Ozone damaging potential

Identification of alternative propellants likely to be free of ozone-damaging potential and global wanning effects... 

Table 1 lA presents tabulations of the safety of important refrigerants, but this list does not include aU available refrigerants. Table 11-5 summarizes a limited list of comparative hazards to life of refrigerant gas and vapor. The current more applicable refrigerants from the m or manufacturers of the CFC and HCFC refrigerants and their azeotropes/ blends/mrxtures are included, but the list excludes the pure hydrocarbons such as propane, chlorinated hydrocarbons such as methyl chloride and others, inorganics, ammonia, carbon dioxide, etc. See Table 11-6. The CFC compounds have a longer and more serious ozone depletion potential than the HCFC compounds, because these decompose at a much lower atmospheric level and have relatively short atmospheric lifetimes therefore, they do less damage to the ozone layer. Table 11-7 summarizes alternate refrigerants of the same classes as discussed previously. Table 11-8 correlates DuPont s SUVA refrigerant numbers to the corresponding ASHRAE numbers.

Stratospheric ozone Emission of ozone-depleting compounds (CFCs, Halons) Chemical reaction release of C1 and Br in stratosphere Catalytic destruction of ozone in stratosphere Skin and crop damage, damage to materials Ozone Depletion Potential (ODP)... 

Within the Montreal Protocol treaty, chlorofluorocarbons (CFCs) were broken up into several groups. Of primary importance was group 1 of annex A of the treaty, shown in Table 9.1. These CFCs are deemed to be more detrimental to the ozone layer on the basis of their ODP values. The ozone depletion potential is the relative amount of damage that a particular chemical causes to the ozone layer relative to R-ll (trichlorofluoromethane), which has an ozone depletion potential of 1.0. 

As can be seen from Table 9.2, ozone depletion values are zero for all compounds with the exception of R12. As stated earlier, the ozone depletion potential is the relative amount of damage that the particular chemical causes to the ozone relative to R-ll (Figure 9.2). Figure 9.3 shows the global warming impact of various refrigerant... 

It should be emphasised that the size of loss will be highly dependent upon the climate and possibly upon soil factors. The variations in the former, together with pest/fungal attack, etc., are likely to mask air pollutant effects. Nevertheless it is apparent that crop damage potential from acid pollutant/ozone may well be significant in almost all EEC Member States. 

The other global environmental problem, stratospheric ozone depletion, was less controversial and more imminent. The U.S. Senate Committee Report supporting the Clean Air Act Amendments of 1990 states, Destruction of the ozone layer is caused primarily by the release into the atmosphere of chlorofluorocarbons (CFCs) and similar manufactured substances—persistent chemicals that rise into the stratosphere where they catalyze the destruction of stratospheric ozone. A decrease in stratospheric ozone will allow more ultraviolet (UV) radiation to reach Earth, resulting in increased rates of disease in humans, including increased incidence of skin cancer, cataracts, and, potentially, suppression of the immune system. Increased UV radiation has also been shown to damage crops and marine resources."... 

Another area of potential interest is in refrigerator liners. The move away from the ozone-layer-damaging chlorofluorocarbons (CFCs) to HCFCs in the USA and pentane/cyclopentane blends in Europe has not been without problems. These newer materials have an adverse effect on ABS whereas the nitrile resin appears satisfactory, if more expensive. 

The question of the fate of chlorofluorocarbons upon their release into the atmosphere IS of great interest at present because of the potential damage to the earth s protective ozone layer caused by the reaction of ozone with photochemically generated chlorine atoms... 

The reported potentiation by ozone of the membrane damage produced by the indirect pathway of complement d might also play a role if it occurs in vivo, inasmuch as this complement pathway apparent mediates the allergin-reagin-induced release of histamine. in view of... 

Goldstein, B. D., L. Y. Lai, and R. Cuzzi Spada. Potentiation of complement-dependent membrane damage by ozone. Arch. Environ. Health 28 40-41, 1974. 

Ultraviolet (UV) rays Radiation from the sun that can be useful or potentially harmful. UV rays from one part of the spectrum (UV-A) enhance plant life. UV rays from other parts of the spectrum (UV-B) can cause skin cancer or other tissue damage. The ozone layer in the atmosphere partly shields us from ultraviolet rays reaching the Earth s surface. 

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