Substance Abuse: Carbon Tetrachloride and the Ozone Layer

Each year, similar to 200000 tonnes of carbon tetrachloride are produced and consumed as a solvent, a starting material for synthesis, or in standard methods of analysis. Because it is an ozone-depleting substance, this information is reported on an annual basis to the Montreal Protocol, under which it is a controlled' substance. Replacing emissive uses of carbon tetrachloride with ozone-friendly chemicals is proceeding slowly. One example is the use of tetrachloroethylene as a replacement for carbon tetrachloride in oil and grease analysis by infrared spectroscopy. Overall, however, there is more carbon tetrachloride in the upper atmosphere than can be accounted for in terms of known uses and emissions. The discrepancy is the subject of intensive and repeated investigation by atmospheric scientists.