The Greener NHS: Net Zero, Sustainability and Climate Change for Medicine Interviews

The Greener NHS is the programme driving the health service towards net zero. The NHS accounts for around 4 to 5 per cent of the UK’s carbon footprint and has two targets: net zero by 2040 for the emissions it controls directly, and net zero by 2045 for the emissions it can only influence.

I am Dr Akash Gandhi, an NHS GP who has prepared applicants for medical school interviews at TheUKCATPeople since 2012. Sustainability comes up in medicine interviews more often than students expect, and the questions are practical rather than political. Our medicine interview hot topics guide covers the wider picture, and this page takes this one topic in detail.

What is the Greener NHS?

The Greener NHS is the national programme responsible for cutting the health service’s carbon emissions and getting it to net zero. It works with trusts, staff and suppliers on energy, buildings, travel, medicines and procurement. The NHS committed to net zero in October 2020, the first national health system in the world to do so.

• The size of the problem: the NHS produces around 4 to 5 per cent of the UK’s carbon footprint and roughly 30 to 40 per cent of public sector emissions.
• Two targets, not one: 2040 for the emissions the NHS controls directly, 2045 for the wider footprint it can only influence.
• The biggest source: the supply chain, meaning medicines, equipment, food and construction, close to half the total.
• Where it is run from: inside NHS England, which is itself being folded into the Department of Health and Social Care. The targets belong to the NHS, not to one organisation. How the NHS is organised is a separate topic.

Key Takeaway: The Greener NHS has two deadlines, and the emissions it chases sit mostly in what the NHS buys.

Why does the NHS have a carbon footprint?

The NHS has a carbon footprint because delivering care uses energy, buildings, vehicles, gases and an enormous quantity of manufactured goods. Treating illness produces emissions, and those emissions go on to cause illness, so a health service has a clinical reason to cut them. Some of it is waste rather than care.

The example: at Hull Women and Children’s Hospital, staff found the pipes carrying nitrous oxide, the gas and air used in labour, were leaking almost all of it into the atmosphere before it reached a patient.

Disconnecting the valves until the gas was needed cut monthly emissions from 395 tonnes of carbon dioxide equivalent to 43, with no change to anyone’s pain relief.

Key Takeaway: The NHS is not a small emitter doing its bit. It is roughly a twentieth of the UK’s carbon footprint.

What are the NHS net zero targets?

There are two. Net zero by 2040 covers the emissions the NHS controls directly, and net zero by 2045 the far larger footprint it can only influence. Both are worth knowing, because the 2045 target covers the emissions the NHS controls least.

Both run from a 1990 baseline, and progress is uneven. Direct emissions are down 68 per cent since then, while the wider footprint is broadly where it was in 2019. Measured per hospital admission it has fallen 7 per cent, so the NHS is doing more at a lower carbon cost.

Key Takeaway: Say both dates, 2040 and 2045, and say what each covers.

Where do NHS emissions actually come from?

Most NHS emissions come from the things the NHS buys, not the buildings it runs. The table below is most of what you need, and the first row is the one that changes an answer.

Buildings and energy are about a tenth of the total. Personal travel, roughly 90 per cent of it by car, dwarfs the NHS fleet, one reason telemedicine and artificial intelligence in the NHS are sustainability questions as well as safety ones.

The supply chain row is where the policy sits. The NHS buys over 600,000 products from around 80,000 suppliers, so its strongest lever is being a customer big enough to change what it will buy.

• Net zero is scored in the tender: since April 2022 every new NHS procurement carries a 10 per cent weighting for net zero and social value.
• Carbon reduction plans are mandatory: required from April 2023 for contracts above £5 million a year, and for all new procurements from April 2024.
• Single use is being designed out: the Design for Life roadmap commits the NHS to a circular system for medical technology by 2045.

Every pound spent decarbonising is a pound not spent on treatment, the problem QALYs exist to referee, and it competes with winter pressures for capital.

Key Takeaway: The supply chain is close to half the footprint, so procurement is the biggest lever.

Which clinical changes cut the most carbon?

Changing anaesthetic gases and inhaler propellants has produced the fastest cuts the NHS has managed. Both are only about 3 per cent of the footprint, but a clinician can change them without rebuilding anything. Each is a small volume of gas with a very large warming effect.

• Desflurane: roughly 2,500 times more warming than carbon dioxide. NHS England worked with the Royal College of Anaesthetists to decommission it in favour of clinical alternatives in January 2023. Emissions are down 98 per cent, saving up to £4 million a year.
• Nitrous oxide: around 310 times more warming, and it lingers for about 150 years. The problem is not what patients breathe, it is what escapes. At one East Lancashire site, clinical use accounted for 0.26 per cent of the nitrous oxide passing through the manifold. Fixing that saves over £2.3 million a year.
• Inhalers: a pressurised metered dose inhaler fires a propellant, and the two in common use are about 1,300 and 3,350 times more warming than carbon dioxide. Inhaler emissions are down 33 per cent since 2019/20.
• The propellant switch: on 21 July 2026 the MHRA became the first regulator anywhere to approve inhalers using the propellant HFA-152a. Same drug, same doses, and propellants of this type cut an inhaler’s footprint by at least 90 per cent.

Medicines emissions are down a third in five years. In my own surgery the change that has made most difference is not the device at all. It is getting asthma control right, because a well controlled patient gets through far fewer reliever inhalers.

Key Takeaway: One dated example carries further than a general point, and desflurane at 98 per cent down is the most quotable.

How does climate change affect health in the UK?

Climate change mostly makes existing illnesses more common, more severe and more unequally spread, which is why doctors call it a threat multiplier.

• Heat: the UK Health Security Agency estimated 1,504 heat-associated deaths in England in summer 2025, after a record 2,985 in 2022. Death rates are highest by far in people aged 85 and over.
• Air quality: the fossil fuel use that warms the climate also degrades the air, driving asthma, lung disease and heart disease. Cutting emissions improves health now, not in fifty years.
• Infection and extreme weather: warmer conditions widen the range of diseases such as dengue, and severe weather disrupts care as demand rises.

None of it lands evenly. The burden falls on people already at the wrong end of the social gradient described in the Marmot Review of health inequalities.

Key Takeaway: Say threat multiplier, then give a UK example. Heat deaths in England are recent and checkable.

When do sustainability and patient care conflict?

They conflict whenever the greener option is worse for a particular patient, and naming that patient turns a slogan into an argument. Interviewers push here, so it is worth the most preparation.

• Desflurane was not withdrawn for being a bad drug: it wakes patients up faster than the alternatives, which some anaesthetists valued. It went because safe, cheaper alternatives existed, and exceptional use is still permitted.
• Banning nitrous oxide would take pain relief away from women in labour: the savings came from stopping leaks in the pipework, not from stopping patients using gas and air. Trusts kept it available through cylinders attached to the machine.
• Dry powder inhalers are not right for everyone: they need a fast, deep breath in, so they can be unsuitable for young children, frail older patients and anyone having a severe attack. Devices should not be changed without consulting the patient.
• Reusable is not automatically greener: a reusable instrument has to be collected, washed, sterilised and transported, so the advantage depends on how often it is genuinely reused. Infection control sets hard limits: in 2001 England briefly required single-use instruments for tonsil surgery over a variant CJD risk, then withdrew it after surgeons reported more bleeding.

Our guide to answering medical ethics interview questions sets out the pattern: name the benefit, name the patient who loses, then say what would change your mind.

Key Takeaway: Never argue for a green change without naming the patient it could harm.

How can I talk about sustainability in my medicine interview?

Start with something you have actually seen, then connect it to one national fact. Nothing a sixth-former does moves 27 megatonnes, so a small true observation is worth more than an inflated claim.

• Work experience or volunteering: how much packaging comes off one sterile pack, or how many people drove to an appointment that could have been a phone call.
• Your own GP surgery: ask why the practice changed inhaler brands, or what happens to medicines patients return unused.
• School projects: an eco committee or an EPQ on sustainable healthcare gives you something specific to describe.
• Your local trust’s Green Plan: every trust publishes one. Naming yours and one thing in it takes twenty minutes.

A structure that works for almost any sustainability question:

1. Answer the question in one sentence. Give your position before the detail.
2. Anchor it in one fact you can defend. The two target dates, or the supply chain share.
3. Add one example, ideally your own. Something you saw, asked about or read in a Green Plan.
4. Name the tension. Say who could be harmed by the green option, and what would change your view.

What interviewers are testing:

• Whether you have read past the headline: recycling is real, but the emissions are somewhere else.
• Whether patients come first: a green argument that ignores a patient is a warning sign.
• Whether you can hold two goods in tension: cost, carbon and care all matter at once.

The lowest carbon consultation is the one that never happens, which is why the sugar tax and the obesity crisis have a climate dimension too.

When I run mock interviews, the best answer I have heard came from a candidate who asked her GP why the practice changed inhaler brands. She could describe the conversation, including the patient who refused to switch.

Key Takeaway: One honest, specific observation from your own experience does more work than a list of targets.

Example interview questions on the greener NHS

You are unlikely to be asked any of these word for word, and you do not need a prepared answer to each one. Use them to check your understanding: if you could speak for a minute on most of them, you know this topic well enough for whatever the interviewer actually asks.

Questions to get you thinking

1. What is the Greener NHS, and why does a health service need a climate policy?
2. When is the NHS aiming to reach net zero, and how big is its carbon footprint?
3. Where do most NHS emissions actually come from?
4. Why are anaesthetic gases and inhalers a focus for sustainability?
5. Should the NHS be spending money on cutting carbon when waiting lists are this long?
6. You are on work experience and notice a lot of single-use plastic thrown away. What would you do?

Harder questions to stretch you

1. How does climate change affect health in the UK, and who is harmed first?
2. Is it ever right to change a patient’s inhaler for environmental reasons?
3. Reusable instruments sound greener than disposable ones. When might that not be true?
4. If the NHS is only 4 to 5 per cent of UK emissions, and its wider footprint has barely fallen, is any of this worth doing?

Model answer: "Should the NHS be spending money on cutting carbon when waiting lists are this long?"

My honest answer is yes, but not for the reason people expect, because a lot of this work saves money rather than costing it.

The clearest example is desflurane, an anaesthetic gas around 2,500 times more warming than carbon dioxide. The NHS worked with the anaesthetic colleges to stop using it: emissions fell 98 per cent and it saves up to £4 million a year. Fixing nitrous oxide leaks saved another £2.3 million. Nobody waited longer for an operation because of either.

I would not pretend it is all free. The expensive part is the estate, heat decarbonisation in particular, where the capital funding the NHS has relied on is running out. That money does compete with beds and staff.

What settles it for me is that this is not really environment against patients. Air pollution and heat make people ill now, and the biggest source of NHS emissions is the supply chain, where the lever is procurement rules rather than clinical budgets.

So I would fund the parts that pay for themselves without hesitation, and judge the expensive estate work like any other spending decision. What would change my mind is evidence that a green investment was displacing treatment with no health return.

Why this answer works:

• It refuses the premise politely: the question assumes carbon and care compete, and the answer shows where they do not before conceding where they do.
• It uses two checkable facts: desflurane at 98 per cent and £4 million, nitrous oxide at £2.3 million.
• It concedes the hard part: naming heat decarbonisation shows the candidate read past the good news.
• It takes a position and says what would change it: a view with a condition attached is more useful than a summary with no conclusion.

Answers like this are worth saying out loud rather than reading, which is what our medicine interview tutoring sessions are for.

Key Takeaway: Time this one when you rehearse it, because sustainability answers drift long.

What is the one line to take into the room?

The NHS is about 4 to 5 per cent of the UK’s carbon footprint, and most of that sits in what it buys rather than what it burns, which is why 2045 is a harder target than 2040.

Related topics: the Lord Darzi review for the reform picture, and the NHS Long Term Workforce Plan for staffing.

Key Takeaway: The fastest wins so far, anaesthetic gases and inhaler propellants, worked by changing the product rather than the patient.