Modelling the climate impact of inhalers and mitigation strategies: a population-based study in British Columbia, Canada (2015-2032).

BACKGROUND: Canada has one of the highest per capita greenhouse gas (GHG) emissions, with healthcare contributing ~5% of the total. Pressurised metered-dose inhalers (pMDIs) are significant contributors due to their use of hydrofluorocarbon propellants. While propellant-free dry powder inhalers (DPIs) and soft mist inhalers (SMIs) are available, their adoption remains limited. This population-based study evaluates inhaler dispensation trends in British Columbia (BC), Canada, projects future dispensation and emissions over the next decade, and explores mitigation strategies through pMDI substitution. METHODS: Historical inhaler dispensation data (2015-2022) from BC were analysed using negative binomial models to assess trends, project future usage and emissions (2023-2032) and evaluate four substitution scenarios replacing pMDIs with low-GHG alternatives or DPIs/SMIs. Emissions were estimated by inhaler type, sex, age and health region, with uncertainties addressed through Monte Carlo simulation for the projected values. RESULTS: An average of 2.1 million inhalers are dispensed annually in BC, with pMDIs comprising 64% of total inhaler use but contributing 98% of the ~30 000 tonnes of GHG emissions. There was regional variation and older populations contributed disproportionately, reflecting burden of disease. From 2015 to 2022 (excluding 2020 and 2021, the COVID-19 years), pMDI dispensations decreased by 1% annually while DPI/SMI dispensations increased by 5%. Projections show that, without intervention, emissions could rise to ~37 000 tonnes by 2032, varying by age group. All substitution scenarios, by replacing pMDIs with DPIs/SMIs, could reduce emissions by up to 42%. CONCLUSION: High quality, guideline-directed diagnosis and management of respiratory disease is known to improve health and reduce emissions. Building on these benefits, our analysis shows that substituting pMDIs with lower-emission inhalers, when guided by policy and clinical decisions that prioritise patient safety and preference, can significantly reduce healthcare-related GHG emissions.