Original research
Figure 1 Steps for conducting the life cycle impact assessment (LCIA). Step 1: dismantling Penthrox into its component parts and weighing these. The figure shows the Penthrox device along with a 3 mL vial of methoxyflurane in the top box. The methoxyflurane drug is represented by the tablet. Step 2: arrangement of each component part into flows with LCIA software. In the figure an example flow is shown. Step 3: data analysis.
hazardous waste bins and incinerated. All inputs and outputs for this flow are 19.4 g as that is the weight of this component. A full list of all flows with inputs and outputs are listed in online supplemental appendix 1. Step 3: results and data analysis as provided by the LCIA software. Functional unit The unit measure in this study was one unit of Penthrox with 3 mL of methoxyflurane 99.7%, equivalent to 30 min use. The UK product version assessed in this study includes a charcoal filter and alert card. Southampton General Hospital was used as The ‘system boundary’ considered in this project is summarised in figure 2. This includes the manufacture of all physical compo- nents and drugs through to assembly, transport, use and disposal of the product. All components were searched for on Ecoinvent V.3.8, an LCIA inventory database. 11 This is important for any LCIA project as the software running the analysis, in this proj- ect’s case, OpenLCA, draws on an LCIA inventory database for its data on previously logged LCIAs on various materials, prod- ucts and processes, which have used a standardised framework for their calculation. 12 Where a product or process is missing from Ecoinvent, an appropriate substitute can be used, or, as occurred in this project with the drug methoxyflurane, more analysis is required to fill this gap. Mechanism of drug synthesis the end destination. System boundaries Methoxyflurane had no matching record in Ecoinvent, therefore, potential reaction processes were searched for online. Three
The overall environmental impact can be calculated by carrying out a life cycle impact assessment (LCIA). The cradle- to-grave methodology of LCIAs calculates much more than the commonly measured ‘carbon footprint’, which only considers the carbon dioxide equivalent (CO 2 e). LCIA is a scientific method used to measure the entire environmental impact of a product or process, from raw material acquisition—the ‘cradle’—through its manufacture, transport and use, to product disposal—the ‘grave’. The primary aim of this project is to carry out an LCIA of the currently available formulation of methoxyflurane, Penthrox, also known as the green whistle. The secondary aim is to compare the climate change impact of Penthrox with that of N 2 O. METHODS We carried out an LCIA on Penthrox in July 2022. We have summarised the LCIA process into three steps (figure 1). Step 1: dismantling the Penthrox device into component parts and weighing each part. Each part was made of one material, and this was cross-referenced with data sent by the manufacturer. Step 2: entering data into LCIA software using ‘flows’. A flow consists of all inputs (raw materials, processes, transport and energy requirements) and outputs (waste disposal and excretion of drug) corresponding to each part of Penthrox. In figure 1 an example flow is shown. The flow is for the char- coal filter case which has the inputs of ‘polycarbonate’ as the raw material required for making the charcoal filter case and ‘injection moulding’ as the process required to make the char- coal filter case from the polycarbonate. The output of this flow is ‘hazardous waste incineration’ as at the end of the life cycle of Penthrox, it is assumed that the device will be thrown in the
Martindale AEV, et al . Emerg Med J 2024; 41 :69–75. doi:10.1136/emermed-2022-213042
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