Metered-dose inhalers and their impact on climate change

Pressurized metered dose inhalers (pMDIs) contribute significantly to greenhouse gas emissions

The hydrofluorocarbon propellants in pMDIs are responsible for approximately 0.03% of annual global greenhouse gas emissions.1 Prescriptions of pMDIs account for approximately 3% of total UK National Health Service healthcare related emissions. Uni.2 The carbon footprint of one pMDI (200 doses) is estimated to be the equivalent of a 290 km car journey.3 Reducing pMDI prescriptions, if any, could have a significant impact on the ‘environment.

Alternative low carbon impact inhalers are available

Dry powder and soft-mist inhalers, both available as quick-relief and maintenance therapies, are commonly used in the treatment of asthma and chronic obstructive pulmonary disease. Dry powder and soft mist inhalers contribute to a lower carbon dioxide equivalency (2e by inhalation) than pMDI (about 100 g CO2e by inhalation).1

Dry powder and soft mist inhalers are effective and may have advantages over prescription pMDI

Compared to pMDIs, alternative inhalers show similar efficacy and are often preferred by patients.46 Canadian Thoracic Society guidelines emphasize that rescue therapy with a budesonide-formoterol dry powder inhaler is an appropriate alternative to short-acting pMDI β-agonists in some patients with asthma, including including those with milder disease7. advice on the pros and cons of various inhalers, including their impact on climate change. Resources for implementing changes to inhaler prescriptions (i.e. posters, electronic medical record tools, patient letters), cost comparison charts, and selection criteria patient information are accessible to the public.3

Prescribing only medically indicated inhaler therapy could significantly reduce carbon emissions

One-third of patients labeled as asthmatic do not have asthma on objective tests.8 In the absence of a confirmed diagnosis, avoiding unnecessary prescription of inhalers could significantly reduce health system emissions.

Proper recycling and disposal of inhalers can reduce carbon dioxide emissions

Recycling inhalers in pharmacies, as opposed to landfilling, enables the reuse of plastic or aluminum components and reduces CO2 production.3


  • Competing interests: Lee Fidler reports receiving grants from the Canadian Pulmonary Fibrosis Foundation, the University of Toronto, and the Sunnybrook Hospital Academic Funding Plan. Samantha Green is a board member of the Canadian Association of Physicians for the Environment (volunteer position). Kimberly Wintemute reports receiving salary support from Choosing Wisely Canada (2015-2021), consultation fees from Manitoba Justice, Crown Attorney’s Office (2021), fees from Safer-MedsNL for a presentation and payment for a expert testimony for the Crown Attorney’s Office. Crown Attorney, Halton Region, Ontario.

  • This article has been peer reviewed.

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The references

  1. Montreal Protocol on Substances that Deplete the Ozone Layer: UNEP Medical Care Technical Options Committee Report 2014. Nairobi [Kenya]: United Nations Environment Program; 2015.