Climate change has been classified as “the greatest global threat to health in the 21st century”.1 The current most accepted model for assessing the ecological impact of businesses and healthcare systems is carbon footprint quantification.2 This calculation is the sum of direct and indirect greenhouse gas emissions resulting from a specific activities and processes, and its result is expressed in kg of CO2, as this gas represents 80% of emissions.3

Renal replacement therapies have a significant impact on the carbon footprint of healthcare systems, especially in terms of supply chains and waste management.4 Hemodialysis is one of the main contributors to energy consumption, greenhouse gas emissions, water consumption, and waste generation within the healthcare system.5 Even if peritoneal dialysis (PD) consumes less water/energy than hemodialysis, it also generates a significant amount of plastic waste (tubing, bags) and logistical transport emissions. Establishing new management strategies based on greener nephrology is therefore essential for carbon footprint reduction.6

Apart from renal replacement therapy, CKD patient care has a further environmental impact due to the need for periodic visits to centres and the use of refrigerated or injectable medications that require increased waste management and electricity compsumption.7 Even though every drug has an environmental impact, oral option's footprint is primarily driven by manufacturing (pharmaceutical industry emissions) and packaging (blisters/boxes), rather than the frequent patient transport associated with hospital-administered injectables or the energy consumption linked to refrigeration. Erythropoiesis-Stimulating Agents (ESAs) like Darbepoetin alfa require cold storage, and subcutaneous administration with frequencies ranging from weekly to monthly, necessitating specific logistical arrangements (hospital pharmacy collection or administration visits) that contribute to the carbon footprint.

Choosing a more environmentally friendly treatment for ACKD-related pathologies can have a positive impact on the amount of waste generated and energy consumed. Our objective was to compare the carbon footprint derived from the use of oral medication and subcutaneous injectable treatments (darbepoetin alfa) in patients with ACKD or on peritoneal dialysis, aiming to prescribe treatments tailored to patient needs and reduce the carbon footprint in the future. We hypothesized that the carbon footprint associated with subcutaneous hospital-dispensed treatments would be significantly higher than that of oral pharmacy-dispensed treatments, primarily driven by transportation, energy consumption due to refrigeration and waste management, and patient mobility requirements.

In this observational, cross-sectional, single-centre, non-interventional study we compared two cohorts (both including patients with either ACKD or on PD) receiving hospital-dispensed medication. One group received oral medication (cinacalcet) and the other group received a subcutaneously administered erythropoiesis-stimulating agent (darbepoetin alfa). Cinacalcet was indicated for treatment of hyperparathyroidism secondary to chronic kidney disease, while darbepoetin alfa was indicated for anaemia secondary to chronic kidney disease. The study was approved by the Institutional Review Board of the Hospital Clínico Universitario de València (2022/306), and informed consent was obtained from all patients.

Patients collecting medication between 1st February and 1st May 2023 were selected for study using the following inclusion criteria: patients on a PD programme or with ACKD (estimated glomerular filtration rate<30ml/min/1.73m2), aged 18 and above, and capable of signing informed consent (Fig. 1). Clinical and demographic data were obtained through patients’ electronic health records, and carbon footprint-related data were collected through surveys with targeted questions (Supplementary material). We adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. A completed STROBE checklist is provided (Supplementary material).

Fig. 1.

Flowchart.

Of the 50 patients initially evaluated, 41 patients were included (Fig. 2). Patients included had a median age of 72 years [IQR 63–80]; 65% were male, 66% (28) were on peritoneal dialysis, 34% (13) were ACKD patients. 19 were undergoing treatment with cinacalcet (oral), and 22 were treated with darbepoetin alfa (subcutaneous).

Fig. 2.

Global carbon footprint of darbepoetin alfa and cinacalcet. * p<0.05.

Patients baseline characteristics according to treatment group are presented in Table 1.

The carbon footprint derived from the subcutaneous treatment process with darbepoetin alfa was 95,512.93kg of CO2/year, compared to the 12,199.85kg of CO2/year generated from treatment with cinacalcet (p-value 0.00). The contribution of each analyzed group to the carbon footprint is shown in Fig. 2.

The group with the greatest impact on the carbon footprint was transportation of erythropoiesis-stimulating agents (ESA), at 42,224.55kg CO2/year compared to 11,399.85kg CO2/year derived from cinacalcet consumption.

There were no significant between-group differences in carbon footprint from patient travel to the hospital for medicine collection (Table 2).

The second-largest contribution to the carbon footprint was derived from darbepoetin waste management, resulting in 55,001.42kg CO2/year, compared to just 800kg CO2/year with cinacalcet, due to sharps and needle processing and disposal (Fig. 2 and Table 2).

The median carbon footprint in waste generation for patients taking cinacalcet was lower, at 36.4kg CO2/year (IQR 36.3–36.5) compared to patients treated with darbepoetin alfa at 132kg CO2/year (IQR 93.5–143) with a p-value<0.00 (Table 2).

Finally, the only energy-related variable calculated was darbepoetin alfa refrigeration, with total emissions amounting to 8286.96kg CO2/year (Fig. 2).

Our results show that the carbon footprint of darbepoetin alfa (subcutaneously administered medication) is significantly higher than that of cinacalcet treatment (oral medication), largely driven by refrigerated transport and waste disposal, indicating a lower environmental impact for the oral administration route.

Carbon footprint modelling is a potentially fundamental tool in hospital management to reduce the environmental impact of medical treatments. The healthcare sector should take the lead in promoting sustainable practices, since changes in high-volume procedures could have a particularly significant impact on emissions.7

However, research on this area is scarce. Our findings align with existing literature comparing different drug administration pathways. For instance, Bouvet et al. MC highlight that oral administration results in significantly lower carbon emissions and water consumption.9 A randomized noninferiority trial found that emissions for comparable phosphate replacement in critically ill patients, were 60-fold less for the enteral route (14.2g of CO2e) compared to the IV route (843g of CO2e).10

To date, this is the first study to compare the carbon footprint of subcutaneous and oral administration treatments in patients with ACKD or on PD. The comparison refers strictly to the environmental footprint of the administration process, not the clinical equivalence of the drugs.

Although no studies have calculated the carbon footprint of patients in pre-dialysis-phase CKD, several have analyzed this problem in patients on hemodialysis due to the great impact of this treatment, particularly the high water use. Studies of ways to reduce carbon footprint in haemodialysis units are centred mainly in the United Kingdom, where a list of guidelines for more sustainable practices has been published, focused on patient, staff, and supplies transportation, reducing energy expenditure and improving waste management via reduction, reuse, and recycling.11 In addition to reducing the carbon footprint of the British healthcare system, implementing these guidelines would result in a saving of one billion pounds.12 Our study shows that the use of oral medication, even if dispensed by hospitals, can reduce the carbon footprint of each of these variables and improve the sustainability of renal treatments.

The main limitations of this study are the lack of national-level studies on carbon footprint in the healthcare sector, the difficulty in obtaining data, and that emissions from medication production were likely underestimated due to the absence of available data for carbon footprint calculation. Nonetheless, the clear difference in carbon footprint between the two treatment types strongly suggest that oral treatments are more sustainable.

Another limitation is the small simple size. While the observational nature of the study and the absence of exceptional interventions could theoretically have allowed for a larger cohort, this work was conceived as a pilot study intended to explore the feasibility and applicability of hybrid life-cycle assessment models in nephrology practice.

This study should be regarded as a pilot study for comprehensive carbon footprint calculation from the ground up, with the objective of analysing and standardizing this parameter, thereby initiating measures to curb the acceleration of climate change. These measures are aimed at reducing the carbon footprint of renal treatments in hospital nephrology departments. Multicentre prospective studies, preferably using a similar methodology to that of our research, are imperative to validate our findings.

In conclusion, choosing an oral administration treatment in patients with ACKD or PD can reduce the carbon footprint derived from their medical treatment by as much as 85%. The overarching goal is to establish environmentally sustainable practices that contribute towards the ultimate target of net-zero carbon emissions. Focused not only on economic considerations and advancing eco-friendly medical practices, this initiative also strives to enhance clinical care and improve patient outcomes.

The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript and there is no financial interest to report. We certify that the submission is original work and is not under review at any other publication.

The data underlying this article will be shared on reasonable request to the corresponding author.