Ozone-depleting chemicals

An important effect of air pollution on the atmosphere is change in spectral transmission. The spectral regions of greatest concern are the ultraviolet and the visible. Changes in ultraviolet radiation have demonstrable adverse effects e.g., a decrease in the stratospheric ozone layer permits harmful UV radiation to penetrate to the surface of the earth. Excessive exposure to UV radiation results in increases in skin cancer and cataracts. The worldwide effort to reduce the release of stratospheric ozone-depleting chemicals such as chlorofluorocarbons is directed toward reducing this increased risk of skin cancer and cataracts for future generations. 

Tonnage of air emissions, water emissions and liquid and solid effluent and tonnage of hazardous materials released into the environment. These two measures are related to one another. However, the first measure relates the total effluent, including nonpolluting materials. The second measure looks only at the tonnage of hazardous materials contained in the total effluent. Both measures can be important indicators. For example, for solid waste it is important to know the total volume of material for disposal and different upstream treatment techniques may affect the total volume. However, for ozone depleting chemicals, only the quantity of these gases is important and other components such as water vapor may be irrelevant. 

New Stricter Environmental Standards based on UN Protocols Kyoto (GHGs) Montreal (ozone-depleting chemicals CFCs, etc) (e.g., Canada s New Model Energy Code for Housing that reduces GHGs). 

Many pulp and paper facilities operate industrial process refrigeration units such as chillers for chlorine dioxide plants. For those units that utilize ozone-depleting chemicals, such as chlorofluo-rocarbons (CFCs), facilities are required under Title VI to follow leak repair requirements. 

Single-stage chlorine refrigeration system (ammonia/carbon dioxide/chlorine) with no use of ozone-depleting chemicals. 

Uranium production does have a notable impact on ozone depletion. The Environmental Protection Agency s (EPA) Toxic Release Inventory showed that in 1999, the nation s two commercial nuclear fuel-manufacturing plants released 88% of the ozone-depleting chemical CFC-11 by industrial sources in the U.S. and 14% of the discharges in the whole world. 

The phasing out of CFCs and other ozone-depleting chemicals has given rise to... 

Stratospheric ozone depletion—one relatively easily controllable class of trace gases—ozone depleting chemicals (ODCs), principally chloroflurocar-bons (CFCs)—with relatively well quantified risks... 

Despite the growth of HCFCs, the National Oceanic Atmospheric Administration (NOAA) researchers data show that ozone-depleting chemicals in the atmosphere have declined overall about 3% since 1994. But that decrease is due almost entirely to a dramatic drop in the amount of methylchloroform, which was used as a cleaning solvent. Natural oxidation processes in the atmosphere remove methylchloroform so efficiently that its atmospheric concentration has been falling rapidly since production stopped. 

However, trichlorofluoromethane is an atmospheric ozone depletion chemical, and therefore, alternatives have been under investigation. There have been many other agents used for flash spinning PE to either minimize or eliminate the potential for ozone depletion. 

Generally considered to be among the least toxic of the alkyl halides, 1,1,1-trichloroethane was once produced at levels of several hundred million kilograms per year. However, it is persistent in the atmosphere and is a strong stratospheric ozone-depleting chemical, so production has been severely curtailed and there is now little reason for concern over its toxicity. 

The Montreal Protocol is an agreement between industrialized nations to reduce the amount of ozone-depleting chemicals released into the atmosphere. Do research to discover answers to these questions ... 

Based on predictions of the effect of CFCs on the ozone layer, in 1987 a previously unprecedented step was taken when many countries signed the UN Montreal protocol specifying the control and phase-out of these ozone-depleting chemicals. Since that time the protocol has been modified in order to speed up the schedule and extend the range of chemical covered to further lessen the effect of these chemicals (see Figure 27). One of the factors that lead to more rapid world action on CFCs was the discovery of the so-called Antarctic ozone hole. 

The environmental hazard posed by this series of reactions is that the level of ultraviolet radiation reaching the earth would be expected to increase as more and more ozone molecules are destroyed. Ultraviolet radiation has been implicated in a number of biological problems for plants, animals, and humans, including an increase in skin cancer and in eye problems. In response to this threat, most of the world s nations have agreed to reduce the amount of Freons, CFCs, and other ozone-depleting chemicals produced and sold each year. 

Brown MS. Hart A. 1992. Reducing the use of ozone depleting chemicals the Irvine California ordinance. J Air Waste Manage Assoc 42(4) 429-432. 

In recent years, it has become possible to extrapolate accurately using detailed chemical kinetic models to predict quantitatively the behavior of some rather complicated chemical systems. The most famous examples of this success are the detailed atmospheric chemistry models whose predictions underlie the Montreal Protocol on ozone-depleting chemicals. However, these atmospheric chemistry models were developed through a huge international effort over several decades, based heavily on a large number of laboratory experiments. Much more rapid and efficient methods of model development are required for detailed predictive chemical kinetics to become a practical everyday design tool for chemical engineering. 

Special Topic 7-1 Green Chemistry—Substitutes for Chlorofluorocarbons describes substitutes for chlorofluorocarbons, and Special Topic 7.2 Other Ozone-Depleting Chemicals describes other ozone-depleting chemicals. 

Special Topic 7.2 Other Ozone-Depleting Chemicals... 

---