Introduction
Previous infection outbreaks linked to contaminated duodenoscopes have led to the development of novel and fully disposable single-use duodenoscopes (SUDs) to avoid cross-contamination risk [1]. Over the period from 2008 to 2018, 490 cases of contamination of reusable duodenoscopes (RUDs) were reported worldwide, resulting in 32 patient fatalities, which is an extremely low mortality rate [2]. Most outbreaks were attributed to nonadherence to cleaning protocols, with a notable decline in reported infections after enhanced cleaning and reprocessing techniques were mandated by the U.S. Food and Drug Administration (FDA), dropping from a peak of 250 cases in 2015 to 36 cases in 2018 [3].
SUDs have no theoretical risk of infection and no reprocessing costs; however, the wider environmental health effects of SUD use for endoscopic retrograde cholangiopancreatography (ERCP) have not been analyzed to support their global implementation. Recent environmental assessments have shown that healthcare systems account for 4.4%–5.4% of the total carbon footprint and that gastrointestinal (GI) endoscopy units are the third largest producer of biomedical waste in a hospital setting [4]
[5]
[6]. It has been suggested that, on average, each endoscopy procedure generates up to 2.1 kg of general waste [7] and approximately 28.4 kg of carbon dioxide equivalents (kg CO2eq) [8]. In addition, sustainability measures to separate and recycle waste can result in a 31.6% reduction in total carbon emissions [9].
A recent estimate has suggested that SUDs are 24–47 times more polluting than RUDs in terms of kg CO2eq [10]. The material composition of recently developed SUDs has however not been analyzed, so exact differences in carbon footprint between SUDs and RUDs have not yet been evaluated. In line with European regulations, these SUDs fall under the category of biomedical waste, necessitating their incineration. This process significantly amplifies pollutant emissions compared with disposal in landfill sites. Material composition analysis is a crucial step in assessing carbon emissions. Recent findings on the material composition and environmental impact of single-use endoscopy devices revealed significant differences between manufacturers [11].
We aimed to accurately determine the material composition of RUDs and SUDs and compare the carbon footprint between reusable and single-use sustainability strategies in order to understand the environmental impact of our daily practice if SUDs were to be partially or globally adopted.
Methods
Study design
This study was a single-center descriptive study conducted at La Fe University Hospital in Valencia, Spain. It was purely descriptive in order to compare various scenarios by highlighting the novelty and improvement achieved by identifying accurately the material composition of the different endoscope components. It was designed to evaluate the material composition and carbon footprint of one RUD and two SUDs from different manufacturers (A & B). In addition, the environmental impact of routine ERCP practice was assessed in three sustainability strategies: (i) an exclusively reusable scenario, (ii) an exclusively single-use scenario, and (iii) a reusable scenario with occasional use of SUDs. We assumed a standard performance of five ERCPs per week and an RUD lifetime of 8 years, resulting in 1600 procedures. We compared the environmental impact of 1600 uses of an RUD (production, transportation, and reprocessing) with that of 1600 ERCP procedures using SUDs (production, transportation, waste management), and a combination of 1405 uses of an RUD plus 195 procedures using SUDs.
In our third sustainability scenario, we considered the use of SUDs when patients are colonized with multidrug-resistant organisms (MDROs) and when the ERCP is urgent and cannot be delayed more than 24 hours (8.2%; 132 patients) [12]. The remaining patients without septic shock could wait 3–5 days for culture results (1468 patients). Taking into account a 4.3% rate of MDRO colonization [13], 63 of these patients would test positive and undergo ERCP with SUDs.
Material composition analysis was performed at the Centre for Biomaterials and Tissue Engineering of the Universitat Politècnica de València. The study team was blinded to the endoscope brand.
The duodenoscopes were analyzed using energy dispersive X-ray (EDX) analysis and field emission scanning electron microscopy (FESEM) for metal parts and differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy for the polymeric parts [14].
The first stage in LCA, according to ISO 14040, is the definition of the objective and scope [15]. In this case, the main objective was to assess the carbon footprint associated with RUDs and SUDs in three different scenarios in order to conduct a realistic and detailed comparison of the environmental impact, in terms of global warming potential. This comparison was designed to provide information of the carbon footprint (kg CO2eq) for each stage of the life cycle of the duodenoscopes under study, in a cradle-to-grave LCA model (manufacturing, transportation, incineration/reprocessing). In this way, it is possible to determine which of them represents the most sustainable option and to offer improvements in material composition to reduce this impact.
[Fig. 1]shows an overview of the LCA system boundary, with the included and non-included information for our analysis.
Fig. 1 Life cycle assessment system boundary for our analysis of duodenoscopes.
A meticulous laboratory analysis provided precise insights into the weight and composition of duodenoscopes, aiding in determining the material components employed by manufacturers in production. This facilitated the calculation of greenhouse gas emissions associated with production and transportation of the SUDs and RUD, allowing us to identify the most sustainable device. The detailed life cycle inventory of material production and transportation, as well as the assumptions associated with waste treatment, are summarized in Table 1s, see online-only Supplementary material.
Several assumptions were made to estimate the carbon emissions from transport. Continental routes taken by a diesel lorry were estimated from the manufacturing site to the nearest international port. Transoceanic routes were estimated by considering the distance between this international port and the port of Valencia, Spain. Emissions from transportation between the port of Valencia and our hospital were not evaluated. Therefore, the shortest international transport route was assumed to be 18 000 km by cargo ship (SUD-A), 8000 km by cargo ship plus 800 km by diesel lorry (SUD-B), and 14 000 km by cargo ship (RUD). It is important to note that manufacturing and assembly steps (injection, extrusion, and lamination), constituting approximately 15% of the total environmental impact, were not included in the calculations owing to limitations in the available databases [16].
The environmental costs of reprocessing and disinfecting the RUD were included in the global LCA. Our estimation per reprocessing cycle was 91 L of clean water, 0.33 kWh of energy needs, and solvents and detergents [7]. We evaluated the environmental impact of disinfection chemicals for automated reprocessing with the EndoThermo washer-disinfector (ETD; Olympus, Hamburg, Germany), which are approximately 0.12 g of ethoxylated fatty alcohols, 0.12 g of sodium cumenesulphonate, 0.5 g of acetic acid, 0.5 g of 100% hydroxide peroxide, and 1 g sodium hydroxide [17]. Water and electricity consumption were calculated using greenhouse gas conversion factors: emissions for electricity (0.19 kg CO2eq/kWh) and water consumption (0.15 kg CO2eq/m3) [18].
As with all biomedical waste, incorporating SUDs requires their disposal by high temperature incineration. End-of-life emissions were approximated on the basis of the most recent waste stream information available in the literature [9]
[19]
[20]. The incineration of general biomedical waste was estimated to be 1.1 kg CO2eq/kg for nonplastics [20]. As SUDs are hazardous waste for incineration, mainly composed of plastics, estimations vary between 3 and 6 kg CO2eq/kg for plastics [9]
[21] and we assumed a worst-case environmental scenario.
We did not consider other sources of greenhouse gas emissions, such as electricity consumption during ERCP, medical and non-medical equipment, other consumables, general waste, or travel. Our analysis was limited to production, transportation, end-of life, and reprocessing of duodenoscopes.
The environmental footprint was estimated using a free LCA software package (openLCA V.2.0.3; GreenDelta GmbH, Germany). This software assesses the effects that a product has on the environment over its entire life cycle. The LCA databases used for the life cycle inventory analysis were EF Secondary Data sets V. EF 2.0 and attributional analysis was chosen, focused on quantifying the different environmental impacts without considering broader systemic effects, unlike consequential analysis. The impact assessment method used was EF (midpoint indicator).
The environmental assessment of the manufacturing process covered a range of other environmental indicators, such as acidification potential, water use, resource use (minerals and metals), and ionizing radiation. The results are presented in terms of moles of hydrogen ion equivalents (mol H+eq), m3, kg of antimony equivalent (kg Sb-eq), and kg of 235uranium equivalent (kg 235U-eq), respectively.
Outcomes
The primary outcome was to determine the material composition and carbon footprint of the RUD and two SUDs. Our secondary outcome was to assess the environmental impact by comparing three sustainability strategies over the lifetime of a duodenoscope: (i) the conventional strategy using RUDs, (ii) the global implementation of SUDs in clinical practice, and (iii) a scenario consisting of a combination of 1405 uses of an RUD plus 195 procedures using SUDs.
Results
Material composition
The RUD was more than three times heavier than SUD-A and SUD-B: 3489 g, 943 g, and 716 g, respectively. Thermochemical analysis using FTIR, EDX, DSC, and TGA was performed to estimate the most likely material composition ([Table 1]). The main components of the RUD were metal alloys (95%), such as brass, nickel and aluminum alloys, and stainless steel. In contrast, SUD-A and SUD-B were mainly made of plastic polymers and resins (70% and 81%, respectively), and the composition was remarkably different between them, with polyethylene derivatives, acrylonitrile butadiene styrene, and polyester urethane in the case of SUD-A, and polycarbonates and polytetrafluoroethylene in the case of SUD-B. SUDs were made of plastics that have a critical global warming potential, in particular one of the main components of SUD-A (acrylonitrile butadiene styrene) and SUD-B (polycarbonate) ([Fig. 2]). In contrast, the RUD consists mainly of metal components, with a high recycling potential, thereby reducing the global warming potential contribution. The proportion of high or low global warming potential materials are shown in Fig. 1s.
Fig. 2 Material composition and weight of the analyzed duodenoscopes. Al, aluminum; Ni, nickel; Cu, copper; PDMS, polydimethylsiloxane; PTFE, polytetrafluoroethylene; SS, stainless steel; ABS, acrylonitrile butadiene styrene; LDPE, low-density polyethylene; PC, polycarbonate; PET, polyethylene terephthalate; PEU, polyurethane polyester; TPU, thermoplastic polyurethane.
Table 1 Material composition and weight of the analyzed single-use and reusable duodenoscopes (without packaging).
|
|
Reusable
|
Single use A
|
Single use B
|
|
Composition, %
|
|
|
–
|
34.0
|
15.5
|
|
|
–
|
23.8
|
42.0
|
|
|
4.9
|
0.1
|
8.1
|
|
|
–
|
11.6
|
16.3
|
|
|
95.1
|
30.5
|
18.2
|
|
Total weight, g
|
3489
|
943
|
716
|
Environmental footprint
There were environmental differences between SUD-A and SUD-B (7.9 and 6.6 kg CO2eq per endoscope, respectively). This difference between the two brands amounted to 2128 kg CO2eq over the lifetime of an RUD.
The RUD manufacturing process produced far more emissions than those of SUD-A and SUD-B (22.8 vs. 3.7 and 3.2 kg CO2eq, respectively). This is because the RUD was much heavier than the SUDs and consisted mainly of metal components, which are more polluting to produce, but are more environmentally friendly at their end-of-life, as they can be easily recycled. For the two SUDs, which consisted mainly of plastics (high global warming potential waste), incineration was the main source of emissions ([Fig. 3]).
Fig. 3 Carbon emissions generated by production, transportation, incineration, and reprocessing per ERCP, assuming a reusable duodenoscope is reprocessed 1600 times.
In terms of acidification, water and resource use, and ionizing radiation, the production of an RUD is more harmful to the environment than an SUD, as it is a more complex and heavier device. Acidification was twice as high for SUD-A compared with SUD-B and water consumption was considerably higher; however, we found no differences in ionizing radiation and resource use ([Table 2]).
Table 2 Environmental impact of production of the duodenoscopes in relation to other environmental indicators.
|
|
Reusable
|
Single use A
|
Single use B
|
|
mol H+eq, moles of hydrogen ion equivalents; kg Sb-eq, kilograms of antimony equivalent; kg 235U-eq, kilograms of 235uranium equivalent.
|
|
Acidification, mol H+eq
|
0.16
|
0.02
|
0.011
|
|
Water use, m3
|
7.17
|
1.31
|
0.91
|
|
Resource use, kg Sb-eq
|
0.00116
|
0.00012
|
0.00012
|
|
Ionizing radiation, kg 235U-eq
|
0.95
|
0.15
|
0.15
|
The three environmental scenarios of the RUD and SUDs, assessed by LCA over the lifetime of a RUD, are shown in [Fig. 4].
Fig. 4 Total carbon emissions from production, transportation, incineration, and reprocessing of single-use and reusable duodenoscopes over the lifetime of a reusable duodenoscope (approximately 8 years).
The carbon footprint of all duodenoscopes sorted by production, transportation, reprocessing, and incineration is shown in Table 2s. The carbon footprint for the lifespan of a reusable duodenoscope amounted to 152 kg CO2eq ([Fig. 4]), with reprocessing and disinfection of 1600 cleaning cycles accounting for 84% of the total emissions (0.08 kg CO2eq per cleaning cycle). This reusable strategy was 82–62 times more sustainable over the lifetime of the RUD than global implementation of SUDs (12640–10512 kg CO2eq), which in terms of greenhouse gas emissions is equivalent to heating an apartment for 3 years [22]. The reusable approach with occasional use of SUDs accounted for 1677 kg CO2eq in the case of SUD-A and 1417 kg CO2eq in the case of SUD-B, being approximately 10 times more harmful to the environment than the exclusively reusable strategy.
Discussion
Understanding the exact material composition and the environmental impact of SUDs and RUDs is essential for selecting the most sustainable strategy. The novelty of this work entailed a much more accurate approach to identify and compare the carbon emissions of different brands of RUDs and SUDs.
Material composition analysis revealed differences between the RUD and SUDs. The main components of the RUD were metal alloys (95%), while SUDs were mainly made of polymers, such as acrylonitrile butadiene styrene and polyester urethane in the case of SUD-A (70%), and polycarbonate and polytetrafluoroethylene in the case of SUD-B (81%). From LCA, we found that the most sustainable polymers for production were polyethylene terephthalate, high density and low density polyethylene, and polypropylene (0.7–2.3 kg CO2eq/kg of production) and the most sustainable metal was brass (2.1 kg CO2eq/kg of production). Polymers with higher environmental impacts were thermoplastic polyester urethane (5.3 kg CO2eq/kg) and polytetrafluoroethylene (12.8 kg CO2eq/kg) due to their fluoridated chemical components. The more suitable metal elements were the ones with higher proportions of aluminum and nickel alloys (11.8 and 12.8 kg CO2eq/kg, respectively). These data highlight how fundamental it is for manufacturing companies to report the exact material composition of their products to precisely quantify the environmental impact of certain materials to ensure that potential buyers select the most environmentally suitable choice.
Comparative analysis of global warming potential showed 5% high global warming potential materials for the RUD, compared with 70% and 81% for SUD-A and SUD-B, which contributes significantly to the release of greenhouse gases that are harmful to the environment. Metals tend to have a lower overall global warming potential compared with certain plastics because the greenhouse gas emissions are usually outweighed by the benefits of metal recycling [23].
There are large differences in the carbon footprints per duodenoscope use between the RUD and SUDs, and relevant differences between the different SUDs manufacturers: RUD (23.8 kg CO2eq) vs. SUD-A (7.9 kg CO2eq) vs. SUD-B (6.6 kg CO2eq). The other environmental indicators also showed that SUD-A was more harmful in terms of acidification and water use than SUD-B. These comprehensive findings provide a holistic view of the environmental performance, allowing for a more informed decision-making process in terms of sustainability and resource management. We acknowledge that readers would strongly prefer us to include the names of the companies; however, there is no legislation in place to force manufacturing companies to provide information on material composition. Our aim in this area is to encourage companies to change the design of their endoscopes and provide us with a detailed composition and the sources of the materials they use.
The FDA's 2022 Safety Communication recommends transitioning from older model duodenoscopes (4%–6% high concern organism contamination) to novel designs that facilitate cleaning with disposable endcaps (0% rate of reprocessing failure and only 1.1% tested positive for high concern organisms) [24]. Owing to their single-use nature, SUDs have been reported to potentially eliminate all duodenoscope-associated infections (i.e. exogenous infections caused by microorganisms outside the patient’s body); however, one may question the ability of SUDs to prevent endogenous infections caused by translocation of microorganisms from the patient’s own intestinal flora, a risk inherent to any endoscopic procedure.
The largest cohort studying ERCP-related adverse events with SUDs showed an overall infection rate of 1.6% [25], which is similar to the classic analysis by Andriulli et al., which included 16 855 patients (1.4%) [26]. The comparable infection rate also shows that endogenous infection can still occur with the use of an SUD, so the procedure-related infection rate is not guaranteed to be lower than the rate for RUDs [25].
Despite these data, SUDs may prove economically advantageous in intensive care units or operating rooms, owing to the potential likelihood of hospitalized patients being colonized with MDRO, and in low-volume facilities unwilling to invest in reprocessing equipment [27]. Therefore, SUDs may have a role in such cases and in emergency ERCP. Rather than the universal use of SUDs, if we consider occasional use in emergency situations and in procedures on MDRO-colonized patients, the environmental impact is reduced almost tenfold.
The universal use of SUDs produces 62–82 times more carbon emissions than RUDs, and over the approximate lifetime of just one RUD, the global adoption of SUDs would be equivalent to producing 220 000 plastic bottles of water. Reprocessing is often cited as a major contributor to the economic costs and environmental footprint of reusable endoscopes and is often used to justify single-use strategies [28]
[29]; however, the present study reveals that reprocessing accounts for only a small portion of the carbon footprint (128 kg CO2eq) over the lifetime of an RUD, compared with the contribution of end-of-life incineration for the same number of procedures with SUDs (6176–5152 kg CO2eq).
Travel has been shown to have the largest environmental impact in outpatient endoscopy [8]. The LEAFGREEN survey on green practices in GI endoscopy showed that most healthcare professionals live within a 20-km radius of their workplace [30]. If disinfection and reprocessing of RUDs were to require the presence of an additional technician, 2400 kg CO2eq should be added, assuming a daily round trip of 40 km by car for 1 year. In low-volume ERCP hospitals (<40 cases per year), the reusable strategy results in 27 kg CO2eq over 1 year (production and transport of one RUD, plus 40 reprocessing cycles). In contrast, using SUD-B, the production, transport, and incineration of 40 SUDs accounts for 263 kg CO2eq. Although most endoscopy units already employ one or two technicians to reprocess endoscopes, the single-use scenario would be more sustainable if an additional technician were required.
The European Society of Gastrointestinal Endoscopy's (ESGE) Green Endoscopy Working Group has proposed several strategies to improve sustainability without compromising patient care, emphasizing the strict use of SUDs for selected indications [31]. In previous estimations, waste management only accounted for 3% of the global carbon footprint [8]. In our study, the ERCP disposable strategy for SUDs would generate 4.7 kg of biomedical waste per week. The fact that almost 5 kg of plastic would have to be incinerated every week is a major environmental concern [32]
[33].
There is scarce evidence in the literature on the environmental impact of SUDs. Le et al. [10] reported that, primarily owing to manufacturing, SUDs generate higher greenhouse gas emissions (ranging from 36.3–71.5 kg CO2eq per ERCP) than RUDs (1.5 kg CO2eq), based on the composition of a reusable ureteroscope (90% plastic, 4% steel, 4% electronics, and 2% rubber). However, our analysis indicated that SUDs contain 30% metals in the case of SUD-A and 18% in the case of SUD-B. Furthermore, Le et al. assumed polyvinyl chloride to be the predominant component (90%) of SUDs, whereas this polymer was not found in either of the SUDs in our analysis. The substantial disparities between these environmental findings may stem from differences in material composition or the exclusion of emissions from assembly or injection molding stages in the manufacturing process, an assumption we made under the premise of the similarity between RUDs and SUDs. These facts highlight the importance of material composition analysis to standardize the overall LCA. In addition, we estimated that the environmental impact of incinerating SUDs was substantial and almost equal to the emissions from the manufacturing process.
Our study identified certain limitations in quantifying the environmental impacts: (i) the assessment of end-of-life emissions was estimated from literature references [9]
[19]
[20] owing to the inability to access LCA software databases containing data on emissions from high temperature incineration of biomedical waste, where both open-access and professional software are comparable tools for assessing carbon emissions related to GI endoscopy practice, with urgent need of a universal database to mitigate disparities in data access and enable standardized calculations [34]; (ii) we did not include emissions associated with the transport of raw materials from their extraction sites to the manufacturing facilities, or the transport of biomedical waste from healthcare facilities to incinerators; (iii) the assembly stages of production were not calculated in the analysis, so the manufacturing process could slightly increase carbon footprint values [35], resulting in 0.07 kg CO2eq [8].
The findings of this study highlight the importance of “green-preferable purchasing,” a business strategy that refers to a procurement process where organizations prioritize environmentally friendly products and services over those with negative environmental impacts. We propose that all endoscopy supplies and instruments should carry an environmental label indicating their material composition, together with a comprehensive analysis of their life cycle and carbon footprints [36]
[37].
In conclusion, our study highlights the fact that knowledge of material composition of endoscopy equipment is key to selecting the most sustainable alternatives. Our findings indicate that the widespread adoption of single-use endoscopes would have a considerably greater negative environmental impact, at least in high-volume ERCP centers. Therefore, to effectively minimize duodenoscope-related infection without compromising environmental health, we must focus on optimizing the disinfection processes associated with reusable endoscopes or explore innovative solutions involving the use of disposable components or partially recyclable endoscopes. In doing so, we can strike a balance between patient safety and environmental responsibility, ultimately contributing to more sustainable healthcare practices.
