oakland CA; and Seattle WA. These sites were selected based on their involvement with the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. This program, initiated in the early 1970s, requires the monitoring of cancer incidence in these areas, including melanoma of the skin, which is known to have UV exposure as a risk factor. With a long-term epidemiological record of melanoma in these areas, it was determined that these sites would be a sensible starting point for the UVIS project. The number of sites could be expanded to other locations that have epidemiological records, or that meet other criteria deemed relevant by the epidemiological and/or public health communities.

There are five different UV dose variables that can be visualized through the UVIS: erythemal dose, non-melanoma skin cancer dose, DNA-damage dose, "fish-melanoma" dose, and unweighted UV dose. The first four variables are found by weighting the UV spectrum (290-400 nm) with its corresponding action spectrum (described in section 1D), whereas the unweighted UV dose applies no action spectrum and simply reflects the total integrated UV dose amount in the 290-400 nm range.

The UVIS allows for simultaneous viewing of UV data from multiple cities, as well as viewing of multiple dose variables for a single city. A new feature recently added to the service allows for plotting of daily or monthly-average UV dose simultaneously with TOMS ozone data, thereby allowing the user to analyze the relationship between UV dose and ozone levels. An example of these data are given in figure 4, in which erythemal dose and ozone are plotted for Detroit during June 1989.

Figure 3. Simultaneous UV-ozone data plot obtained from the UVIS.

5.   Searchable Bibliographic Database

The searchable bibliographic database contains more than 3,300 scientific and general citations from journal articles, conference proceedings and presentations, books, and other periodicals in the areas of ozone depletion, ultraviolet radiation, ecological and human health, technology, immunology, CFCs, and other related topics. These citations are stored in a relational database that allows users to query the database using one or more search options:

• free text
• author
• subject category
• publication source
• year(s) of interest
• title

Each citation contains one or more subject categories which identifies it with a particular discipline. This field allows users to query the database on one of eight broadly defined categories: Atmospheric Physics and Chemistry, Terrestrial Ecosystem Effects, Aquatic Ecosystem Effects, Human Health Effects, Materials Effects, Biogeochemical Cycles Effects, Photobiology and Cellular Research, and General Information and Articles. This added field allows users to retrieve a categorized list of citations that can narrow or expand a generalized search depending on the other search criteria implemented with a given query. This searchable bibliographic service can help researchers identify relevant publications in their area of interest quickly and easily, thereby saving valuable time and resources.

6.   On-Line Publications

Several on-line publications spanning a wide range of disciplines are also available at the Stratospheric Ozone and Human Health website. The United Nations Environment Programme (UNEP) has provided interim reports on the status of environmental effects of ozone depletion, as well as the full text to the Environmental Effects of Ozone Depletion: 1994 Assessment. This document is regarded as the preeminent source of information regarding the impacts of ozone depletion on the environment. Also provided is the World Meteorological Organizations (WMO) Report of the Third Meeting of the Ozone Research Managers (1996), which provides a report of ozone monitoring and research activities by participating countries. A large collection of peer-reviewed publications in leading scientific journals is also available in CIESIN's Thematic Guide on Ozone Depletion. This resource contains overview summaries and access to peer-reviewed papers in the areas of ozone depletion, potential impacts on human and ecosystem health, chlorofluorocarbons (CFCs), and environmental policy.

7.   Human Health Data Resources

The potential impacts of ozone depletion on human health as a result of increased ultraviolet radiation are well documented in many scientific journals and international assessment panel reports, such as the UNEP reports mentioned in section 5. However, data relevant to the UV radiation and human health issue are widely scattered and often difficult to locate. Sources of such data include local and regional disease registries, national and international surveys, and epidemiological studies. The goal of this component of the Stratospheric Ozone and Human Health website is to provide a centralized directory from which users may access available source of data related to human health effects of ultraviolet radiation exposure. An example of some of the data sources accessible through this directory include U.S. state cancer registries, provincial cancer registries from Canada, the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) data, the World Health Organization's (WHO) mortality database, and the North American Association of Central Cancer Registries (NAACCR).

8.   Conclusion

The Stratospheric Ozone and Human Health project web site provides access to unique and hard-to-find information resources in the areas of UV radiation, ozone depletion, and human health that integrate a variety of geophysical and health-related data. Access to relevant data has become a high priority in the interdisciplinary scientific community, and by making these resources available via the WWW, researchers can save a significant amount of time and energy finding the information needed to facilitate their investigations.

Acknowledgments. This work was supported through CIESIN under NASA Contract NAS5-32632 for the development and operation of the Socioeconomic Data and Applications Center (SEDAC). The opinions, conclusions, and recommendations contained herein represent those of the author and are not necessarily those of CIESIN or SEDAC, nor has the accuracy of the data contained herein been verified or guaranteed by CIESIN or SEDAC.

References

Charache, D. H., V. J. Abreu, W. R. Kuhn, and W. R. Skinner, Incorporation of multiple cloud layers for ultraviolet radiation modeling studies. Journal of Geophysical Research, Vol. 99, pp. 23,031-23,040, 1994.

de Gruijl, F. R., and J. C. Van der Leun, Estimate of the wavelength dependency of ultraviolet carcinogenesis in humans and its relevance to the risk assessment of a stratospheric ozone depletion, Health Physics, Vol. 67, pp. 319-325, 1994.

Madronich, S, UV Radiation in the natural and perturbed atmosphere, Chapter 2 in UV-B Radiation and Ozone Depletion: Effects on Humans, Animals, Plants, Microorganisms, and Materials. M Tevini, ed., Lewis Publishers, Boca Raton, Florida, pp. 17-69, 1993.

McKinlay, A. F., and B. L. Diffey, A Reference action spectrum for ultra-violet induced erythema in human skin, in Human Exposure to Ultraviolet Radiation, Risks and Regulations, W. F. Passchier and B. F. M. Bosnjakovic, ed., International Congress Series 744, pp. 83-87, 1987.

Setlow, R. B., The wavelengths in sunlight effective in producing cancer: a theoretical analysis, Proceedings of the National Academy of Sciences USA, Vol. 71, pp. 3363-3366, 1974.

Setlow, R. B., E. Grist, K. Thompson, and A. D. Woodhead, Wavelengths effective in induction of malignant melanoma. Proceedings of the National Academy of Sciences USA, Vol. 90, pp. 6666-6670, 1993.