Following the rapid developments in the UV-B measurement techniques and the rapidly growing research in the field in the late 80's and early 90's, we organized a large gathering of distinguished experts in a NATO Advanced Study Institute, held in Halkidiki, Greece on October, 2-11. 1995. The Institute was organized so as to include state of the art lectures on most aspects of solar ultraviolet radiation and its effects. This was achieved by extended lectures and discussions given in five sessions by 27 lecturers and a demonstration of filed measurements and calibration techniques at the end of the Institute. The ASI began with the sun and fundamentals on solar radiative emissions and their variability in time and continued with the interaction of solar Ultraviolet with the atmosphere through the complex scattering processes and photochemical reactions involved. Particular emphasis was given to changes in atmospheric composition imposed by different manifestations of the solar activity cycle. as well as on the modelling of radiative transfer through the atmosphere and the ocean under variable environmental conditions. Overviews on the ozone issue. its monitoring and variability were extensively discussed with emphasis on the observed acceleration of ozone decline in the early 90's. This acceleration had as a consequence, significant increases in UV-B radiation observed at a few world-wide distributed stations.

The inspiration for this monograph derived from the realization that human technical capacity has become so great that we can, even without malice, substantially modify and damage the gigantic and remote outer limit of our planet, the stratosphere. Above the atmosphere of our ordinary experience, the stratosphere is a tenuous layer of gas, blocked from rapid exchange with the troposphere, some twenty kilometers above the surface of the earth, seldom reached by humans, and yet a fragile shell which shields life on earth from a band of solar radiation of demonstrable injurious potential. It is immediately obvious that if stratospheric ozone were reduced and consequently the intensity of solar ultraviolet radiation reaching the earth's surface were increased, then human skin cancer, known to be related to solar ultraviolet exposure, would also be increased. But how does one even begin to estimate the impact of changed solar ultraviolet radiation on such a diverse. interacting, and complex ecosystem as the oceans? Studies which I conducted in Iceland focused on this question and were noted to the Marine Sciences Panel of the Scientific Affairs Committee of NATO by Professor Unnsteinn Stefansson, leading to a request to investigate the possibility of organizing a NATO sponsored Advanced Research Institute on this topic.

Inadvertent alterations of the earth's atmosphere by man's activities are now of regional and even global proportion. Increasing concern has been focused in the last decade on consequences of acid rain, carbon dioxide enrichment of the atmosphere and reduction of ozone in the upper atmosphere. The latter two problems are of truly global scale. This book focuses on the atmospheric ozone reduction problem and the potential consequences for plant life. unlike carbon dioxide enrichment, reduction of the total atmospheric ozone column has not yet taken place to a noticeable degree -- it is a problem of the future. The processes leading to ozone reduction involve time periods on the scale of decades. However, by the same token, if society finds ozone reduction to be unacceptable it will take even longer for the process to be reversed. Thus, anticipation of the consequences of ozone reduction is of obvious importance. Speculation of the possibility of ozone reduction first appeared in the early 1970's and was focused on the consequences of the injection of large quantities of nitrogen oxides into the upper atmosphere by supersonic aircraft flying at high altitudes. Other sources of nitrogen oxides originating from the earth's surface were also considered. With further refinement, the concerns of nitrogen oxide pollution of the upper atmosphere were diminished since the quantities likely to be involved were insufficient to cause a serious threat to the ozone layer.

Gafchromic external beam therapy (EBT) films have been widely used in clinical dosimetric applications due to their high sensitivity to ionizing radiation such as X-ray and electron beams. In 2011, International Specialty Products (ISP) introduced a new generation of films called EBT3 film. The films exhibit color changes from light green to darker color with the increment of absorbed doses of ionizing radiation. The color changes of the films are commonly characterized using flatbed reflective scanner, and subsequently being used to predict the absorbed dose. Besides ionizing radiation, EBT3 films have also been proven to have high sensitivity towards ultraviolet radiation, and hence, make it a promising method in measuring solar ultraviolet radiation exposure. This research book presents a comprehensive visible spectroscopy method in characterizing the color changes of EBT3 films specifically for the measurement of solar ultraviolet exposure. The visible spectroscopy method and analysis presented in this book is also applicable for other types of transparent films for radiation dosimetry.

This textbook provides a comprehensive understanding of the scattered and filtered solar UV environment, the techniques to measure this radiation and the resulting UV exposures to humans. As is well known, the incidence of skin cancer and sun-related eye disorders can be reduced by minimization exposure to UV radiation. The book aims to quantify, understand and provide information on the effects of filtered and scattered UV light.

In the history of science the opening up of a new observational or experimental window is always followed by an increase in knowledge of the subject concerned. This is also the case with the subject of this book, ultraviolet radiation (hereafter UV). In principle, the ultraviolet range might be just one more of these windows, of no particular importance. However, the energy per UV photon provides the main peculiarity, its magnitude being great enough to produce important ch- ical reactions in the atmospheres of planets and satellites, thereby a?ecting the transmission of this radiation to the ground. The Sun is the main natural source of UV radiation in the Solar System and our planet is the body where its in?uences can be best tested and the only one where its relation with life can be studied. However, the terrestrial atmosphere blocksmostofthephotonsinthiselectromagneticrangeandastronomershavehad to develop various techniques (balloons, planes and rockets) to cross this barrier and access the information. These tools have been used in parallel to investigate the physical properties of the terrestrial atmosphere and the interaction of its constituents with light. This book will addresses most of these topics.

Sunlight is part of everyday life and we accept it as good-and good it is in a number of ways. The sun is our source of warmth, and of the light by which we see. It is, in fact, the source of the energy with which life continues on earth. It furnishes energy for photosynthesis, and the pro ducts of photosynthesis constitute our food, building materials, and fuel. A steady state of balance and fine interrelationships exists between life on earth and all the forces and stresses in nature. This book will pin point the balance and relationships we share with sunlight. Our primary focus will be on the ultraviolet radiation of the sun, and on the ultraviolet photobiology of life on earth. This is the story of the effects of the sun's ultraviolet radiation, both good and bad, on all of us and all of life. We will explore the nature of the sun's ultraviolet radiation as it reaches the earth's surface today, and as it probably affected the earth in the distant past; and examine the effect of such radiation on all life, unicellular organisms as well as multicellular plants and animals. The effects of the sun's ultraviolet rays are primarily a result of their action upon cells, and secondarily, a result of their interactions between cells. The cell of a multicellular organism-man included-is also part of the tissue of an organ, and the organ is part of the whole organism.