Anaesthetic gases make small contribution to greenhouse effect
The gases used to knock out surgery patients are accumulating in the Earth’s atmosphere and making a small contribution to climate change, according to scientists who have detected the compounds as far afield as Antarctica.
Over the past decade, concentrations of desflurane, isoflurane and sevoflurane have been rising globally and are extra potent in their greenhouse-gas effects, says Martin Vollmer and a team of atmospheric chemists at the Swiss Federal Laboratories for Materials Science and Technology in a new paper published in Geophysical Research Letters.
On a kilogram-per-kilogram basis, desflurane is much more potent than carbon dioxide, with 1kg of desflurane being equivalent to 2500kg of carbon dioxide in terms of its greenhouse warming potential, although carbon dioxide is a billion times more abundant, explained lead author Vollmer.
The team reported the 2014 atmospheric concentration of desflurane as 0.30 parts per trillion (ppt), with isoflurane, sevoflurane and halothane measured at 0.097 ppt, 0.13 ppt and 0.0092 ppt, respectively. Nitrous oxide was not included in the study because it has many sources other than anaesthetics.
The researchers obtained their numbers by collecting samples of air from remote sites in the Northern Hemisphere since 2000, as well as aboard the icebreaker research vessel Araon during an expedition in the North Pacific in 2012 and at the South Korea Antarctic station King Sejong in the South Shetland Islands. They have also been tracking the anaesthetics since 2013 in two-hourly measurements at a high-altitude observatory at Jungfraujoch, Switzerland, and from ongoing air sampling from a rooftop in a suburb of Zurich.
To turn the air samples into global emissions estimates, the data were combined with a two-dimensional computer model of atmospheric transport and chemistry. The results, the first ‘top-down’ estimates of how many tonnes of each anaesthetic were released into the atmosphere in 2014, will now be compared with ‘bottom-up’ estimates of atmospheric concentrations by other researchers, based on factors such as how much of each gas is sold annually, how much typically escapes through operating room vents and how much is not metabolised by patients.
Vollmer, M., Rhee, T.S., Rigby, M., et al. (2015) Modern inhalation anesthetics: Potent greenhouse gases in the global atmosphere. Geophys. Res. Lett. Doi: 10.1002/2014GL062785