The
gases used to knock out surgery patients are accumulating in Earth's
atmosphere, where they make a small contribution to climate change, report
scientists who have detected the compounds as far afield as Antarctica. Over
the past decade, concentrations of the anesthetics desflurane, isoflurane and
sevoflurane have been rising globally, the new study finds.
Like
the well-known climate warmer carbon dioxide, anesthesia gases allow the
atmosphere to store more energy from the Sun. But unlike carbon dioxide, the
medical gases are extra potent in their greenhouse-gas effects.
One
kilogram (2.2 pounds) of desflurane, for instance, is equivalent to 2,500
kilograms (5,512 pounds) of carbon dioxide in terms of the amount of greenhouse
warming potential, explained Martin Vollmer, an atmospheric chemist at the
Swiss Federal Laboratories for Materials Science and Technology in Dubendorf,
Switzerland, who led the new study. "On a kilogram-per-kilogram basis,
it's so much more potent" than carbon dioxide, he said.
In
a new scientific paper, Vollmer and his colleagues report the 2014 atmospheric
concentration of desflurane as 0.30 parts per trillion (ppt). Isoflurane,
sevoflurane and halothane came in at 0.097 ppt, 0.13 ppt and 0.0092 ppt,
respectively. Carbon dioxide -- which hit 400 parts per million in 2014 -is a
billion times more abundant than the most prevalent of these anesthetics. The
team did not include the common anesthesia nitrous oxide in the study because
it has many sources other than anesthetics. The team's anesthesia-gas findings
have been published online in Geophysical Research Letters, a journal of
the American Geophysical Union.
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 anesthetics 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, Switzerland.
To
turn these air samples into their global emissions estimates, the data were
combined with a two-dimensional computer model of atmospheric transport and
chemistry. The results are the first so-called top-down estimates--based on
actual atmospheric measurements--of how many metrics tons of each anesthetic
were released into the atmosphere in 2014. That can now be compared to
"bottom-up" estimates by other researchers, which estimate
atmospheric concentrations 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 metabolized by patients.
Although
anesthetics are small players in overall human-generated greenhouse emissions,
they are a growing matter of concern to many in the health-care industry.
Anesthesia gas abundances are growing and should not be overlooked, said Yale
University School of Medicine anesthesiologist Jodi Sherman, a reviewer of the
GRL paper.
"Health
care in and of itself in the U.S. is one of the worst polluting
industries," she explained. "It generates 8 percent of U.S.
greenhouse gases according to one study. Add to this the fact that climate
change has been recognized by the World Health Organization as the number one
health issue of the 21st century, and it behooves us to do a better job with
emissions."
Anesthesia
gases are something that the health care industry can easily do something
about, Sherman added. Dropping desflurane, for instance, would make sense
because it is the most potent greenhouse gas of the bunch. Not all
anesthesiologists agree with that strategy, however.
"What
the report fails to note is that a major factor determining the environmental
effect is the manner in which the anesthetics are used," said
anesthesiologist Edmond Eger of the University of California at San Francisco.
"Many anesthetists deliver sevoflurane or isoflurane in a two -- three
liters per minute flow but deliver desflurane in a lower flow -- 0.5 to one
liter per minute .... Some believe that desflurane has clinical advantages that
argue for its continued use."
"There's
nothing unique about desflurane that we can't do with other drugs,"
Sherman countered. "Desflurane we could live without, and every little bit
makes a difference."
Story
Source:
The
above story is based on materials provided by American
Geophysical Union. Note: Materials may be edited for content
and length
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