Refrigerants and ozone lawyer: A brief loook about the history.

A  brief look about the History: Three Pioneers

 By Rolando Delgado Castillo

   Versión en español                                                                            English version

Dobson: Pioneer in the determination of ozone atmospheric

Gordon Miller Bourne Dobson (1889 - 1976) was an experimentalist who devoted much of his life to study of atmospheric ozone. The results were to be of great importance in leading to an understanding of the structure and circulation of the stratosphere.

He came to Oxford in 1920 to take up the position of University Lecturer in Meteorology,  and Dobson worked on studies of meteor trails, from which he deduced that the temperature profile above the tropopause was not constant - as simple theory would predict and the name 'stratosphere' implies - but rather that there was a region where temperature increased substantially with height. Dobson inferred correctly that the cause of the warm stratosphere was heating by the absorption of ultraviolet solar radiation by ozone, and he set out to make measurements of the amounts and their variability. 

The first spectrograph was built in the summer of 1924 at Dobson's laboratory and workshop in a hut built for the purpose in the grounds of his home, Robin Wood, Boars Hill. Extensive measurements during 1925 established the main features of the seasonal variation of ozone, the maximum in the spring and the minimum in the autumn, and also demonstrated the close correlation between ozone amount and the meteorological conditions in the upper troposphere and lower stratosphere. By the end of 1929, therefore, the main feature of the variation of the ozone amount with synoptic conditions, with latitude and with season had been established.


In the early 1930s Dobson became concerned with the study of atmospheric pollution,  and under his guidance reliable methods were developed for the measurement of smoke, and deposited matter.


After World War II, international ozone work became organised under the International Ozone Commission which was set up in 1948 at the Oslo meeting of the International Union of Geodesy and Geophysics. The first Secretary was Sir Charles Normand who in 1947 had joined Dobson in Oxford. The International Geophysical Year in 1956 brought a large increase in the number of ozone instruments required. The most interesting result which came out of the I.G.Y. measurements was the discovery of the annual variation of ozone at Halley Bay in Antarctica showing a sudden rise in November - very different behaviour from the northern hemisphere.


Dobson retired from his University readership in 1950 and from his university demonstratorship in 1956, but work on atmospheric ozone continued all through his retirement years. His last paper was written in 1973, 62 years after his first one, and his last observation of atmospheric ozone was made the day before he had the stroke from which he died six weeks later. The Dobson Ozone Spectrometer is still in use world-wide with a network of over 150 instruments making daily observations. 


Oxford University (2003):  Short Biography of  G.M.B. Dobson


Thomas Midgley Jr: A great inventor


Thomas Midgley Jr (1889 - 1944) was an American mechanical engineer, formed of self-taught way in chemistry that represents a forced reference to demonstrate the importance to evaluate the possible impact of any new technology that demands the massive use of chemical agents. 


Midgley faced in the second decade of the century two problems created by the mighty American industry.  The activity of the transport demanded the increase of the efficiency in the combustion process by reducing irregular detonation that took place during the operation of motor.  Midgley supposed that using certain additive could improve the qualities of gas to act like anti-detonation.  First on approval of test and error and soon following certain tendencies in the periodic table, in 1921, while he worked in the research laboratory of the General Motors, discovered that tetraethyl lead was an anti-detonation ideal.  Two years later was commercialized ethylated gasoline in the United States. 


The toxicity properly was not evaluated and the contamination extended for more than 60 years, being impossible an objective evaluation from the impact that could cause mainly in the infantile population, in which the lead can cause delays in the development, upheaval of the memory and problems in hearing. 


A second problem appeared with the substances that were used like refrigerants in the decade of the 20 (ammoniac, sulfur dioxide and methyl chloride).  Between the undesirable qualities presented by these substances, mainly for the expansion of the domestic refrigeration, were the toxicity and inflammability.  Dramatic accidents took place by the escapes of the units of refrigeration in the homes, mainly in the nocturnal schedule.  Looking for a good substitute for these refrigerants Midgley developed to the tetrafluoromethane and the dichlorodifluoromethane (but late call Freon).


In 1930 Thomas Midgley demonstrated before the American Chemical Society the safe physical properties of Freon inhaling deeply and exhaling toward the flame of a candle, which was extinguished.  Thus Midgley verified that the product was neither toxic nor inflammable either.  The generation of ideal refrigerating agents was into the manufacturers hands.  New applications were found for the chlorofluorocarbons, among them those to act like propellants of all type of commercial aerosol.  A new danger was hung over one of the protective substances that the nature had created allowing the development of the life in the Earth.  Midgley was 51 years old when he contracted polio and left affected severely.  Like inventor he developed a complex mechanism of aid to its disturbance.  Accidentally, he died victim of his own invention, 4 years later, strangled.


Bellis Mary (2005): The History of Freon.


US Hall of Fame (2002): Thomas Midgley Jr.


Mario Molina: Concerns of the Scientific Community  


Four decades later of the Midgley’s patent by reclaiming chlorofluorocarbons like new refrigerating agents, scientists of the University of California, Irvine, F. Sherwood (1927- ) and the Mexican - American Mario Molina (1943- ) determined, after an exhaustive study, that  chlorofluorocarbons used massively like propellants in all type of "spray" and like refrigerants, have potential to destroy the ozone layer. In effect, in recent years, has been confirmed the ozone lawyer depletion in different latitudes from the planet. 


This ozone lawyer depletion causes an increase of the ultraviolet radiation levels that it penetrates in the atmosphere and it affects the surface of the planet.  Filtered ultraviolet radiation can be responsible for the increase of the cancer frequency in the skin observed in the Nordic countries, the elevation of the suffering of vision upheavals, as well as the reduction of plancton, first link in the fish nourishing chain.


The importance conceded to these problems by the scientific community is expressed by the Nobel Prize granted to Sherwood, Molina and to Dutch chemist Paul Crutzen (1933- ) in 1995.  Crutzen had indicated that the nitrogen oxide could cause the degradation of the stratospheric ozone layer, since when triggering a mechanism in chain, a low concentration of nitrogen oxide would be translated in a significant consumption of ozone.


Mexican - American, Mario J. Molina, Prize Nobel of Chemistry in 1995, confess in his autobiography that during his first years in Berkeley felt a deep rejection to the chemical possibility of using the high power laser to produce arms.  He wished at that time developed an investigation project that were useful to the society, and get it.  The 28 of June of 1974 published, together with his advisory F. Sherwood Rowland, in the Nature Magazine a first report alerting to the scientific community and the public opinion about the dangers in that was the stratospheric ozone layer.  Image:  © The Nobel Foundation 


In 1976 the Program of United Nations for the Environment Protection (UNEP) calls to a International Conference to discuss an universal answer to the ozone problem.  In 1985 was signed in Austria "the Convention of Vienna for the protection of ozone lawyer¨ but this was not accompanied by a binding protocol. Two years later in Canada was signed "Protocol of Montreal on the substances that degrade the ozone layer". This protocol, legally binding, is approved by 24 countries, being Canada between the signatory countries. Successive international meeting have been organized by UN to discuss and to take actions in agreement with the updated information from the experts on the effect of the ozone layer depletion. 



Molina Mario J. (1995): Autobiography.


Environment Canada’s WWW Site (2002): Stratospheric Ozone Action: An Historical Overview.


PNUMA (2000): Protocolo de Montreal. ( En su forma ajustada y o enmendada en Montreal 1987, Londres, 1990, Copenhague, 1992, Viena, 1995, Montreal, 1997, Beijing, 1999).