Review Examines Environmental Impact of Inhaler Choice in the UK

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Switching patients from pressurized metered dose inhalers (pMDIs) to dry powder inhalers (DPIs) could both reduce health care system’s carbon footprint and result in more satisfied patients.

Authors of a recent review suggested that dry powder inhalers (DPIs) should be considered first for patients with chronic obstructive pulmonary disease (COPD) and asthma compared with pressurized metered dose inhalers (pMDIs) because of the environmental benefits, as DPIs do not require propellant.

In the United Kingdom, 3.5% of the National Health Services’ (NHS) carbon footprint is derived from pMDIs, said the authors, from Brighton & Sussex University Hospitals and Brighton & Sussex Medical School, in Brighton.

“While pMDIs contribute only a small proportion of the carbon footprint of the NHS, if this can be reduced with no negative impacts on patients then we would argue that this should be prioritized along with other measures taken to make healthcare more sustainable,” wrote the authors.

The hydrofluoroalkane (HFA) propellants used in pMDIs is responsible for 96% of the global warming potential for pMDIs and can be up to 3800 times a more powerful greenhouse gas than carbon dioxide.

The authors noted a prior study calculated that if the United Kingdom replaced 10% of pMDIs with DPI devices, more than 68.8 kilo tonnes of carbon dioxide, equivalent to the mass generated from 43,000 roundtrip transatlantic flights, could be saved annually.

In addition, the environmental impact also stems from improper disposal, whether there are doses that are left in the canisters or not. Not all pMDIs have dose counters built in, and some may be tossed with additional usage left in them. These continue to release gas, the review noted. The authors cited a study where pMDIs that were disposed of improperly from 1 hospital over 90 days were collected; the disposed canisters would have produced an equivalent of 2.63 tonnes of carbon dioxide emissions being released into the atmosphere if they were ended up in a landfill.

In addition to the environmental benefits of DPIs, the authors said that DPIs tend to be easier to use than pMDIs as they use a propellant-free mechanism that relies on the patient’s lung and muscle capabilities to pull the drug into the lungs themselves.

This ease of use translates into optimum inhaler technique for the patient. While there is no significant difference in the efficacy of different inhaler types when used properly, coordination between actuation of the inhaler and slowly inhaling the drug by the patient can be a challenge for patients who use pMDIs.


One study cited by the authors found that patients used the correct technique for pMDIs only 23% of the time compared with DPIs (43%). Another study found that the correct technique was used for pMDIs 53% of the time compared with DPIs (59%).

“DPIs are not an appropriate choice of inhaler for patients who are not able to generate sufficient inspiratory flow.”

In many cases, patients with COPD or asthma are eligible for either inhaler type, with pMDIs tending to be cheaper than DPIs on a per-inhaler basis.

However, the authors said that, overall, DPIs have a greater cost benefit because costs could be offset by the savings from other inhaled medications, citing 1 study that found that replacing 10% of pMDIs with DPIs would result in £8.24 million (US$9.72 million) in annual savings.

Some studies have found that patients with COPD and asthma preferred to use DPIs as opposed to pMDIs, they said. A study from 2011 found that a majority of patients chose to keep using a DPI after switching from a pMDI 3 months prior.

The authors noted that hydrofluorocarbon propellants, such as HFAs, are used in other industries, including air conditioning and refrigeration, where regulation is beginning to be implemented across sectors and, therefore, “healthcare should not be exempt from being required to take action.”


Starup-Hansen J, Dunne H, Sadler J, Jones A, Okorie M. Climate change in healthcare: Exploring the potential role of inhaler prescribing. Pharmacol Res Perspect. 2020;8(6):e00675. doi:10.1002/prp2.675