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American Academy of Dermatology (AAD) web site at: http://www.aad.org/public/DermatologyA-Z/Index.htm. 2006.

Aura mission. Web pages at: http://aura.gsfc.nasa.gov/. and http://www.nasa.gov/mission_pages/aura/main/index.html.

Australian Government Bureau of Meteorology (Austr. Gov) web site at: http://www.bom.gov.au/announcements/uv/. 2006.

Brannon H. About Health and Fitness web site. UVA radiation. Web essay at: http://dermatology.about.com/cs/agingskin/g/uva.htm. 2006.

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Notes

[1] Ultraviolet light was discovered by Johann Wilhelm Ritter (1776-1810) in 1801 after hearing of William Herschel’s discovery of infrared light beyond the red end of the visible spectrum.  Ritter noted blue light caused silver chloride to turn black more efficiently than red light.  He also discovered that “light” beyond the violet portion of the visible spectrum displayed an intense reaction in this regard.  From: http://coolcosmos.ipac.caltech.edu//cosmic_classroom/classroom_activities/ritter_bio.html.

[2] UVA, UVB, and UVC are sometimes used in a hyphenated form, such as UV-B.

[3] “Germicidal” or “bactericidal” agents are chemicals, medications, or forms of radiation that kill bacteria.  These agents often kill viruses as well.  Bacteriostatic agents are those which stop the growth of bacteria but do not necessarily kill them. 

[4] “Acute” is a medical term for a rapid (minutes to hours) effect while “chronic” is a medical term for a long duration (weeks to months) effect. 

[5] Inflammation is a term used since ancient times to describe a combination of redness, swelling, pain, and heat in an area subject to physical, chemical, or infectious injury.  It is part of the body’s response to injury, and it is the first part of the healing mechanism.  It is mediated through a complex system of chemicals released from injured cells, chemicals and cells brought to the injured area via the blood stream, and cells that make their own way to the injured area through cellular locomotion. 

[6] Vitamin D consists of a complex group of hormones that help regulate body levels of calcium and phosphorus which in turn controls the mineralization of bone.  Individuals with adequate exposures to sunlight do not require dietary vitamin D.  Lack of vitamin D leads to various childhood and adult diseases, such as rickets.

[7] In 1839 Christian Schonbein (1799-1868) smelled a previously unknown component of air during electrolysis of water, ascribing this smell to a new compound he called “ozone” which means ill-smelling in Greek.  Jacques-Louis Soret (1827-1890) in 1864 recognized the structure of ozone (the dioxide of the O atom).  From Crutzen (2000).

[8] The troposphere is the lowest level of the Earth’s atmosphere.  It extends up to a height of approximately 10 to 15 km, and its temperature decreases steadily with altitude.  The troposphere and the stratosphere were named by Leon-Philippe Teisserenc de Bort (1855-1913) in 1902 after years of atmospheric measurements with unmanned balloons. He found that at altitudes above 8-10 km the temperature did not decline further.  He called the region of more constant temperature maintained by the ozone absorption of Solar UVR the “stratosphere” and the region below it the “troposphere.”  The tropopause is the region where the temperature remains constant before increasing in the stratosphere.  Teisserenc’s balloons only reached the tropopause and did advance into the stratosphere.  From: Crutzen (2000).

[9] At Oxford G.M.B. Dobson (1889-1976) together with F.A. Lindemann (1886-1957) (later Lord Cherwell) studied meteor trails from which they deduced the temperature profile above the troposphere was not constant.  Dobson followed on earlier work of Charles Fabry (1867-1945) and Henri Buisson (1873-1944) and measured ozone by observing its absorption in the Solar ultraviolet spectrum.  He was conferred the title of Oxford Professor in 1945, and his work with Alan Brewer led to the Brewer-Dobson Circulation model for the stratosphere.  From: http://www-atm.physics.ox.ac.uk/user/barnett/ozoneconference/dobson.htm. and other sources.

[10] The official name for this treaty is The Montreal Protocol on Substances That Deplete the Ozone Layer.  It was originally signed in 1987 and substantially amended in 1990 and 1992.  The Vienna Convention for the Protection of the Ozone Layer (1985) established the framework for the later Montreal Protocol.  From: http://www.ciesin.org/TG/PI/POLICY/montpro.html

[11] Halons are hydrocarbon compounds containing a combination of fluorine, chlorine, or bromine substituted for some or all of the hydrogen atoms.  They are mainly used in fire extinguishers.  Carbon tetrachloride was formally used as an aerosol can propellant, a solvent, a cleaning fluid, and in fire extinguishers. It is carcinogenic and can cause liver, kidney, and nervous system damage.  Methyl chloroform is used as a solvent for adhesives and for metal degreasing as well as a dry cleaning agent.

Essay posted Sunday 11 March 2007

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