ATMOSPHERIC CHEMICAL-REACTIVITY AND OZONE-FORMING POTENTIALS OF POTENTIAL CFC REPLACEMENTS

The Montreal Protocol will lead to the eventual phaseout of the produc tion of chlorofluorocarbons (CFCs) and other halogenated organic compo unds that are implicated in the depletion of stratospheric ozone. Hydr ochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) have been d eveloped as potential ''in-kind'' replacement compounds. To ensure tha t these compounds are acceptable, industry and regulatory agencies are assessing the safety, toxicology, and environmental impact of the HCF Cs and HFCs before widespread production is commenced. One of the envi ronmental issues concerns the contribution that the HCFCs and HFCs mak e to photochemical ozone production. Photochemical ozone creation pote ntials (POCPs) have been calculated using a photochemical trajectory m odel. The POCPs of the HCFCs and HFCs are low, indicating that these c ompounds do not have a large potential to contribute to ground-level o zone formation. This results from their low reactivity compared to the other, more reactive, organic compounds present during a photochemica l episode. HCFCs and HFCs also contribute to stratospheric ozone deple tion and climate change. While the relative importance of the compound s within these issues can be defined with some certainty, our understa nding of how to weigh the relative importance of the different issues is not sufficiently well developed to assess with any degree of certai nty the benefits or the harm that might result from switching to the u se of HCFCs and HFCs.