The Connection Between Ozone Depletion and UVB Radiation
Reductions in ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Another study confirmed the relationship between reduced ozone and increased UVB levels in Canada during the past several years.
Effects on Human Health
Laboratory and epidemiological studies demonstrate that UVB causes nonmelanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to cataracts. All sunlight contains some UVB, even with normal ozone levels. It is always important to limit exposure to the sun. However, ozone depletion will increase the amount of UVB and the risk of health effects.
Effects on Plants
Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Despite mechanisms to reduce or repair these effects and a limited ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation.
Indirect changes caused by UVB (such as changes in plant form, how nutrients are distributed within the plant, timing of developmental phases and secondary metabolism) may be equally, or sometimes more, important than damaging effects of UVB. These changes can have important implications for plant competitive balance, herbivory, plant diseases, and biogeochemical cycles.
Effects on Marine Ecosystems
Phytoplankton form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. The position of the organisms in the euphotic zone is influenced by the action of wind and waves. In addition, many phytoplankton are capable of active movements that enhance their productivity and, therefore, their survival. Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB. One study has indicated a 6-12% reduction in the marginal ice zone.
Solar UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians and other animals. The most severe effects are decreased reproductive capacity and impaired larval development. Even at current levels, solar UVB radiation is a limiting factor, and small increases in UVB exposure could result in significant reduction in the size of the population of animals that eat these smaller creatures.
Effects on Biogeochemical Cycles
Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important trace gases e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere-atmosphere feedbacks that attenuate or reinforce the atmospheric buildup of these gases.
Effects on Materials
Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation. Today's materials are somewhat protected from UVB by special additives. Therefore, any increase in solar UVB levels will therefore accelerate their breakdown, limiting the length of time for which they are useful outdoors.
For more information on how ozone depletion affects either human health or the environment, follow the links below.
This is the most recent World Meteorological Organzation and United Nations Environmental Programme assessment. It contains the most up-to-date understanding of ozone depletion and reflects the thinking of over 250 international scientific experts who contributed to its preparation and review. Alternate Link:
This component of the "Scientific Assesment of Ozone Depletion: 2002" presents 20 questions and answers about the often-complex science of ozone depletion. The answers were all prepared by and reviewed by a large international group of scientists. It is written for a broad readership of decision-makers, educators, students, and the general public.
This introduction to ozone depletion first describes the causes and effects of ozone depletion, and then explains some of the solutions. Follow Farley the reporter as he learns about this issue. Links are provided along the way to more detailed information found elsewhere on the site. Three versions are available: a web-viewable set of illustrated panels, a text version, and an Adobe Acrobat version.
EPA operates and maintains a network of Brewer spectrophotometers throughout the United States, measuring full-sky spectrally-resolved solar radiation in the UV-B and UV-A bands. Visitors can create graphs of daily UV and ozone levels and download the data.
This site is full of useful data and information. Download original ozone level data and see movies and graphics of ozone depletion and the Antarctic ozone hole. The site also lets you find the ozone level over your house!
Features a 90-day archive of the latest images from global, northern hemisphere, and southern hemisphere ozone measurements. Also features animations and ozonesonde measurements from Antarctica. Some of these images are also available from the NOAA Climate Prediction Center.
This site provides the full text of an enormous number of papers on ozone depletion.
Ozone Science Frequently Asked Questions (FAQ), Answers, and References (not maintained by EPA; thanks to Robert Parson)
This set of questions and answers provides carefully cited information. It goes into considerable detail and provides numerous references to original research. The FAQ is available at
several sites in plain text.