The Carbon Footprint of Single-Use Flexible Cystoscopes Compared with Reusable Cystoscopes

Abstract

Introduction:

Single-use devices for endourologic procedures are becoming more popular. The environmental impact of single-use instruments is relatively unknown. This study aimed to compare the carbon footprint of single-use vs reusable flexible cystoscopes based on waste production and estimated carbon emissions.

Methods:

An analysis of the solid waste produced when using the aScope™ 4 Cysto (Ambu^®) single-use flexible cystoscope compared with the reusable Cysto-Nephro Videoscope CYF-VA2 (Olympus^®) was performed. The solid waste generated was measured (grams) and recorded as either recyclable, landfill, or contaminated, and carbon dioxide (CO₂) produced by disposal, manufacture, and cleaning was calculated.

Results:

A total of 40 flexible cystoscopies (20 single-use and 20 reusable) were analyzed. Median total weight of waste produced was 622 g (interquartile range [IQR] 621–651) for the single-use cystoscope compared with 671.5 g (IQR 659–677.5) for the reusable cystoscope (p < 0.0001). More waste was disposed of by incineration after single-use than reusable cystoscopy (496 g [IQR 495–525] vs 415 g [IQR 403–421.5], p < 0.0001). However, more waste went to landfill after reusable cystoscopy (256 g ± 0 vs 126 g ± 0, p < 0.0001). There was no difference in weight of waste produced based on the indication for cystoscopy (p = 0.1570). A total of 2.41 kg of CO₂ (IQR 2.40–2.44) was produced per case for the single-use flexible cystoscope compared with 4.23 kg of CO₂ (IQR 4.22–4.24) for the reusable cystoscope (p < 0.0001).

Conclusion:

Environmental accountability is essential in modern health care. This study highlights that disposable flexible cystoscopes have a significantly lower impact on the environment in terms of carbon footprint and landfill. We propose that environmental impact studies should be a routine part of device development for a sustainable future.

Introduction

Endourologic surgery has advanced considerably since the first reported observation of the urethra in 1878.¹ Initially, cystoscopy was limited to observation through a lens in either side or forward view. The introduction of the first flexible cystoscope in 1973 allowed for improved observation of the bladder neck.² These instruments have all been reusable, undergoing sterilization between uses.³ In recent years, there has been a move not just in endourology but also in general surgery and bronchoscopy, among others, toward single-use disposable instruments.^4

–8 These devices are marketed with the advantage of fewer resources required per patient.⁹ A recent study assessing urologists willingness to convert to single-use devices demonstrated that 44.5% would consider changing to single use.¹⁰

Climate change is a significant threat to society, with greenhouse gas emissions identified as the driving force. Globally, health care is estimated to contribute 4% to 5% of overall greenhouse gas emissions, with medical equipment a significant component.¹¹ It has been suggested that with increasing overdiagnosis of low-risk diseases, there is a correlation with an unnecessary increase in the carbon footprint for health care.¹² Single-use instruments are being increasingly used in urology, and the environmental impact of these devices is unknown. It is the goal of this study to assess the environmental impact of disposable flexible cystoscopes.

Methods

This analysis was a prospective single-center cohort study. The inclusion criteria were all flexible cystoscopies performed at our institution between August and September 2021. Patients who had concurrent procedures such as stent removal were excluded to avoid confounding factors. The proposed number of patients in the study groups was determined by a priori power analysis with G Power 3.1.9.4. A target sample size of >36 patients was determined as a minimum recruitment number needed by accepting α risk of 5% (0.05) and a β risk of 10% (0.9) in a two-sided test. The study therefore aimed to enroll 40 cystoscopies (20 single-use and 20 reusable).

The reusable cystoscope used at our institution is the Olympus^® SD Flexible Cysto-Nephro videoscope (CYF-VA2). These are sterilized between each use, starting with a preclean immediately after cystoscopy, followed by sterilization in an EndoThermo Disinfectors (ETD) endoscopic reprocessing machine. They are then repacked in a vacuum-sealed plastic container to allow storage for 72 hours. The average lifespan of these instruments is 7 years. Each year roughly 2000 flexible cystoscopies are performed in our department spread between 12 cystoscopes, ∼160 cystoscopies per year per cystoscope. The environmental impact of this device was compared with that of the single-use Ambu^® aScope™ 4 Cysto. These are packaged into their pouch, inner box, and outer box and sterilized in bulk using ethylene oxide (EtO) according to EN ISO 11135 and EN 556-1.¹³

The carbon dioxide (CO₂) emissions relevant to cystoscopy include device manufacture, transport, sterilization, landfill, and incineration. The method of disposal was determined by the hospital policy for health care waste being either “household” or “contaminated.” The total CO₂ produced when sterilizing endoscopic devices by EtO has previously been calculated as 0.3 kg of CO₂.⁵ An environmental impact review has previously reported that EtO release to the atmosphere is unlikely to have a significant effect.¹⁴

Weights were recorded using a digital scale in grams (g). Before starting the case, device packaging items disposed of in a household waste bin were weighed separately to items used in contact with the patient disposed of in a clinical waste bin. Individual items were weighed just once to obtain their weight. The solid waste generated (g) during each case was calculated and converted into the equivalent mass of carbon dioxide (kg of CO₂) released based on its mode of disposal.¹⁵ To assess CO₂/kg of raw material produced by the equipment, a standardized CO₂ protocol was followed.^16

–19 This was 6 kg of CO₂ per kg of plastic, 1.16 kg of CO₂ per kg of rubber, 1.8 kg of CO₂ per kg of steel, and 150 kg of CO₂ per kg of electronics. Detailed data were obtained from the Ambu research and development team outlining the flexible cystoscope comprising plastic (92.6%), steel (4%), electronics (1.8%), and rubber (1.6%). We then calculated the manufacturing cost of a flexible cystoscope as 8.51 kg of CO₂ per 1 kg of cystoscope.⁵

A calculation was performed based on one imperial tonne (1016 kg) of waste incinerated, producing 1246 kg of CO₂, meaning that each 1 kg of waste incinerated produces 1.23 kg of CO₂.²⁰ According to the United States Environmental Protection Agency, 132 million metric tonnes of waste goes to landfills annually in the United States, producing 114.5 million metric tonnes of CO₂ equivalent, meaning every 1 kg of solid waste disposed of at landfill produced 0.85 kg of CO₂.²¹

The carbon footprint of transport of single-use flexible cystoscopes was calculated based on an average of 26.5 g of CO₂ produced per tonne-kilometer in dry freight over the 10,791 km distance from the manufacturing factory in Penang, Malaysia to Cork, Ireland.²² This amounts to 285.96 kg of CO₂ per tonne per journey, and each 170 g cystoscope (including packaging) producing 0.049 kg of CO₂.

Data analysis was performed using Stata Statistical Software: Release 17 (STATACorp, LLC, College Station, TX). A Shapiro–Wilk test was used to test for normality. All data were non-normally distributed, therefore a Mann–Whitney U test was used to compare median values. A two-sided p-value <0.05 was considered statistically significant.

Results

This study recorded waste produced during 40 flexible cystoscopies (20 single-use and 20 reusable). There were 20 cystoscopies performed on male patients and 20 on female patients. Overall, 22 cystoscopies were performed for diagnostic purposes and 18 for bladder tumor surveillance.

Solid waste produced

The median total weight of waste produced was 622 g (interquartile range [IQR] 621–651) for the single-use cystoscope compared with 671.5 g (IQR 659–677.5) for the reusable cystoscope (p < 0.0001). The single-use cystoscope alone accounted for 25.4% of the total waste and 27.3% when outer packaging was included. There was a higher proportion of waste disposed of by incineration after single-use cystoscopy with a median of 496 g (IQR 495–525) vs 415 g (IQR 403–421.5) after reusable cystoscopy (p < 0.0001).

However, more waste went to landfills after reusable cystoscopy with a mean of 256 g ± 0 vs 126 g ± 0 after single-use cystoscopy (p < 0.0001). In general, it appeared that less waste was produced after a male cystoscopy with 622.5 g (IQR 621–658.5) vs 671.5 g (IQR 653.5–677.5) for a female cystoscopy (p < 0.0001). We hypothesize this may be because of the use of less Instillagel™ for a female cystoscopy, leaving more in the syringe that was weighed after the procedure. There was no difference in the total weight of waste produced based on the indication (p = 0.1570). No waste was recycled. A comparison of waste produced is illustrated in Figure 1.

FIG. 1.

Comparison of waste produced.

Carbon footprint of waste products

The single-use cystoscope weighs 158 g in total (146.31 g plastic, 6.32 g steel, 2.84 g electronics, and 2.53 g of rubber), giving a manufacturing carbon footprint of 1.34 kg of CO₂ per cystoscope. The solid waste disposed of by incineration after single-use flexible cystoscopy produced a median of 0.61 kg of CO₂ (IQR 0.50–0.64) and waste to landfill producing 0.11 kg of CO₂ (IQR 0) per case. Sterilization of single-use endoscopes produces 0.3 kg of CO₂ (IQR 0) per endoscope.⁵ Transport of each single-use cystoscope from the manufacturing factory in Malaysia produced 0.049 kg of CO₂ as described in the Methods section. The total median carbon footprint was 2.41 kg CO₂ (IQR 2.40–2.44) per case for the single-use flexible cystoscope.

The manufacturing production of CO₂ of a reusable cystoscope was similarly calculated based on a weight of 1.3 kg for the Olympus cystoscope giving 14.94 kg of CO₂ per cystoscope. However, given these perform roughly 1120 cystoscopies in a lifetime, this amounts to just 0.013 kg of CO₂ (IQR 0) per case. The solid waste disposed of by incineration after reusable flexible cystoscopy produced a median of 0.52 kg of CO₂ (IQR 0.51–0.60) and waste to landfill produced 0.22 kg of CO₂ (IQR 0) per case. Sterilization performed within the department using the Olympus ETD-Double™ can reprocess up to three cystoscopes per cycle, with a cycle consuming 10.5 kW of electricity, equating to 10.5 kg of CO₂ per cycle or 3.5 kg of CO₂ (IQR 0) per case.²³ The total median carbon footprint was significantly higher at 4.23 kg of CO₂ (IQR 4.22–4.24) per case for the reusable flexible cystoscope (p < 0.0001). A summary of CO₂ emissions per case is outlined in Table 1.

Table 1.

Comparison of Carbon Dioxide Emissions Per Cystoscopy Case

	Single-use flexible cystoscope (kg CO₂)	Reusable flexible cystoscope (kg CO₂)	p
Incineration	0.61 (0.50–0.64)	0.52 (0.51–0.60)	0.3230
Landfill	0.11 (0)	0.22 (0)	<0.0001
Sterilization	0.3 (0)	3.5 (0)	<0.0001
Manufacture	1.34 (0)	0.013 (0)	<0.0001
Transport	0.049 (0)	N/A	—
Total	2.41 (2.40–2.44)	4.23 (4.22–4.24)	<0.0001

Statistically significant results are highlighted in bold.

Data expressed as median (interquartile range).

CO₂ = carbon dioxide; N/A = not applicable.

Discussion

Flexible cystoscopy is a common urologic procedure. Annually more than 20,000 cystoscopies are performed in Ireland alone.²⁴ To facilitate flexible cystoscopy at an institution, significant capital investment is required not only in relation to the cystoscope itself, but also the audiovisual stack and the sterilizing equipment, as well as storage space for these large items.²³ With recent technological advancements single-use flexible cystoscopes have been adopted as an alternative, avoiding the need for a significant investment, and instead purchasing a device per case. Although this has a significant financial benefit for institutions, there remains uncertainty surrounding the environmental impact of these devices.⁹

Surprisingly, this study demonstrates a significantly higher carbon footprint produced by the reusable cystoscope compared with the single-use device. Although the manufacturing element of the process is significantly lower in terms of CO₂ production per case, this is swiftly shadowed by the carbon cost in terms of sterilization as well as solid waste being sent to landfills. Sterilization is a time-consuming process that involves much more than packing the device into a cleaner, with steps including dismantling, precleaning, leak-testing, cleaning, rinsing, drying, sterilization, packing, and storage. All of this requires significant staffing and equipment, as well as water usage of up to 165 L per cleaning cycle.⁵

EtO sterilization produces toxic gases that are carcinogenic to humans when inhaled, increasing the risk of lymphoma and breast cancer, although EtO in commercial premises is generally captured in a scrubber and combined with water and sulfuric acid to create ethylene glycol, which is then repurposed for commercial use.^25,26 This also produces significant detergent wastes; however, as a previous study has mentioned, this is generally captured and treated before re-entering the municipal water system.²⁷

Solid waste produced by flexible cystoscopy will vary according to local institutional guidelines. In our department, a large amount of waste sent to landfills is because of the repackaging practice. This was caused by the reusable cystoscope being packaged in a vacuum-packed semihard single-use plastic sleeve after reprocessing. Although this caused landfill waste, it accounted for just a small amount of the total CO₂ produced for the reusable cystoscope; therefore, our results may still be extrapolated to other centers. In contrast to reports already in the literature reviewing the carbon footprint of flexible ureteroscopes, this study identified a significantly lower carbon footprint for single-use flexible cystoscopes than flexible ureteroscopes.⁵ This is likely mainly caused by the decreased weight of the disposable cystoscope compared with the disposable ureteroscope, which translates to decreased carbon footprint in manufacturing for disposable cystoscopes.

Research into carbon emissions and the environmental impact of single-use devices in health care is growing. Recently, Hii et al. identified issues with supply and demand relating to single-use items in the pandemic era.²⁸ When there are supply chain issues with items such as ventilators and personal protective equipment, as well as the international shortage of microchips, there must be a balance between avoiding CO₂ production from reprocessing vs avoiding reliance on shipping.^28,29 This needs to be kept in mind where, although reprocessing consumes large quantities of energy and water, the raw materials are not lost as they are with single-use cystoscopes. As a tried alternative to avoid deep decontamination between flexible cystoscopy cases, endosheaths were introduced. However, the use of these resulted in poor vision and occasional patient discomfort.³⁰

The authors acknowledge there are limitations to this study. First, the data are limited to a single center and may not be similar to the waste produced by other centers for the same procedure owing to items available. In line with this, the brand of cystoscope and, therefore, the method of sterilization may differ between centers and, therefore, this cannot be extrapolated to centers using different equipment. Second, the data we based our carbon footprint outcomes on are from online sources, although this is similar to other studies reviewed in this field. Where possible, government and environmental agency data were used to support the results of this study. It was not possible to obtain detailed calculations on EtO sterilization; therefore, this calculation is based on information from a previous study.⁵

Not included in this study was the carbon footprint for repairs and maintenance for the reusable cystoscope. Given that the carbon footprint was already significantly higher for the reusable cystoscope, adding this would only further increase the carbon footprint and would not significantly alter the outcome of the study. This study reviews the carbon footprint solely and does not address the overall environmental impact, which includes full life cycle analysis assessment of impacts (“flows”) to and from nature, before, during, and after product use. We, therefore, have not reported on the volume of toxic waste produced in relation to the cystoscopes themselves or any harmful gases produced during sterilization processes.

Conclusion

Globally, health care contributes significantly to overall greenhouse gas emissions, and it will become increasingly more important to determine the environmental impact of new technologies. In this study, we demonstrated that compared with reusable flexible cystoscopy, the carbon footprint of single-use devices was significantly lower.

Footnotes

Authors' Contributions

D.B.H. and D.H. were involved in study conception, design, and planning. D.H. and H.R. were involved in data collection. D.H., D.B.H., and N.K. were involved in data analysis and writing of the article. All authors have reviewed and approved the final draft of the article before submission.

Disclaimer

We confirm that this article has not been published or submitted for publication elsewhere and that all authors have contributed significantly and are all in agreement with the content of the article.

Author Disclosure Statement

All authors confirm that they have no conflicts of interest to disclose.

Funding Information

Not applicable.

Abbreviations Used

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