Climate change is one of the biggest issues facing the world, with a recent WHO report estimating it will cause ~250,000 additional deaths per year from 2030 to 2050.1 Coordinated, evidence-based efforts from individuals, institutions, and governments around the world are needed to address the severe ecological and health effects of global warming. One of the main driving forces behind climate change is the emission of greenhouse gases (GHGs), including waste anesthetic gases (WAGs). Excluding those used in dental, laboratory, and veterinary medicine, volatile anesthetics contribute the equivalent of 5.6 million tons of carbon dioxide to US GHG emissions.2 While WAGs contribute a much smaller portion of GHG emissions compared to the burning of fossil fuels in industries such as transportation and agriculture, minimizing the release of volatile anesthetics into the atmosphere is a step closer to reducing the detrimental effects of climate change. As such, it is important to understand the effects of volatile anesthetics on the climate.
Of the volatile anesthetics, the most widely used in clinical practice are N2O, desflurane, sevoflurane, and isoflurane. N2O and halogenated gases that contain bromine or chlorine, such as isoflurane and halothane, can diminish atmospheric ozone and thereby reduce the ultraviolet radiation-shielding effect of the ozone layer.3 While halogenated gases that lack chlorine or bromine, including sevoflurane and desflurane, do not catalytically destroy ozone, they can absorb and reduce outgoing infrared thermal energy, which is the defining characteristic of a GHG. During clinical operation, volatile anesthetics undergo little metabolism by the body and are largely eliminated via exhalation, increasing the risk of being released into the atmosphere where they function as GHGs.
Of the three most used fluorinated gases, sevoflurane has the shortest atmospheric lifetime (1-5 years), compared to isoflurane (3-6 years) or desflurane (9-21 years). Another important factor when comparing the climate effects of different volatile anesthetics is their global warming potential (GWP) value, which considers the radiative and atmospheric properties of a particular agent and is assessed in terms of CO2 emissions. Overall, GHG emissions from desflurane are 15 times more damaging than those from sevoflurane and 20 times more harmful than those from isoflurane. An Australian study confirmed the disproportionate contribution of desflurane to GHG emissions. While sevoflurane and isoflurane respectively contributed 17% and 6% to total annual anesthesia GHG emissions in 2011, desflurane contributed nearly 78%.4 The 100-year GWP for desflurane was calculated to be 893 CO2 equivalents/kg, compared to 48 for sevoflurane and 191
for isoflurane. To better understand the meaning of these GWP values, a US-based study contextualized the numbers by estimating 1 hour of desflurane anesthesia is equivalent to driving 235–470 miles in a standard automobile, while 1 hour of isoflurane or sevoflurane equates to driving 20–40 or 18 miles, respectively.5 The continued use of N2O as a carrier gas for volatile anesthetics during inhalation only further exacerbates the negative impacts of these agents.6
The emission of waste anesthetic gases is a significant contributor to total global greenhouse gas emissions and climate change. The use of volatile anesthetics, especially the halogenated gases desflurane, isoflurane, halothane, and sevoflurane, play a small but significant role in global warming. To reduce these emissions, it is recommended healthcare practitioners choose lower-GWP anesthetic agents to mitigate the environmental and health impacts of global warming. With the ever-increasing rates of surgeries and healthcare procedures, it is crucial that global leaders take steps to minimize these harmful emissions to safeguard both planetary and public health for future generations.
References
1. Climate Change. World Health Organization. 12 October 2023. https://www.who.int/news-room/fact-sheets/detail/climate-change-and-health
2. Varughese, Shane, and Raza Ahmed. “Environmental and Occupational Considerations of Anesthesia: A Narrative Review and Update.” Anesthesia & Analgesia, Apr. 2021. https://doi.org/10.1213/ANE.0000000000005504
3. Laboratory (CSL), NOAA Chemical Sciences. NOAA CSL: Scientific Assessment of Ozone Depletion: 2010. https://csl.noaa.gov/assessments/ozone/2010/twentyquestions/
4. Weinberg, L., et al. “Changing Patterns in Volatile Anaesthetic Agent Consumption over Seven Years in Victorian Public Hospitals.” Anaesthesia and Intensive Care, vol. 42, no. 5, Sept. 2014, pp. 579–83. https://doi.org/10.1177/0310057X1404200506
5. Ryan, Susan M., and Claus J. Nielsen. “Global Warming Potential of Inhaled Anesthetics: Application to Clinical Use.” Anesthesia & Analgesia, vol. 111, no. 1, July 2010, pp. 92–98. https://doi.org/10.1213/ANE.0b013e3181e058d7
6. Sherman, Jodi, et al. “Life Cycle Greenhouse Gas Emissions of Anesthetic Drugs.” Anesthesia & Analgesia, vol. 114, no. 5, May 2012, pp. 1086-90. https://doi.org/10.1213/ANE.0b013e31824f6940
