Reducing carbon footprint of inhalers: analysis of climate and clinical implications of different scenarios in five European countries

Background: Inhaled therapies are key components of asthma and chronic obstructive pulmonary disease (COPD) treatments. Although the use of pressurised metered-dose inhalers (pMDIs) accounts for <0.1% of global greenhouse gas emissions, their contribution to global warming has been debated and efforts are underway to reduce the carbon footprint of pMDIs. Our aim was to establish the extent to which different scenarios led to reductions in greenhouse gas emissions associated with inhaler use, and their clinical implications.

Methods: We conducted a series of scenario analyses using asthma and COPD inhaler usage data from 2019 to model carbon dioxide equivalent (CO₂e) emissions reductions over a 10-year period (2020-2030) in the UK, Italy, France, Germany and Spain: switching propellant-driven pMDIs for propellant-free dry-powder inhalers (DPIs)/soft mist inhalers (SMIs); transitioning to low global warming potential (GWP) propellant (hydrofluoroalkane (HFA)-152a) pMDIs; reducing short-acting β₂-agonist (SABA) use; and inhaler recycling.

Results: Transition to low-GWP pMDIs and forced switching to DPI/SMIs (excluding SABA inhalers) would reduce annual CO₂e emissions by 68%-84% and 64%-71%, respectively, but with different clinical implications. Emission reductions would be greatest (82%-89%) with transition of both maintenance and SABA inhalers to low-GWP propellant. Only minimising SABA inhaler use would reduce CO₂e emissions by 17%-48%. Although significant greenhouse gas emission reductions would be achieved with high rates of end-of-life recycling (81%-87% of the inhalers), transition to a low-GWP propellant would still result in greater reductions.

Conclusions: While the absolute contribution of pMDIs to global warming is very small, substantial reductions in the carbon footprint of pMDIs can be achieved with transition to low-GWP propellant (HFA-152a) inhalers. This approach outperforms the substitution of pMDIs with DPI/SMIs while preserving patient access and choice, which are essential for optimising treatment and outcomes. These findings require confirmation in independent studies.