Volatile anaesthetics and the atmosphere: atmospheric lifetimes and atmospheric effects of halothane, enflurane, isoflurane, desflurane and sevoflurane

The atmospheric lifetimes of the halogenated anaesthetics halothane, enflur ane, isoflurane, desflurane and sevoflurane with respect to reaction with t he hydroxyl radical (OH) and UV photolysis have been determined from observ ations of OH reaction kinetics and UV absorption spectra. Rate coefficients for the reaction with OH radicals for all halogenated anaesthetics investi gated ranged from 0.44 to 2.7 x 10(-14) cm(3) molec(-1) s(-1). Halothane, e nflurane and isoflurane showed distinct UV absorption in the range 200-350 nm. In contrast, no absorption in this wavelength range was detected for de sflurane or sevoflurane. The total atmospheric lifetimes, as derived from b oth OH reactivity and photolysis, were 4.0-21.4 yr. it has been calculated that up to 20% of anaesthetics enter the stratosphere. As a result of chlor ine and bromine content, the ozone depletion potential (ODP) relative to ch lorofluorocarbon CFC-11 varies between 0 and 1.56, leading to a contributio n to the total ozone depletion in the stratosphere of approximately 1% for halothane and 0.02% for enflurane and isoflurane. Estimates of the greenhou se warming potential (GWP) relative to CFC-12 yield values of 0.02-0.14, re sulting in a relative contribution to global warming of all volatile anaest hetics of approximately 0.03%. The stratospheric impact of halothane, isofl urane and enflurane and their influence on ozone depletion is of increasing importance because of decreasing chlorofluorocarbons globally. However, th e influence of volatile anaesthetics on greenhouse warming is small.