Assessing the potential climate impact of anaesthetic gases.

There is increasing concern within the health-care community about the role care delivery plays in environmental degradation, sparking research into how to reduce pollution from clinical practice. Inhaled anaesthetics is a particular research area of interest for two reasons. First, several gases are potent greenhouse gases, and waste gas is mostly emitted directly to the environment. Second, there are options to reduce gas waste and substitute medications and procedures with fewer embodied emissions while delivering high-quality care. Performance improvements are contingent on a proper understanding of the emission estimates and climate metrics used to ensure consistent application in guiding mitigation strategies and accounting at various scales. We review the current literature on the environmental impact and the estimation of the potential climate forcing of common inhaled anaesthetic drugs: desflurane, sevoflurane, isoflurane, methoxyflurane, and nitrous oxide.

Correction: Atmospheric chemistry of CF3CN: kinetics and products of reaction with OH radicals, Cl atoms and O3.

Correction for 'Atmospheric chemistry of CF3CN: kinetics and products of reaction with OH radicals, Cl atoms and O3' by Mads Peter Sulbaek Andersen et al., Phys. Chem. Chem. Phys., 2022, 24, 2638-2645, https://doi.org/10.1039/D1CP05288H.

The science behind banning desflurane: A narrative review.

Potent inhaled anaesthetics are halogenated hydrocarbons with a large global warming effect. The use of fluorinated hydrocarbons (most are not anaesthetics) are being restricted but volatile anaesthetics have been exempted from legislation, until now: the EU has formulated a proposal to ban or at least severely restrict the use of desflurane starting January 2026. This narrative review addresses the implications of a politics-driven decision - without prior consultation with major stakeholders, such as the European Society of Anaesthesiology and Intensive Care (ESAIC) - on daily anaesthesia practice and reviews the potential scientific arguments that would support stopping the routine use of desflurane in anaesthetic practice. Of note, banning or severely restricting the use of one anaesthetic agent should not distract the user from sensible interventions like reducing fresh gas flows and developing technology to capture and recycle or destroy the wasted potent inhaled anaesthetics that we will continue to use. We call to join efforts to minimise our professional environmental footprint.

Atmospheric chemistry of CF3CN: kinetics and products of reaction with OH radicals, Cl atoms and O3.

Long path length FTIR-smog chamber techniques were used to study the title reactions in 700 Torr of N2, oxygen or air diluent at 296 ± 2 K. Values of k(Cl + CF3CN) = (2.43 ± 0.33) × 10-15 and k(OH + CF3CN) = (4.61 ± 0.34) × 10-15 cm3 molecule-1 s-1 were measured. There was no discernible reaction of CF3CN with O3 and an upper limit of k(O3 + CF3CN) ≤ 7.9 × 10-24 cm3 molecule-1 s-1 was established. The IR spectra of CF3CN and CF3CF2CN are reported. The atmospheric lifetime of CF3CN is determined by the reaction with OH and is approximately 6.9 years. Reaction of CF3CN with Cl atoms in a chamber study gives (Z-) and/or (E-) CF3CClNCl and CF3C(O)Cl as major primary products. Under environmental conditions, the OH radical initiated oxidation gives COF2 in a yield of (96 ± 8)%. The global warming potential for CF3CN is estimated as 1030 for a 100 year time horizon.

Atmospheric Chemistry of CH3OCF2CHF2.

Fourier transform infrared spectroscopy has been used to follow the reaction of CH3OCF2CHF2 with either Cl or OH radicals within a photoreactor. Rate constants of k(OH + CH3OCF2CHF2) = (2.25 ± 0.60) × 10-14 cm3 molecule-1 s-1 and k(Cl + CH3OCF2CHF2) = (2.50 ± 0.39) × 10-13 cm3 molecule-1 s-1 were determined at 296 ± 2 K. Theoretical and experimental investigation of the Cl + CH3OCF2CHF2 reaction identified the formation of two main products, HC(O)OCF2CHF2 and COF2. Chlorine (and OH) radicals react with CH3OCF2CHF2 by H-abstraction from either the -CH3 or -CHF2 site. Abstraction from the -CH3 site was determined to constitute at least 60%, as determined from the formation of the primary product, HC(O)OCF2CHF2, which can only form from this abstraction site. At longer reaction times, HC(O)OCF2CHF2 further reacts and the yield of COF2 approaches two, the maximum possible with the number of F atoms in the reactant. The atmospheric lifetime of CH3OCF2CHF2 with OH radicals was determined to be 1.4 years. The global warming potentials over 20-, 100-, and 500-year time horizons were estimated to be 325, 88, and 25, respectively.

Reflection on two Ambio papers by P. J. Crutzen on ozone in the upper atmosphere : This article belongs to Ambio's 50th Anniversary Collection. Theme: Ozone Layer.

We here reflect on two important articles on stratospheric ozone depletion written by P. J. Crutzen (1974) and P. J. Crutzen and D. H. Ehhalt (1977) in the early 1970s. These articles provide a clear description of the stratosphere and the most important chemical reactions involved in stratospheric ozone depletion. They present modeling results and provide recommendations for future research on stratospheric ozone depletion caused by chloro-fluoro-carbons, supersonic transport, nitrous oxide, and nuclear explosions. These two articles represent the beginning of a scientific era, which led to discovery of the Antarctic ozone hole and political action in the form of the Montreal Protocol and its amendments.

Trichloroacetyl chloride, CCl3COCl, as an alternative Cl atom precursor for laboratory use and determination of Cl atom rate coefficients for n-CH2[double bond, length as m-dash]CH(CH2)xCN (x = 3-4).

An investigation of CCl3COCl was conducted with the purpose of using the compound as an alternative Cl atom precursor in laboratory settings. CCl3COCl can be used with or without O2 as a source of Cl atoms and photolysis studies in air and N2 diluent displayed COCl2 and CO as being the major photolysis products. Relative rate studies were performed to determine the Cl atom rate coefficients for reaction with CH3Cl and C2H2 and the results were in agreement with literature values. Cl atom rate coefficients for reaction with n-CH2[double bond, length as m-dash]CH(CH2)3CN and n-CH2[double bond, length as m-dash]CH(CH2)4CN were determined as (2.95 ± 0.58) × 10-10 and (3.73 ± 0.60) × 10-10 cm3 molecule-1 s-1, respectively. CCl3COCl requires UV-C irradiation, so not all molecules are feasible for use in e.g. relative rate studies. Furthermore, it is recommended to perform experiments with O2 present, as this minimizes IR feature disturbance from product formation.

Theoretical study of hydroxyl radical (OH˙) induced decomposition of tert-butyl methyl ether (MTBE).

We have characterized the various pathways for OH radical (OH˙) induced decomposition of tert-butyl methyl ether (MTBE) and found an oxidative pathway that leads to complete degradation under the prerequisite that OH radicals are present in excess. A simple polarizable continuum model is used to predict the behavior in an aqueous medium and the behavior is unchanged compared to that in the gas phase. The computational study has also revealed some of the fundamental aspects of hydrogen transfer from asymmetric ethers; the ˙OH assisted hydrogen abstraction has a barrier when the reaction takes place at a distance from the heteroatom, that is, at the tert-butyl group, whereas hydrogen abstraction from the methyl group proceeds without a barrier. The addition of ˙OH to (CH3)3COCH2˙ also proceeds without a barrier, and so does hydrogen abstraction from the resulting adduct ((CH3)3COCH2OH) to form (CH3)3COCH(OH)˙. However, a barrier is yet again found in the hydrogen abstraction from the latter to form (CH3)3COCH[double bond, length as m-dash]O and yet again in the formation of the formyl radical (CH3)3COC[double bond, length as m-dash]O˙ by hydrogen abstraction. The latter is the last step before the final stage of complete oxidation of MTBE to form CO2.

Atmospheric Chemistry of Pentafluorophenol: Kinetics and Mechanism of the Reactions of Cl Atoms and OH Radicals.

Fourier transform infrared smog chamber techniques were used to study the kinetics and mechanisms of the reactions of Cl atoms and OH radicals with pentafluorophenol (C6F5OH) in 700 Torr total pressure of air or N2 diluent at 296 ± 2 K. Rate constants k(OH + C6F5OH) = (6.88 ± 1.37) × 10-12 cm3 molecule-1 s-1 and k(Cl + C6F5OH) = (2.52 ± 0.31) × 10-11 cm3 s-1 molecule-1 in 700 Torr air diluent were determined. In 700 Torr N2, the rate constant for the reaction of C6F5OH with Cl atoms is linearly dependent on the Cl atom concentration. Product studies on this reaction in both 700 Torr air and 700 Torr N2 diluent show the formation of nonconjugated products. The photolysis constant of C6F5OH was determined by 254 nm UV irradiation of a C6F5OH and CH3CHO mixture in 700 Torr air or N2 at 296 ± 2 K and yielded a photolysis rate constant of J(C6F5OH) = (2.83 ± 0.25) × 10-3 s-1. Results are discussed with respect to the atmospheric chemistry of other halogenated aromatic species.

Quantum Yields and N2O Formation from Photolysis of Solid Films of Neonicotinoids.

Neonicotinoids (NN), first introduced in 1991, are found on environmental surfaces where they undergo photolytic degradation. Photolysis studies of thin films of NN were performed using two approaches: (1) transmission FTIR, in which solid films of NN and the gas-phase products were analyzed simultaneously, and (2) attenuated-total-reflectance FTIR combined with transmission FTIR, in which solid films of NN and the gas-phase products were probed in the same experiment but not at the same time. Photolysis quantum yields using broadband irradiation centered at 313 nm were (2.2 ± 0.9) × 10-3 for clothianidin (CLD), (3.9 ± 0.3) × 10-3 for thiamethoxam (TMX), and (3.3 ± 0.5) × 10-3 for dinotefuran (DNF), with all errors being ±1 s. At 254 nm, which was used to gain insight into the wavelength dependence, quantum yields were in the range of (0.8-20) × 10-3 for all NNs, including acetamiprid (ACM) and thiacloprid (TCD). Nitrous oxide (N2O), a potent greenhouse gas, was the only gas-phase product detected for the photolysis of nitroguanidines, with yields of ΔN2O/ΔNN > 0.5 in air at both 313 and 254 nm. The atmospheric lifetimes with respect to photolysis for CLD, TMX, and DNF, which absorb light in the actinic region, are estimated to be 15, 10, and 11 h, respectively, at a solar zenith angle of 35° and 12, 8, and 10 h at a solar zenith angle of 15°.

Atmospheric chemistry of a cyclic hydro-fluoro-carbon: kinetics and mechanisms of gas-phase reactions of 1-trifluoromethyl-1,2,2-trifluorocyclobutane with Cl atoms, OH radicals, and O3.

Long path length FTIR-smog chamber techniques were used to study the title reactions in 700 Torr of N2 or air diluent at 296 ± 2 K. Values of k(Cl + 1-trifluoromethyl-1,2,2-trifluorocyclobutane (TFMTFCB)) = (1.16 ± 0.21) × 10-14 and k(OH + TFMTFCB) = (3.51 ± 0.88) × 10-14 cm3 molecule-1 s-1 were measured. No reactivity of TFMTFCB towards ozone was observed. The atmospheric lifetime of TFMTFCB is determined by the reaction with OH and is approximately 330 days. The chlorine initiated oxidation gives C(O)F2 and CF3C(O)F as the dominant products in yields of (92 ± 2)% and (89 ± 2)%, respectively. The OH radical initiated oxidation gives C(O)F2 and CF3C(O)F as the dominant products in yields of (91 ± 6)% and (84 ± 4)%, respectively. The GWP100 was calculated as 44. The atmospheric chemistry of the title compound, a cyclic halogenated alkane, is discussed in the context of other halogenated cyclo-alkanes.

Atmospheric chemistry of (Z)-CF3CH[double bond, length as m-dash]CHCl: products and mechanisms of the Cl atom, OH radical and O3 reactions, and role of (E)-(Z) isomerization.

The chemical mechanisms of the OH radical, Cl-atom and O3 initiated oxidation of (Z)-CF3CH[double bond, length as m-dash]CHCl were studied at 296 ± 1 K in 10-700 Torr air of N2/O2 diluent. Cl atoms add to the [double bond splayed left]C[double bond, length as m-dash]C[double bond splayed right] double bond: 12 ± 5% to the terminal carbon and 85 ± 5% to the central carbon. In 700 Torr of air the products are CF3CHClCHO, HCOCl, CF3COCl, CF3CHO, (E)-CF3CH[double bond, length as m-dash]CHCl, CF3C(O)CHCl2, and CF3CHClCOCl. The yield of (E) isomer was dependent on total pressure, but independent of O2 partial pressure; consistent with isomerization occurring via Cl atom elimination from the chemically activated rather than the thermalized CF3CHCHCl-Cl adduct. The rate constant for (Z)-CF3CH[double bond, length as m-dash]CHCl + Cl was measured at low pressure (10-15 Torr) and found to be indistinguishable from that determined at 700 Torr total pressure, whereas the low pressure rate constant for (E)-CF3CH[double bond, length as m-dash]CHCl was 36% smaller. G4MP2 ab initio calculations showed that the (E) isomer is 1.2 kcal mol-1 more stable than the (Z) isomer. Cl atom elimination from the adduct will preferentially form the (E) isomer and hence the rate of CF3CH[double bond, length as m-dash]CHCl loss will be more sensitive to pressure for the (Z) than the (E) isomer. Reaction of (Z)-CF3CH[double bond, length as m-dash]CHCl with OH radicals gives CF3CHO, HCOCl, (E)-CF3CH[double bond, length as m-dash]CHCl, and HCl. A significant chlorine atom elimination channel was observed experimentally, and supported by computational results. The oxidation products of the reaction of O3 with (Z)- and (E)-CF3CH[double bond, length as m-dash]CHCl were determined with no evidence of isomerization. The results are discussed with respect to the atmospheric chemistry and environmental impact of (Z)- and (E)-CF3CH[double bond, length as m-dash]CHCl.

Atmospheric chemistry of hexa- and penta-fluorobenzene: UV photolysis and kinetics and mechanisms of the reactions of Cl atoms and OH radicals.

Photochemical reactors were used to study the kinetics and mechanisms of reactions of Cl atoms and OH radicals with hexa- and penta-fluorobenzene (C6F6, C6F5H) in 700 Torr total pressure of N2, air, or O2 diluent at 296 ± 2 K. C6F6 and C6F5H undergo ring-opening following 254 nm UV irradiation, but with small quantum yields (φ < 0.03). Reaction of Cl atoms with C6F6 proceeds via adduct formation, while the reaction of Cl atoms with C6F5H proceeds via hydrogen abstraction and adduct formation. C6F6-Cl and C6F5H-Cl adducts decompose rapidly (k ∼ 105-106 s-1) reforming the reactants, and react with Cl atoms to form products. The fraction of adduct reacting with Cl atoms increases with steady state Cl atom concentration, resulting in an increasing apparent effective Cl atom rate constant. The rate constant for the H-abstraction channel for Cl + C6F5H is estimated at (7.3 ± 5.7) × 10-16 cm3 molecule-1 s-1. Establishment of the equilibrium between the adducts and the aromatic reactant + Cl occurs rapidly with equilibrium constants of K([adduct]/[aromatic][Cl]) = (1.96 ± 0.11) × 10-16 and (9.28 ± 0.11) × 10-17 cm3 molecule-1 for C6F6 and C6F5H, respectively. Reaction of the adducts with O2 occurs slowly with estimated rate constants of <7 and <4 × 10-18 cm3 molecule-1 s-1 for C6F6-Cl and C6F5H-Cl, respectively. The rate constants for reaction of OH radicals with C6F6 and C6F5H were determined to be (2.27 ± 0.49) × 10-13 and (2.56 ± 0.62) × 10-13 cm3 molecule-1 s-1, respectively. UV and IR spectra of C6F6 and C6F5H at 296 ± 1 K were collected and calibrated. Results are discussed in the context of available literature data for reactions of Cl atoms and OH radicals with halogenated aromatic compounds.

Atmospheric Chemistry of n-CH2═CH(CH2) xCN ( x = 0-4): Kinetics and Mechanisms.

Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure the kinetics of the reaction of n-CH2═CH(CH2) xCN ( x = 0-4) with Cl atoms, OH radicals, and O3: k(CH2═CHCN + Cl) = (1.03 ± 0.13) × 10-10, k(CH2═CHCH2CN + Cl) = (2.02 ± 0.35) × 10-10, k(CH2═CH(CH2)2CN + Cl) = (2.75 ± 0.45) × 10-10, k(CH2═CHCN + OH) = (4.21 ± 0.95) × 10-12, k(CH2═CHCH2CN + OH) = (1.55 ± 0.34) × 10-11, k(CH2═CH(CH2)2CN + OH) = (2.98 ± 0.64) × 10-11, k(CH2═CH(CH2)3CN + OH) = (3.34 ± 0.64) × 10-11, k(CH2═CH(CH2)4CN + OH) = (3.61 ± 0.85) × 10-11, k(CH2═CHCN + O3) = (2.55 ± 0.28) × 10-20, k(CH2═CHCH2CN + O3) = (1.17 ± 0.24) × 10-18, k(CH2═CH(CH2)2CN + O3) = (3.35 ± 0.69) × 10-18, k(CH2═CH(CH2)3CN + O3) = (4.07 ± 0.82) × 10-18, and k(CH2═CH(CH2)4CN + O3) = (7.13 ± 1.49) × 10-18 cm3 molecule-1 s-1 at a total pressure of 700 Torr of air or N2 diluents at 296 ± 2 K. CH2ClC(O)CN, HC(O)CN, HC(O)Cl, HCN, NCC(O)OONO2, and ClC(O)OONO2 were identified as products from the Cl initiated oxidation of CH2═CHCN. The product spectra were compared to experimental and theoretically calculated IR spectra. No products could be determined from the oxidation of n-CH2═CH(CH2) xCN ( x = 1-4). With the determined OH rate constants, the atmospheric lifetimes for n-CH2═CH(CH2) xCN ( x = 0-4) were estimated to be 66, 18, 9.3, 8.3, and 7.7 h, respectively. It was found that these unsaturated nitriles have no significant atmospheric environmental impact.

Atmospheric Chemistry of (CF3)2CF-C≡N: A Replacement Compound for the Most Potent Industrial Greenhouse Gas, SF6.

FTIR/smog chamber experiments and ab initio quantum calculations were performed to investigate the atmospheric chemistry of (CF3)2CFCN, a proposed replacement compound for the industrially important sulfur hexafluoride, SF6. The present study determined k(Cl + (CF3)2CFCN) = (2.33 ± 0.87) × 10-17, k(OH + (CF3)2CFCN) = (1.45 ± 0.25) × 10-15, and k(O3 + (CF3)2CFCN) ≤ 6 × 10-24 cm3 molecule-1 s-1, respectively, in 700 Torr of N2 or air diluent at 296 ± 2 K. The main atmospheric sink for (CF3)2CFCN was determined to be reaction with OH radicals. Quantum chemistry calculations, supported by experimental evidence, shows that the (CF3)2CFCN + OH reaction proceeds via OH addition to -C(≡N), followed by O2 addition to -C(OH)═N·, internal H-shift, and OH regeneration. The sole atmospheric degradation products of (CF3)2CFCN appear to be NO, COF2, and CF3C(O)F. The atmospheric lifetime of (CF3)2CFCN is approximately 22 years. The integrated cross section (650-1500 cm-1) for (CF3)2CFCN is (2.22 ± 0.11) × 10-16 cm2 molecule-1 cm-1 which results in a radiative efficiency of 0.217 W m-2 ppb-1. The 100-year Global Warming Potential (GWP) for (CF3)2CFCN was calculated as 1490, a factor of 15 less than that of SF6.

Atmospheric chemistry of Z- and E-CF3CH[double bond, length as m-dash]CHCF3.

The atmospheric fates of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 have been studied, investigating the kinetics and the products of the reactions of the two compounds with Cl atoms, OH radicals, OD radicals, and O3. FTIR smog chamber experiments measured: k(Cl + Z-CF3CH[double bond, length as m-dash]CHCF3) = (2.59 ± 0.47) × 10-11, k(Cl + E-CF3CH[double bond, length as m-dash]CHCF3) = (1.36 ± 0.27) × 10-11, k(OH + Z-CF3CH[double bond, length as m-dash]CHCF3) = (4.21 ± 0.62) × 10-13, k(OH + E-CF3CH[double bond, length as m-dash]CHCF3) = (1.72 ± 0.42) × 10-13, k(OD + Z-CF3CH[double bond, length as m-dash]CHCF3) = (6.94 ± 1.25) × 10-13, k(OD + E-CF3CH[double bond, length as m-dash]CHCF3) = (5.61 ± 0.98) × 10-13, k(O3 + Z-CF3CH[double bond, length as m-dash]CHCF3) = (6.25 ± 0.70) × 10-22, and k(O3 + E-CF3CH[double bond, length as m-dash]CHCF3) = (4.14 ± 0.42) × 10-22 cm3 molecule-1 s-1 in 700 Torr of air/N2/O2 diluents at 296 ± 2 K. E-CF3CH[double bond, length as m-dash]CHCF3 reacts with Cl atoms to give CF3CHClC(O)CF3 in a yield indistinguishable from 100%. Z-CF3CH[double bond, length as m-dash]CHCF3 reacts with Cl atoms to give (95 ± 10)% CF3CHClC(O)CF3 and (7 ± 1)% E-CF3CH[double bond, length as m-dash]CHCF3. CF3CHClC(O)CF3 reacts with Cl atoms to give the secondary product CF3C(O)Cl in a yield indistinguishable from 100%, with the observed co-products C(O)F2 and CF3O3CF3. The main atmospheric fate for Z- and E-CF3CH[double bond, length as m-dash]CHCF3 is reaction with OH radicals. The atmospheric lifetimes of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 are estimated as 27 and 67 days, respectively. IR absorption cross sections are reported and the global warming potentials (GWPs) of Z- and E-CF3CH[double bond, length as m-dash]CHCF3 for the 100 year time horizon are calculated to be GWP100 = 2 and 7, respectively. This study provides a comprehensive description of the atmospheric fate and impact of Z- and E-CF3CH[double bond, length as m-dash]CHCF3.