Paper 1: What is the environmental footprint of a dental practice; A Life Cycle Analysis

doi:10.21203/rs.3.rs-3214976/v1

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Paper 1: What is the environmental footprint of a dental practice; A Life Cycle Analysis

https://doi.org/10.21203/rs.3.rs-3214976/v1

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Introduction: Growing awareness of environmental sustainability is essential. The IPCC's report stresses urgent carbon reductions to limit global warming to 1.5°C. The NHS in all four countries of the UK aims to be net-zero. Dental practices must prioritize sustainability for public health. This paper uses Life Cycle Analysis (LCA)where possible to study the dental practices' environmental footprint.

Methodology: LCA methodology was used where possible to calculate the carbon footprint of a full-time dental clinic operating 220 days/year. Ecoinvent database and OpenLCA software were used to calculate GHG emissions, normalized factors, and DALYs. Attributional and spend-based approaches were used to analyze procurement items.

Results: Compared with our 2015 paper, the 2023 carbon footprint, which used more current impact factors shows reduced water use emissions and increased total waste emissions. Staff travel and patient travel continues to significantly impact the carbon footprint. 99% of an average dental practice's health impact is from climate change.

Discussion: Addressing waste and promoting low-carbon transport within the dental practice is crucial. Procurement's impact requires detailed analysis. Normalized scores highlight the environmental impact compared to an average person.

Conclusion: The carbon footprint of a dental practice was updated using more current impact factors, to reinforce the high contribution of travel within the dental CFP, with an increase in the CFP of waste, and a reduction in the CFP of water

Health sciences/Health care/Dentistry/Dental public health

There is a growing awareness of the critical need for environmental sustainability in all aspects of our lives. The sixth synthesis report of the Intergovernmental Panel on Climate Change (IPCC) highlights the importance of immediate and significant reductions in carbon emissions to achieve the target of limiting global warming to 1.5°C.¹

The UN Sustainable Development Goals (SDGs) have been adopted by all United Nations Member States and established a collective framework for promoting peace and prosperity for both humanity and the planet. Central to this are the 17 Sustainable Development Goals (SDGs), which serve as a pressing call to action for all nations to engage in a global partnership. These goals recognize that the eradication of poverty and other forms of deprivation must be pursued alongside strategies that enhance healthcare and education, reduce inequality, stimulate sustainable economic growth, address climate change, and safeguard our oceans and forests.²

The National Health Service (NHS) in England recognizes the urgency of this challenge and aims to become the first net zero national health service in the world. As a part of the NHS, dentistry is obligated to align with the broader healthcare service's direction for several reasons, primarily because it is the ethical thing to do. Environmental damage has a direct impact on our health, making it imperative to prioritize sustainability efforts. In the UK 2013, the enactment of the Public Services (Social Value) Act made it mandatory for public service commissioners to consider broader societal, economic, and environmental benefits in addition to fulfilling public services. This act has influenced the inclusion of environmental sustainability within NHS procurement, with dental teams in England bidding for NHS contracts expected to demonstrate their sustainability credentials.

Measuring environmental impacts can be done in various ways, including accounting which evaluates an organization's greenhouse gas (GHG) emissions generally using the environmentally extended input output analysis (EEIOA)., or for example through a Life Cycle Assessment (LCA) approach. The EEIOA uses a spend-based approach which determines emissions by multiplying the financial value of a purchased good or service with conversion/emissions factors. However, this approach may lack specificity as emission factors are based on average industry greenhouse gas emissions. For example, using this methodology an upmarket product would be considered to have a much higher environmental footprint than a budget product, regardless of their sustainability impact.Process-based LCAs use an activity-based approach, using data on components of items and processes, such as distance travelled or material weight to quantify the environmental footprint of a product. Conversion factors for activity-based calculations are often obtained from scientific studies. Though more specific than EEIOA, collecting activity-based data for LCA can be challenging and time-consuming. To overcome these challenges, the widely-used carbon calculation standard, the Greenhouse Gas Protocol, recommends using a hybrid methodology. This approach utilizes as much activity-based data as possible and uses a spend-based method to estimate the remaining emissions. ³,⁴

It has been ten years since the former Public Health England commissioned the Centre for Sustainable Healthcare to analyse data looking at the carbon footprint of the NHS dental service.⁵ In recent times, the urgency to decrease our impact on the environment has grown due to heightened predictions about the outcomes of climate change. There have also been changes in the approach in calculating product or system environmental footprints, with an increasing emphasis on employing a more comprehensive Life Cycle Assessment (LCA) methodology. The use of LCA allows for the inclusion of additional factors such as water usage, air quality, and other impact indicators in the assessment of the dental environmental impact and fits well with the need to consider the SDGs in environmental accounting. 1^, ⁶

The NHS England carbon footprint for dentistry as published by PHE used a hybrid approach that combined elements of EEIOA and process-based LCA.4 Since this time, the main author of this paper (BD) has conducted several process-based LCAs looking, amongst other things, at different waste processes for specific dental waste streams. These LCA results suggest that GHG estimates of the PHE study should be revisited. Additionally, the carbon intensity of UK electricity is rapidly decreasing since 2015 due to the phasing out of coal and increased use of renewable energy sources⁷.

The aim of this paper was to;

Investigate any changes in CFP factors since the original study was conducted and consider additional LCA impact factors that might apply to dentistry.
Provide a more current figure for the CFP of an average full time dental practice (which will in turn feed into the simple CFP calculator we describe in the second CFP calculator paper in this journal)
Use LCA methodology where possible to also provide additional information on the human health impact of a dental practice (e.g. DALY, Disability Adjusted Life Years)

Functional unit

The functional unit within this LCA was a full-time dental clinic with one clinician, and one dental nurse and half a receptionist practicing full time and operating 220 days a year

Assumptions/Data sources

The Ecoinvent database was used and OpenLCA software to calculate the GHG emission factors (in this case the carbon footprint), alongside normalised factors, and DALYs.⁸,⁹ To estimate the carbon footprint of an average dental practice, and to keep with the functional unit it was assumed that the clinic and its staff worked full time , 220 days a year, and, based on data of the PHE England study saw on average 2654 patients. The following assumptions were used to estimate the environmental footprint as seen in Table 1. For all units used to calculate the environmental footprint see Appendix 1.

Table 1: Assumptions and data sources

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Data analysis:

A hybrid approach was undertaken:

For non-procurement items an attributional life cycle assessment (LCA) was conducted using mass-based physical allocation. The LCA was performed using OpenLCA v2.0 software and the Ecoinvent v3.91 reference database. The methodology of the LCA followed the recommendations of the International Standard Office and the European Commission's Product Environmental Footprint guidelines (ISO, European Commission, 2018).8, ¹⁰,¹¹The main outcome of the LCA was a life cycle impact assessment (LCIA) consisting of 16 environmental impact categories. Each impact category and its corresponding LCIA method and units have been described in other papers.¹²

For procurement items a spend-based approach was used to determine GHG emissions by multiplying the financial value of all purchased goods/non-financial services with emission factors provided by DEFRA.¹³

Secondary outcomes included the following:

(1)Normalized LCIA results:

The LCIA results were normalized against the annual environmental footprint of an average dental practice to enable comparison between impact categories. As per the Product Environmental Footprint guidelines, toxicity categories were excluded from normalization while the LCIA methods were under review. Impact categories with higher normalized values hold more significance in the overall environmental footprint compared to categories with smaller normalized values.

(2) Burden of human health:

The burden of human health was assessed in disability-adjusted life years (DALYs), which represent the number of years of life lost in the human population due to morbidity (disease and disability) and mortality (death) (WHO, 2020). LCA modelling was employed to calculate DALYs lost across the global population based on impact categories related to human health, using the ReCiPe 2016 Endpoint (H) method.¹⁴

Contribution analysis:

A contribution analysis for carbon dioxide equivalent emissions was conducted to determine which aspect of each product's life cycle contributed the most to the environmental impacts.

Annual carbon footprint of a dental practice (kgCO2e) – 2015 v 2023

The results (all in kg CO2eq) can be seen in Table 2

Table 2 illustrates by changing the way we calculate our footprint, that the carbon emissions of water use decreased (from 0.143 to 0.037%). Total waste increased from 0.323% to around 1%. The CFP of electricity decreased from around 8% to 4.7%, although natural gas stayed almost identical. Using full time equivalent assumption staff travel for work, and to work increased from around 27% to 35%, with patient travel reducing from 33% to 26%

With changes in the procurement conversion factor there was little change in the procurement footprint (from around 20% to 21%)

Table 2: Annual carbon footprint of a dental practice (kgCO2e) – 2015 v 2023

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Figure 1 provides a graphical example of Table 1

Figure 1: Annual carbon footprint of an average Dental Surgery using 2014 and 2023 methodology

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Sensitivity Analysis (Staff travel)

Table 3 shows the change in the UK CFP when staff were assumed to travel using UK modes of travel. KgCO2e

Table 3: Sensitivity Analysis; three different assumptions and the carbon footprint (KgCO2e)

Insert Table 3 here.

Figure 2 shows the three different carbon footprints based on

1: 2015 methodology/carbon footprinting;

2: 2023 methodology; assuming all staff travel by car and

3: 2023 methodology assuming staff travel by mixed UK modes

Figure 2: Sensitivity Analysis; three different assumptions and the carbon footprint (KgCO2e)

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DALYs

Table 4 shows the annual? DALY results for an average dental practice of NHS England.

99% of the annual human health impact of an average dental surgery, 0.0328 out of 0.033 DALYs, is due to climate change with much less of an impact from other factors such as water consumption etc

Table 4: Annual human health impact (DALYs) of an average dental surgery in the NHS

Insert table 4 here

Normalised Scores:

Table 5 shows the normalised scores, demonstrating that the average dental practice’s impact on freshwater ecotoxity is equivalent to the impact on freshwater ecotoxity of 17 average people, the equivalent of around 5 persons’ annualised carbon footprints.

Table 5: Normalised Scores:

Insert table 5 here

The 2023 annual carbon footprint of an average dental surgery is not based on primary data from 2023. Instead, it reconstructs the information gathered from a comprehensive study conducted a decade prior. While it would be beneficial to acquire more extensive primary data on procurement, travel, energy, waste, and other factors, it would necessitate a well-funded research endeavour. In the absence of such resources, we have adjusted our 2015 comprehensive dataset to account for inflation and re-evaluated our data modelling approach. By utilizing up-to-date Life Cycle Assessment (LCA) methodology and more recent emission factors, we have generated an updated estimation of the annual carbon footprint of an average dental practice.

The 2023 carbon footprint, shows a notable increase in the proportion of patient travel, while staff travel remained relatively consistent due to the use of different databases.

Travel

As in the original study, the GHG emissions associated with patient travel, were based on indirect emissions (including the building and maintenance of the car/bus/train and allocation of the vehicle and well-to-tank emissions) as well as the direct emissions, tailpipe emissions for the miles travelled which amounts to 0.5489 kg CO2e per mile.¹⁵. In the PHE study we used Small World Consulting figures (0.5275 kg CO2e per mile of car travel) For all travel we used a figure of 220 days (to match other studies by Duane, Lyne, Ashley¹⁶,¹⁷,¹⁸. Patient travel did not change to any degree. There were however a number of differences in the way staff travel was calculated in this study. The PHE paper utilized a questionnaire from NHS Fife to gather data on the distances travelled by various types of staff (e.g. dental therapist, dental nurse, receptionist, etc.), showcasing the differences in travel distances among these professionals.¹⁹,²⁰ Using national information on staff numbers total distances were aggregated for dental therapists, dental nurses etc. Within this calculation for simplification a broad average of 42.6 miles return per day for staff travel was used. For staff travel in the Fife study (Duane 2011)6, we determined from the staff questionnaire that most of the travel to dental practices was based on cars, 99%, and copied this methodology in the English study. This assumption for the broader UK could be potentially flawed so we also undertook a sensitivity analysis to investigate the scenario where staff travelled by UK travel modalities (ie an average mixture of car, bus etc). The two different scenarios amounted to an increase of 2351kgCO2emissions if staff travelled using usual UK travel modes.

In this study, the main reason for changes in staff travel was that our functional unit was for full time staff; we did not alter the distances for part time workers, or NHS allocation, as our aim was to calculate a CFP for a FT practice. This change led to an increase in this CPF from 7398 kgCO2e (2015) to 12427 kgCO2e (this paper)

Within dentistry the CFP of patient and staff travel continues to be much higher than in other non-primary care health settings. The dental team needs to consider how they can incentivise patients and staff to use low carbon transport options for travel to their practices and we discuss this in more detail in our travel literature.²¹,²²

Procurement

Procurement is a little higher in this analysis than the 2015 study. This is mainly related to the changes in emission factors for procurement from DEFRA as well as changes in the ratio of providing performers to performers only/Associates²³. To reduce the GHG emissions associated with dental procurement, a more detailed carbon footprint analysis is required to identify the dental procurement carbon hotspots. Currently, there is very little information known on the GHG emissions associated with dental laboratory work and materials and using LCA methodology to fill this gap would be time consuming but is necessary.

Waste

The carbon footprint of waste has increased from 0.32% to around 1% of the overall CFP based on LCA methodology. The CFP of domestic waste used in this calculation was based on standard Ecoinvent municipal (household waste) and included transport. To calculate the amalgam waste, we consulted a paper from Q, but assumed that the amalgam was 100% mercury as most of the impact from this waste would come from the more toxic element. The contribution of amalgam waste to the total carbon footprint of a dental practice is negligible and it is suspected in any respect that the amount of amalgam waste will reduce with the changes in its use.²⁴,²⁵

The calculation of the CFP of dental medical waste is more complicated. To estimate the potential CFP of waste, the authors looked at Richardson’s paper which estimated the types of paper, plastic etc produced from a dental clinic.²⁶ Ecoinvent data bases were used to calculate a mix of incineration types based on these proportions. The CFP calculated included energy generation from incineration of such a mix of products and was 1552 kg Carbon/ tonne, which is lower than the figure used in our Fife study (1.8kg) but higher than the medical waste figure recently calculated by Rizan (who calculated high temperature incineration was 1074 kg CO2e/ t).²⁷ There might be a number of reasons for this.

We included the energy use of shredding (48 gram carbon); which did not seem to be present in Rizan’s paper but may have been included in other processes.
In this calculation our mix of material (paper, plastic etc) was specific to dentistry, and is assumed to be reflected in medical waste. leading to a different environmental impact than medical waste in hospitals

The environmental footprint of dental waste is higher than we thought, and higher than originally calculated in 2014 and highlights the need for dental teams to consider how they manage waste. As Rizan suggests (shredding) and autoclaving the waste and then recycling the waste will significantly reduce this footprint.44

As Table 2 shows the carbon emissions of water use decreased from 25 Kg to 12.8 kg

The water use, both in 2015 and now, is based on a very limited sample sizes (based on the average water use of a community dental service in Fife from 2010). More information is needed to verify this water use within dental practices.

This is the first LCA undertaken to look at the environmental impact of a dental practice. It includes the carbon footprint of procurement, but excludes the other environmental impacts associated with buying goods and services. The calculation of procurement poses a challenge to calculate carbon emissions based on financial or expenditure data. In medical-based carbon footprint calculators, various expense categories such as pharmaceuticals or linen can be assigned different impact factors. However, in dentistry, due to the wide range of product types, this becomes more challenging. It is necessary to establish better proxies for procurement and conduct more detailed Life Cycle Assessment (LCA) calculations. However, such endeavours go beyond the scope of the current workstream. In reality, to calculate procurement, we would require data on quantity, detailed ingredients, place of manufacture, transportation etc, for every product we use. Ideally, by purchasing an item with a known carbon footprint, the amount of carbon emitted could be automatically calculated and integrated into an accounting software process. However, we are still far from implementing such an approach.

Normalised results provide a snapshot of how the often-confusing impact categories compare with what an average human being (often referred to as an average Jo/e) would have on the environment. An average dental practice has around 4.7 times the carbon footprint of Jo(e). However, its greater impact is from its impact on freshwater ecotoxicity, the majority of which originates from fossil fuel derived travel, and is equivalent to 17 times what an average person would contribute within a year. Material resources (4.3X), photochemical oxidant formation (2.8X), and acidification (1.7X) all result from the high travel component.

The average dental surgery’s contribution to DALYs came mainly from the human health impact of climate change (12 days of DALY). A single Disability-Adjusted Life Year (DALY) signifies the deprivation of one year of overall well-being. Based on our results, the activities of a dental practice over one year could be assumed to cause 12.05 days of Disability adjusted life year, per practice. Like the other impacts, this is mostly due to travel and travel associated harm (e.g. cardiovascular impact, respiratory impact) which is now well publicised.²⁸

This paper provides a sense check of the work carried out in 2015. This update shows that although travel related GHG emissions are still high, the proportion of energy has reduced. The impact of waste in the carbon footprint was understated in our 2015 work. The importance of procurement has increased slightly due to changes in conversion factors.

Practice points:

Although no new data was collected for 2023 clinicians should note that due to changes in methodology/emission factors the following changes occurred;

The overall CFP has increased from 27 tonnes to 35 tonnes
The proportion of waste has increased to 1% of the CFP
The contribution of travel has increased, particularly staff travel

Ethics declaration

This research involves information freely available in the public domain eg published and secondary data, so does not require ethical approval.

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Tables 1-5 is available in the Supplementary Files section.

There is no duality of interest

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Editorial decision: revise
26 Sep, 2023
Review #2 received at journal
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Review #1 received at journal
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Reviewer #2 agreed at journal
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Reviewer #1 agreed at journal
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You are reading this latest preprint version

Paper 1: What is the environmental footprint of a dental practice; A Life Cycle Analysis

Status:

Version 1

Abstract

Figures

Introduction

Methodology

Functional unit

Assumptions/Data sources

Data analysis:

Results

Annual carbon footprint of a dental practice (kgCO2e) – 2015 v 2023

Sensitivity Analysis (Staff travel)

DALYs

Normalised Scores:

Discussion

Travel

Procurement

Waste

Conclusion

Practice points:

Declarations

Ethics declaration

References

Tables

Additional Declarations

Supplementary Files

Status:

Version 1