Climate and Health
Hidden emissions in everyday inhalers
June 15, 2026
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Metered-dose inhalers use hydrofluoroalkane propellants to deliver medication, contributing to the devices’ carbon footprint.
For millions of Canadians living with asthma or chronic lung disease, inhalers are an ordinary part of daily life. They sit in backpacks, coat pockets, bedside tables, and glove compartments.
Most patients probably never think about the environmental footprint attached to those devices. But metered-dose inhalers (MDIs), one of the most widely prescribed types of inhalers, carry a surprisingly large carbon burden. Research has shown that a single MDI produces emissions equivalent to driving a midsized car 139 kilometres.
Yet despite updated clinical guidance and available lower-carbon options, Ontario physicians are still overwhelmingly prescribing the higher-emission devices.
That’s according to new research led by Queen’s University researcher Anthony Train (Family Medicine, and Scientist in Family Medicine at Providence Care), whose study analyzed more than 750,000 inhaler prescriptions dispensed to Ontarians aged 65 and older between 2017 and 2023.
Published in the journal PLOS ONE, the study found that MDIs continued to account for roughly 70 to 80 per cent of new inhaler prescriptions throughout the study period.
“What we found is we’re not adapting fast enough,” says Dr. Train, an assistant professor in Queen’s Department of Family Medicine. “We’re not realizing the environmental impact of our prescribing despite there being much more awareness out there.”
Tracking prescribing trends through the pandemic
Traditional MDIs rely on hydrofluoroalkane propellants, potent greenhouse gases linked to the devices’ larger carbon footprint. Lower-carbon alternatives such as dry powder inhalers and soft mist inhalers do not require those gases and can reduce emissions substantially.
Dr. Anthony Train brings a family medicine perspective to research on everyday care and clinical decision-making.
Working with Queen’s researcher Angela Coderre-Ball and former medical resident Declan Mulligan, Dr. Train’s team used Ontario health administrative data to track inhaler prescribing patterns before and during the COVID-19 pandemic between April 2017 and March 2023. The study period captured dramatic shifts in healthcare access and respiratory illness trends across the province.
New inhaler prescriptions dropped by 38 per cent during the early months of the pandemic, falling from about 11,700 prescriptions per month before the pandemic to roughly 7,200, something Dr. Train attributes to fewer respiratory infections as a result of public health measures, along with disruptions in access to routine healthcare.
But while prescription rates initially declined, they eventually rebounded toward pre-pandemic levels as healthcare systems stabilized. The rebound also showed that higher-emission inhalers continued to account for the majority of new prescriptions in Ontario despite growing environmental concerns surrounding their use.
“The return to pre-pandemic prescription levels offered an opportunity to see whether prescribing habits had changed,” says Dr. Train. “What we found was that the overall pattern remained remarkably consistent with what we had seen before.”
Ontario’s prescribing trends also differ from several European healthcare systems, particularly in the United Kingdom and Scandinavian countries, where lower-emission inhalers make up a much larger share of prescriptions.
“The findings suggest there is significant room for improvement in Canada,” says Dr. Train. “Many of the countries we compare ourselves to have been more successful in reducing their reliance on metered-dose inhalers, showing that it is possible to shift toward lower-emission alternatives.”
Because healthcare emissions contribute to climate change globally, the types of inhalers being prescribed in Canada are not only a domestic sustainability issue. The continued reliance on high-emission inhalers adds to environmental pressures that are often felt most severely in regions already facing drought, food insecurity, and other climate-related risks despite contributing far less to global emissions overall.
Creating the conditions for change
The persistence of high-emission prescribing reflects a larger challenge in healthcare, where growing awareness and updated guidance do not always translate into changes in day-to-day practice.
“Healthcare providers respond to the systems and incentives around them,” says Dr. Train. “If we want to change prescribing patterns, it has to happen at the policy level.”
That could include changes to drug coverage frameworks, prescribing feedback systems, or other supports that help shift routine decisions across the healthcare system.
“Inhaler prescribing is one of those rare areas where we may be able to reduce emissions without compromising care, but only if we create the conditions that make those choices easier for clinicians and patients.”
