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 is the hot topic where the gap between a rehearsed answer and a thought-through one is widest, because almost everyone reaches for recycling and almost nobody knows where the emissions actually are. Our medicine interview hot topics guide covers the wider current-affairs picture; this page is the one topic in detail.

Why the NHS is part of the climate problem, not a bystander

At Hull Women and Children’s Hospital, staff worked out that 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. They started keeping the valves disconnected until the gas was needed. Monthly emissions fell from 395 tonnes of carbon dioxide equivalent to 43, and £3,000 a month stopped being wasted. Patients used exactly as much pain relief as before.

That is the reframe this topic turns on. Healthcare is not a bystander to climate change, it is a contributor. The NHS is responsible for around 4 to 5 per cent of the country’s carbon footprint and roughly 30 to 40 per cent of all public sector emissions. Treating illness produces emissions that go on to cause illness, an uncomfortable loop for a service whose first duty is to do no harm. In October 2020 it became the world’s first national health system to commit to net zero, and more than 40 other health systems have since followed.

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

The two net zero targets, and the one people get wrong

The NHS has two net zero dates, not one. The 2040 target covers the emissions it controls directly. The 2045 target covers the far larger footprint it can only influence, and that is the harder of the two by a wide margin.

Both run from a 1990 baseline, and progress is uneven. Direct emissions are down 68 per cent since then and 14 per cent since 2019/20, but the wider footprint is broadly where it was in 2019. That looks like failure until you measure it per unit of work: it has fallen 15 per cent per real pound of NHS budget and 7 per cent per hospital admission. The NHS is doing more at a lower carbon cost each time, which is not the same as emitting less.

One caveat. Greener NHS sits inside NHS England, which is itself being abolished and folded into the Department of Health and Social Care. The targets belong to the NHS rather than to one organisation and are expected to survive, but where the programme is run from is in flux. The wider map of how the NHS is organised is a separate topic.

Key Takeaway: Say both dates, 2040 and 2045, and say what separates them. Most candidates only know one.

Where the emissions come from, and why procurement beats lightbulbs

Most of the NHS footprint is not hospitals. It is the things hospitals buy. The table below is most of what you need, and the first row is the one that changes an answer.

Two rows surprise people. Buildings and energy, where every intuition points, are about a tenth of the total. And personal travel, roughly 90 per cent of it by car, is several times the entire NHS vehicle fleet, which is one reason telemedicine and artificial intelligence in the NHS are sustainability questions and not only safety ones.

The supply chain row is the point. The NHS buys over 600,000 products from around 80,000 suppliers, so its real lever is not switching off lights, it is being an enormous customer that can 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, so a supplier ignoring carbon loses marks.
• Carbon reduction plans are mandatory. Required from April 2023 for contracts above £5 million a year and for all new procurements from April 2024, covering around 90 per cent of NHS non-pay spend.
• Single use is being designed out. The Design for Life roadmap commits the NHS to a circular system for medical technology by 2045.

A cost argument sits underneath it: every pound spent decarbonising is a pound not spent on treatment, the same allocation problem QALYs exist to referee, and it competes with winter pressures for the same capital.

Key Takeaway: If you remember one thing, remember that the supply chain is close to half the footprint, so procurement is the lever.

The clinical quick wins: anaesthetic gases and inhalers

Anaesthetic gases and inhaler propellants are only about 3 per cent of the footprint, but they have delivered the fastest cuts the NHS has managed, because a clinician can change them this week without rebuilding anything. They are the same idea twice: a tiny volume of gas with an enormous warming effect per kilogram.

• Desflurane. Roughly 2,500 times more warming than carbon dioxide. NHS England worked with the Royal College of Anaesthetists and the Association of Anaesthetists to decommission it in favour of clinically appropriate alternatives, committed in January 2023 and completed through 2024. Emissions are down 41 kilotonnes, a 98 per cent cut, 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. Better supply management has saved over £2.3 million a year and around 90 kilotonnes since 2019/20.
• 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 over 340 kilotonnes, or 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 next-generation propellant HFA-152a. Same drug, same doses, in the UK later in 2026, and propellants of this type should cut a metered dose inhaler’s footprint by at least 90 per cent.

Together, medicines emissions are down 470 kilotonnes, 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. Better care and lower emissions are the same intervention more often than you would think.

Key Takeaway: One dated example beats a general point. Desflurane, 98 per cent down and £4 million a year saved, is the most quotable fact here.

Climate change as a health threat multiplier

Climate change mostly does not create new diseases. It makes existing ones more common, more severe and more unequally spread, which is why doctors call it a threat multiplier. In the UK it lands in three places.

• Heat. The UK Health Security Agency estimated 1,504 heat-associated deaths in England in summer 2025, after a record 2,985 in 2022, the year the UK first passed 40 degrees. Death rates are highest by far in people aged 85 and over, and NHS England puts the cost of heat-related mortality at around £6.8 billion a year in the 2020s, rising towards £14.7 billion by the 2050s.
• Air quality. The fossil fuel use that warms the climate also degrades the air, driving asthma, lung disease and heart disease. This is the clearest co-benefit: cutting emissions improves health now, not only in fifty years.
• Infection and extreme weather. Warmer conditions widen the range in which diseases such as dengue and yellow fever spread, and severe weather disrupts NHS care at exactly the moment demand rises.

None of it lands evenly. Poor housing, a flat that overheats and a main road outside cluster in the same places, so the burden falls on people already at the wrong end of the social gradient set out in the Marmot Review of health inequalities. Linking climate to inequality turns a factual answer into a persuasive one.

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

Where sustainability and patient care genuinely pull against each other

Every quick win above has a version that harms a patient, and knowing which is which is the difference between an argument and a slogan. This is the part worth the most preparation, because interviewers push here.

• Desflurane was not banned for being a bad drug. It wakes patients up faster than the alternatives, which some anaesthetists valued. It went because safe, effective, cheaper alternatives existed, and exceptional clinical use is still permitted. "Ban the worst gas" only works when something as good replaces it.
• "Ban nitrous oxide" takes 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 that decommissioned leaking manifolds kept it available through cylinders attached directly 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, and they cannot be used with a spacer. Guidance is explicit that devices should not be changed without consulting the patient. The greenest inhaler is the one the patient will actually use properly, which is why changing the propellant matters more than changing the device.
• 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 and how clean the electricity is. Infection control sets hard limits too.

The case: in 2001 the Department of Health required single-use instruments for tonsil surgery in England, because of a theoretical risk of transmitting variant CJD through instruments ordinary sterilisation does not decontaminate. Surgeons then reported more bleeding after surgery, linked to the disposable diathermy forceps, and the requirement was withdrawn. Infection control and environmental impact do not always point the same way.

The pattern for holding two goods in tension is in our guide to answering medical ethics interview questions: name the benefit, name the patient who loses, then say what evidence would move you.

Key Takeaway: Never argue for a green change without naming the patient it could harm. That is the sentence interviewers are waiting for.

What you can honestly say you have done

Keep this small and true. Nothing a sixth-former does moves 27 megatonnes, and a panel can tell when a claim has been inflated.

• Notice something real on placement. How much packaging comes off one sterile pack, or how many people drove to a clinic that could have been a phone call.
• Read one Green Plan. Every NHS trust publishes one. Naming your local trust’s plan and one thing in it takes twenty minutes and is checkable. Sustainable healthcare also makes an unusually good EPQ subject.
• Link it to prevention. The lowest carbon consultation is the one that never has to happen, which is why the sugar tax and the response to the obesity crisis have a climate dimension too.

When I run mock interviews, the best answer I have heard came from a candidate who had asked her GP why the practice had changed inhaler brands. She could describe the conversation, including the patient who refused to switch. That was worth more than any statistic she could have memorised.

Key Takeaway: One honest, specific observation from your own experience will outperform a list of national targets.

What interview questions could come up on the greener NHS

Likely questions

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 what proportion of the UK’s carbon footprint does it produce?
3. Where do most NHS emissions actually come from?
4. Why are anaesthetic gases and inhalers a focus for sustainability in healthcare?
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?

Less likely questions (harder, but worth knowing)

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 in five years, 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 refused the premise politely. The question assumes carbon and care compete. It showed where they do not before conceding where they do.
• It used two dated, checkable facts. Desflurane at 98 per cent and £4 million, nitrous oxide at £2.3 million. Numbers do more work than enthusiasm.
• It conceded the hard part. Naming heat decarbonisation and the end of the capital funding shows the candidate read past the good news.
• It took a position and said what would change it. A view with a stated condition attached sounds more considered than a balanced summary with no conclusion.

The wider reform picture is in the Lord Darzi review and the staffing picture in the NHS Long Term Workforce Plan. To practise answers like this out loud, our medicine interview tutoring runs mock MMI and panel interviews with personalised feedback.

Key Takeaway: Rehearse this one out loud and time it, because sustainability answers drift long and a panel stops listening at ninety seconds.

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