Metered-dose inhalers (MDI) occupy a paradoxical place in respiratory health. On the one hand, for more than 50 years they have helped millions of people manage their respiratory conditions – some of which are exacerbated by climate change – and provide relief when symptoms get worse. On the other hand, they are one of the biggest causes of greenhouse gas emissions for healthcare systems. And they are now being targeted for carbon-cutting efforts as health systems strive to reach net zero goals. The culprit is not the inhaled medicine itself. Rather, the emissions come from a greenhouse gas propellant that is currently used in metered-dose inhalers to push the medicine into the user’s airways.
There are inhalers which have already been developed that are propellant-free and have a much lower carbon footprint compared to MDIs, known as dry powder inhalers (DPI). Where clinically appropriate, patients can be prescribed a DPI with the double benefit of maintaining respiratory symptom control and cutting carbon emissions. “We have part of the solution available already,” says Christer Janson, Professor in the Department of Medical Sciences at Uppsala University in Sweden
An existing low-carbon alternative
Janson led a study which found that the mix of MDI and DPI use varies enormously between countries, suggesting that some countries could increase the proportion of patients using DPIs, instead of MDIs, without compromising on patient care. According to a report by NHS England, if 30 per cent of patients changed to non-propellant inhalers and achieved equivalent or better health outcomes, almost half of the carbon footprint of MDIs would be eliminated.
In some countries, physicians are encouraged to discuss these kinds of changes with patients. “We always want to empower patients to take responsibility for their own treatment,” says Janson. “At the same time, we don’t want to green-shame them into feeling they are doing something that’s bad for the environment. The important thing is that they treat their respiratory conditions in the best way.”
The Global Initiative for Asthma (GINA) recommends that physicians first consider the best medicine and inhaler type to achieve the best symptom control for a given individual. If that yields a choice of inhaler, they and the patient should then consider environmental impact. GINA notes that good asthma control, regardless of inhaler type, is associated with lower carbon emissions because it reduces reliance on the carbon-intensive activities that come with hospitalisation and emergency healthcare. Janson points out that, in many cases, symptom control and emission reductions go hand in hand.
Towards sustainable MDIs
Although increasing the proportion of DPIs could make a big dent in carbon emissions from inhaler use, MDIs cannot be eliminated completely. Some patients, such as children, the elderly or those with low inspiratory capacity, need the propellant to deliver the correct dose of medicine to their airways. Some patients also feel more secure using an MDI during asthma attacks or other exacerbations. For these patients, a number of manufacturers are reformulating their MDIs. Among them is GSK, which has been testing a low-carbon technology for the past two years that, if successful, could reduce the carbon emissions of their MDI by approximately 90 per cent.
Developing a low-carbon MDI is a complex process, says Laura Clow, Medicine Development Leader at GSK. In addition to reducing carbon emissions, it must be suitable for patients to take, it must be stable, and it needs to have a shelf life that is long enough to make it practical for patient use. “A lot of early development in the chemistry and formulation space looked at all of those things,” she says. Now, GSK is going ahead with several clinical trials to test whether an inhaler using its chosen low-carbon technology performs as well for patients as existing inhalers.
A major part of the challenge, says Clow, is that developing low-carbon MDIs is uncharted territory. “Without having set regulatory pathways to develop low-carbon medicines, it makes it very challenging,” she says.
As part of goals to reduce its impact on the environment and nature, GSK has pledged that its carbon emissions in 2030 will be 80 per cent lower than they were in 2020 and net zero by 2045. “Delivery of low-carbon MDIs is critical for that,” says Clow, noting that MDIs are responsible for around half of the company’s total emissions.
Lower-carbon inhalers will also be key for the 75 health systems that have so far committed to lowering their carbon footprint, with 30 of those setting targets for net zero emissions by 2050 or earlier. The NHS England report on delivering net zero says that a transition to lower-carbon MDIs, after increasing DPI use, would eliminate most of the remainder of the emissions from inhalers.
Governments can take action now to encourage the use of propellant-free DPI inhalers where appropriate. And, with low-carbon propellant inhalers on their way to being available by the second half of this decade, should clinical trials and regulatory processes be successful, governments should consider preparing the ground for a swift and smooth transition that helps both people and the planet.
