(CNN)Asthma sufferers could sharply reduce their carbon footprint by swapping commonly used inhalers for "greener" alternatives, a study from the University of Cambridge has found.
By swapping metered-dose inhalers for dry powder inhalers, users could reduce their carbon emissions equivalent to reducing their meat consumption or recycling, researchers said Wednesday.
But patients have been warned not to make such changes without medical advice.
Inhalers are used to treat the symptoms of conditions such as asthma by releasing medicine straight into a patient's lungs, widening the airways and making it easier to breathe.
Metered-dose inhalers contain liquified, compressed gas hydrofluoroalkane (HFA) -- a greenhouse gas -- which acts as a propellant to atomize the drug being delivered and to pump it out to the user.
Seven out of 10 of the 50 million inhalers prescribed in England in 2017 were metered-dose inhalers.
Researchers found that these metered-dose inhalers contribute 3.9% of the carbon footprint of the UK's National Health Service (NHS).
Alternative "greener" treatments, such as dry powder inhalers and aqueous mist inhalers, are available, experts said in the study published in BMJ Open.
But the higher up-front price of some dry powder inhalers was a "significant barrier" when moving to such alternatives.
Researchers found that the carbon footprints of metered-dose inhalers were up to 37 times those of dry powder inhalers.
Replacing 10% of metered-dose inhalers in England with the cheapest dry powder equivalents would reduce greenhouse gas emissions by the equivalent of 58 kilotonnes of CO2, the scientists said.
Researchers also found that an individual could save the equivalent of between 150 and 400 kilograms of CO2 a year by using "greener" alternatives -- similar to the effect of reducing meat consumption, recycling, or installing wall insulation.
An estimated 235 million people suffer from asthma worldwide, according to figures from the World Health Organization, and the condition is the most common chronic disease among children.
"Climate change is a huge and present threat to health that will disproportionately impact the poorest and most vulnerable on the planet, including people with pre-existing lung disease," James Smith, a consultant in public health at the University of Cambridge and author of the study, said in a statement.
"Our study shows that switching to inhalers which are better for the environment could help individuals, and the NHS as a whole, reduce their impact on the climate significantly. This is an important step towards creating a zero carbon healthcare system fit for the 21st century," he added.
However, the researchers warned that people with asthma should not stop using their regular medication, but should instead discuss their options with a medical professional.
"It's important to stress that patients shouldn't stop using their usual treatments to reduce their carbon footprint," Alexander Wilkinson, respiratory medicine consultant and author of the study, said.
"Instead we recommend patients review their condition and treatment at least annually with their healthcare professional and at this point discuss whether a more environmentally-friendly inhaler is available and appropriate in their situation."
Experts warned that switching to a different type of inhaler must not come at the expense of asthma sufferers' health.
"We recognize the need to protect the environment, but it's critically important that people with asthma receive the medicines they need to stay well and avoid a life-threatening asthma attack," Jessica Kirby, Head of Health Advice at Asthma UK, said in a statement.
"Switching to a different type of inhaler can be complicated for people with asthma, as it involves learning a new inhaler technique, so it should only be done with support from a GP or asthma nurse," she added.