METHODS
Variables contributing to carbon emissions were identified and quantified. The carbon footprint was
evaluated based on the total emissions produced during two RT regimens: 50 Gy in 25 fractions (longcourse
radiotherapy, LCRT) and 25 Gy in 5 fractions (short-course radiotherapy, SCRT).
RESULTS
A total of 12 patients participated in the study, with a mean age of 68.5±13.83 years. Among them, 83.3%
(n=10) were male. The overall carbon footprint from all procedures was calculated as 168.6±85.4 kg
CO?e (carbon dioxide equivalent) per patient. The mean emission for SCRT was 105±9.4 kg CO?e, while
for LCRT it was 231.4±80.6 kg CO?e per patient?a statistically significant difference (p=0.004). Inpatient
treatment resulted in lower carbon emissions than outpatient treatment. The highest contributors
to carbon emissions in both groups were radiotherapy and imaging procedures, followed by transportation,
electricity use, and heating systems.
CONCLUSION
The study concluded that SCRT, inpatient treatment, proximity of patients" residences to the hospital,
and the use of public transportation were associated with reduced carbon footprint values.
Keywords: Carbon footprint; greenhouse gases; radiotherapy; rectum cancer
Within the healthcare system, greenhouse gas
emissions arise from various sources, including patient
transportation to hospitals, diagnostic imaging
and treatment procedures, hospitalizations, use of
medical and non-medical equipment, electricity consumption,
materials used by both patients and staff,
heating and cooling systems, anaesthetic gases, and
waste generation.[
In healthcare systems where greenhouse gas emissions
are significant, the rate may be even higher in cases
such as colorectal cancer, which require prolonged
hospital-based treatment processes.[
This study was conducted to help fill that gap and
guide future research. Our aim was to examine the
treatment protocols used for rectal cancer patients and
to explore potential strategies for reducing the greenhouse
gas emissions associated with these protocols.
Ethical Approval
This study received unanimous approval from the Scientific
Research Ethics Committee of Erzurum Faculty
of Medicine (No: 2024/182, Date: 11/09/2024). The
study was conducted in accordance with the declaration
of Helsinki.
Study Design
The study included patients diagnosed with locally advanced
stage 3 rectal cancer, who were ineligible for
chemotherapy and received radiotherapy between October
1, 2024, and December 31, 2024, at the Radiation
Oncology Clinic of Erzurum City Hospital. The patients
were divided into two groups, with each group receiving
one of two radiotherapy modalities: Short-course
radiotherapy (SCRT) administered over 5 days (25
Gy/5 fractions) and long-course radiotherapy (LCRT)
administered over 25 days (50 Gy/25 fractions).
All patients in the LCRT group and 50% of patients in the SCRT group were admitted to the palliative care service, and their data were followed up by family physician.
Greenhouse gas (GHG) emissions resulting from hospitalization, travel, and medical procedures-including radiotherapy, imaging, interventions, waste disposal, and the consumption of electricity and natural gas during hospital stays-were calculated for each patient in accordance with the Greenhouse Gas (GHG) Protocol Standards and TS EN ISO 14064 Greenhouse Gas Inventory Standards.
The study included a total of 12 patients: Six received LCRT and six received SCRT. The contributing factors to carbon emissions during the treatment period were identified, and the total carbon emissions associated with each radiotherapy modality were compared. The primary objective of the study was to determine which radiotherapy approach resulted in lower carbon emissions.
Patient Selection
All patients who presented for radiotherapy with a
diagnosis of locally advanced stage 3 rectal cancer between
October 1, 2024, and December 31, 2024, and
who met the inclusion criteria were enrolled in the
study. Inclusion criteria were diagnosed with locally
advanced stage 3 rectal cancer, followed up at Erzurum
City Hospital, aged between 18 and 80 years, provided
voluntary informed consent. Exclusion criteria included;
presence of acute cerebrovascular events (CVEs) or
other neurological conditions affecting mental status,
psychiatric disorders, hemiplegia or hemiparesis in the
extremities, aphasia, severe visual or hearing impairments,
being in the postoperative recovery period. Patients
who did not receive concurrent chemotherapy
were selected to ensure uniformity in radiotherapybased
carbon emission assessment.
Data Collection and Emission Factor Sources
Data on carbon emissions produced by patients during
the radiotherapy process were collected and calculated
under the following categories:
Carbon Footprint of Radiotherapy
Radiotherapy for rectal cancer is typically delivered
in treatment fractions ranging from 5 to 25 sessions.
The carbon footprint of radiotherapy (RT) is calculated
by multiplying the fixed emissions associated with
the device by the number of treatment fractions and
adding the carbon emissions resulting from sulphur
hexafluoride (SF6) leakage. The fixed component refers to the carbon emissions generated by the electricity
consumed per treatment fraction, while the variable
component corresponds to the total number of
planned fractions.[8]
Patients in this study were treated using a tomotherapy device. The electricity consumption of this device was measured at 0.822 kWh per minute. According to Türkiye"s national greenhouse gas inventory, 1 kWh of electricity consumption results in 0.439 kg CO2e emissions. Because treatment durations varied between patients, the carbon dioxide emitted during each patient's total radiotherapy session was calculated individually. Furthermore, the annual SF6 leakage from the tomotherapy unit was estimated, and the per-fraction SF6 emission was calculated separately for each patient.
Carbon Footprint of Imaging Methods
Carbon Footprint of Patient Travel
Travel distances were calculated using Google Maps,
and self-reported information regarding travel routes
and vehicle types was used. Emissions were estimated
using the IPCC 2006 Tier 1 method, the GHG Protocol,
and ISO 14064-1 standards. The following assumptions
were applied; average fuel consumption of
a diesel car: 7.3 L/100 km, average fuel consumption
of a diesel bus: 29.9 L/100 km. Carbon emission per
Liter of diesel consumed: 2.54 kg CO2e.[
Carbon Footprint of Electricity Consumption and
Heating
Carbon Footprint of Patient Treatment and Hospitalization
• Medical consumables included: Cotton, bandages,
compresses, blood sampling materials, needles,
tubes, gloves, urine rapid tests, masks, tongue depressors,
infusion sets, face masks.
• Medical equipment included: Electrocardiograms,
thermometers, glucometers, otoscopes, scales,
flashlights, stethoscopes, and sphygmomanometers.
• Non-medical consumables included: Paper, toner,
and paper towels.
• Non-medical equipment included: Computers,
printers, and some other electronic devices.
• Waste materials included: Paper, plastic, glass, and
hazardous waste.
Carbon emissions for all these items were estimated
based on the UK Government's 2024 Greenhouse Gas
Reporting Conversion Factors.[
Data Collection Tools
Data Collection
Radiotherapy-related data for outpatients were recorded
daily by a health physicist, who also performed
the corresponding carbon emission calculations. For
inpatients, data regarding medical treatments, diagnostic
examinations, medical and non-medical materials,
and equipment usage were recorded by the
family physician, and associated carbon emissions
were calculated accordingly. Data on electricity and
heating consumption in patient rooms were obtained
from the hospital"s health services directorate and
technical department (Fig.
Population and Sample of the Study
All patients who met the inclusion criteria, did not
meet any exclusion criteria, and voluntarily agreed to
participate were included in the study sample.
Data Analysis
To compare two independent groups, the student"s
t-test was employed for variables showing normal distribution,
whereas the Mann-Whitney U test was applied
for variables not meeting normality assumptions.
The Chi-square test was used to compare categorical
variables between groups. A p-value of less than 0.05
was considered statistically significant.
All patients underwent positron emission tomography-
computed tomography (PET-CT), computed tomography
(CT), magnetic resonance imaging (MRI),
colonoscopy, and CT simulation prior to radiotherapy.
The carbon emissions resulting from these imaging
procedures were assumed to be the same for all patients
and were incorporated into the total emission calculations
accordingly. The average duration of a PET-CT
scan was 15 minutes, with an electricity consumption
of 1.33 kWh per minute. The CT simulator and CT
device each consumed 1.33 kWh per minute as well.
The MRI device consumed 0.3155 kWh per minute.
For colonoscopy, which was considered part of the diagnostic
phase, an approximate carbon emission value
was calculated and included in the total emissions.[
The carbon footprint related to patient travel was calculated
based on the distance between the patient"s
residence and the hospital, the type of vehicle used,
and the fuel consumption rate. Among the 12 patients,
seven were from four provinces outside Erzurum
(Ağrı, Ardahan, Manisa, and Iğdır), while five resided
in districts within Erzurum (Çat, Aziziye, Yakutiye,
Palandöken, and Pasinler). Nine patients were hospitalized,
and their travel emissions were calculated as
a single round trip (from home to hospital and back
after discharge). Three patients received outpatient
treatment, and their emissions were calculated for five
days of commuting to and from the hospital. Patients"
residential addresses were obtained from hospital records
and verified through face-to-face interviews.
Carbon emissions resulting from the electricity and
natural gas consumption in patient rooms during hospitalization
were calculated using data from national
greenhouse gas inventories. On average, 1.5 kWh of
electricity was consumed per day per room. Based
on Türkiye"s emission standards, 0.478 kg CO2e is released
per 1 kWh of electricity. Additionally, 0.82 m³
of natural gas was used daily for heating, producing
2.1857 kg CO2 per 1 m³ of natural gas. All emission
calculations were performed according to the relevant
national inventory data.[
Carbon emissions associated with patient care and
hospitalization were calculated based on the following
categories: Medical consumables, non-medical
consumables, medical equipment, non-medical equipment,
waste, and laboratory procedures.
Personal Information Form
The personal information form was developed by the
researcher following a comprehensive literature review.
[
Data were collected through face-to-face interviews
conducted by the researchers, after informing the patients
about the purpose of the study and obtaining
their consent. The following information was recorded
using the data collection form; Socio-demographic
characteristics, medical history, distance between residence
and hospital, type of transportation used.
The study population included all patients diagnosed
with stage 3 rectal cancer who were treated at the Radiation
Oncology Clinic of Erzurum City Hospital.
The study was conducted over the last three months
of the year and was extrapolated to represent an annual
estimate.
The collected data were analysed using SPSS version
26. The normality of continuous variables was assessed
using the Kolmogorov-Smirnov test. For normally
distributed continuous variables, results were
presented as mean ± standard deviation, while frequency
and percentage values were used to describe
categorical variables.
The distance from participants" residences to the hospital ranged from 3,6 km to 1593.3 km. Most patients (75%, n=9) used public transportation to reach the hospital, while 25% (n=3) used private vehicles. Regarding chronic diseases, 33.3% (n=4) had no chronic condition, whereas 66.7% (n=8) had at least one chronic disease. Specifically, 37.5% (n=3) had hypertension, 12.5% (n=1) had hepatitis, 12.5% (n=1) had diabetes mellitus, and 37.5% (n=3) had both diabetes mellitus and hypertension.
Income levels varied, with 25% (n=3) reporting
income lower than expenses, 66.7% (n=8) reporting
income equal to expenses, and 8.3% (n=1) reporting
income higher than expenses. A detailed comparison
of socio-demographic data and health history is presented
in Table
Mean CO2 emissions from medical treatments were 9.59±8.3 kg CO2e, from travel 56.46±59.49 kg CO2e, from electricity and heating 34.49±29.84 kg CO2e, and from radiotherapy 39.65±21.13 kg CO2e. All patients underwent colonoscopy, which accounted for an average of 28.4 kg CO2e emissions.
The total carbon footprint resulting from treatments was calculated as 2023.43 kg CO2e, with a mean of 168.6±85.45 kg CO2e (minimum 92.5 kg CO2e, maximum 392.94 kg CO2e).
The two treatment protocol groups were homogeneous
in terms of cancer type, stage, and other
variables, with no significant differences observed
(Table
Table
However, the median carbon footprint related to electricity consumption and heating was significantly lower in the 5-fraction group (6.27 kg CO2e; Q1-Q3: 0.0-12.54) compared to the 25-fraction group (62.72 kg CO2e; Q1-Q3: 62.7-62.7) (p=0.002).
Carbon Footprint Results of Radiotherapy
Detailed calculations for each patient are presented in
Table
Carbon Footprint Results of Imaging Methods
Carbon Footprint Results of Patient Treatment
and Hospitalization
Carbon Footprint Results of Electricity and
Heating Systems
Carbon Footprint Results of Travel
The average imaging time for PET CT was 15 minutes,
during which 20 kWh of electricity was consumed,
leading to calculated emissions of 8.78 kg CO2e. MRI
consumed 6.31 kWh over a 20-minute scan, corresponding
to 2.77 kg CO2e emissions. The electricity
consumption of CT and CT simulator devices was
measured as 1.33 kWh per minute, with an associated
carbon emission of 0.58387 kg CO2e per minute. The
average CO2 emissions from a colonoscopy procedure
were estimated at 28.4 kg CO2e.[
The average daily carbon footprint from medical
consumables was 0.6979 kg CO2e, resulting in a total
of 3.49 kg CO2e for a 5-day period and 17.45 kg CO2e
for 25 days. These values were calculated using emission
factors and conversion coefficients drawn from
the literature. For instance, gloves emitted 0.026 kg
CO2e per unit, masks 0.02 kg CO2e, bandages and compresses 0.28 kg CO2e, blood sampling materials
0.057 kg CO2e, and general medical waste 0.7 kg
CO?e. Medical equipment such as ECG devices and
otoscopes contributed approximately 0.02 kg CO2e
per unit. The mean daily consumption included 10
pairs of gloves, 2 tubes, 5 injection syringes, 1 mask,
and 0.6 kg of waste, which were recorded and used
for calculations.[
Natural gas consumption over 5 days was 4.1 m³, corresponding
to 8.96 kg CO2e emissions, while over 25
days it was 20.5 m³, producing 44.8 kg CO2e. Electricity
consumption over 5 days was 7.5 kWh, resulting in
3.59 kg CO2e, and over 25 days was 37.5 kWh, corresponding
to 17.93 kg CO2e.
Participants included two patients from Ardahan, two
from Iğdır, one from Manisa, two from Ağrı, and five
from districts within Erzurum. Detailed travel emission
calculations are provided in Table
Given the anticipated adverse effects of global
warming and climate change-including increased
mortality risk-it is plausible that treatment methods
which reduce carbon footprints may indirectly mitigate
these harms. Shortening the radiotherapy course
can lower emissions and treatment burden, while
also enhancing patient quality of life. Consequently,
such approaches could positively influence Disability-
Adjusted Life Years (DALYs) by simultaneously
improving cancer outcomes and reducing environmental
impact. Hypofractionation offers multiple
benefits, including reducing the carbon footprint,
shortening hospital stays, decreasing productivity
losses, and lowering infection risks. It also improves
patient comfort and decreases healthcare costs. Our
findings are consistent with those of Moore et al.,[
When examining SCRT patients, inpatient treatment
was associated with a lower carbon footprint
compared to outpatient treatment (Fig.
Our study also highlights the critical impact of
treatment centre proximity on carbon emissions.
Patients traveling long distances daily by private vehicle
incur higher carbon footprints. Therefore, it is
advisable to treat patients at centres close to their residences,
and where centres are lacking, new facilities
should be established. Among outpatients receiving
short-course radiotherapy (SCRT), those who used
public transportation had a lower carbon footprint
compared to those who travelled by private vehicle.
This finding aligns with the results reported by Frick
et al.,[
In our study, radiotherapy and imaging modalities
were the largest contributors to carbon emissions
during treatment, followed by travel-related emissions.
Heating and electricity consumption ranked
third, while medical and non-medical consumables
accounted for the smallest proportion (Fig.
Limitations
• The study included patients who did not receive
chemotherapy due to advanced age or comorbidities
to maintain homogeneity and isolate the effect
of radiotherapy. This criterion resulted in a
small sample size, reflecting the limited number
of eligible patients.
• SF6 leakage is typically calculated on an annual basis.
For this study, annual SF6 emissions were converted
to per-minute values to estimate leakage for
each treatment fraction virtually.
• The carbon footprint associated with hospital cleaning
during patient hospitalization was not included
in the calculations.
• Emission factors used in this study are countryspecific
and vary internationally. While this variability
is acknowledged, it is not expected to significantly
affect the core variables constituting
the carbon footprint. Calculations were based on
a general methodology intended to be applicable
worldwide, and findings were compared with international
studies. To date, no recent carbon
footprint studies in the healthcare field have been
conducted in Türkiye.
To further reduce emissions, clinic appointments should be coordinated and scheduled on the same day to minimize patient visits. For patients living far from treatment centres, hypo fractionated radiotherapy not only reduces the carbon footprint but also decreases hospitalization time. Additionally, establishing radiotherapy units in multiple locations connected to hospitals, but separate from main hospital buildings, can enable patients to receive treatment closer to home. If opening new units is not feasible, providing nearby patient accommodations, such as hostels, could be a viable alternative.
These findings offer valuable insights and can serve as a foundation for future initiatives aimed at lowering carbon emissions within the healthcare sector, promoting more sustainable healthcare delivery and living.
Ethics Committee Approval: The study was approved by the Erzurum Faculty of Medicine Scientific Research Ethics Committee (no: 2024/182, date: 11/09/2024).
Informed Consent: Informed consent was obtained from all participants.
Conflict of Interest Statement: The authors have no conflicts of interest to declare.
Funding: The authors declared that this study received no financial support.
Use of AI for Writing Assistance: No AI technologies utilized. Author Contributions: Concept - S.Z., A.Z.; Design - S.Z., A.Z., Y.Ö.; Supervision - S.Z., A.Z.; Data collection and/or processing - S.Z., A.Z., Y.Ö.; Data analysis and/or interpretation - S.Z., A.Z.; Literature search - S.Z., A.Z., Y.Ö.; Writing - S.Z.; Critical review - S.Z., A.Z., Y.Ö.
Peer-review: Externally peer-reviewed.
