Study Shows Patients Can Slash Their Carbon Footprint With “Green” Inhalers

asthma inhaler and refill
Researchers investigated how a switch from metered-dose inhalers to dry powder inhalers might affect greenhouse gas emissions and drug costs.

Patients with asthma and related conditions can reduce their carbon footprint by replacing metered-dose inhalers (MDIs) with dry powder inhalers (DPIs), according to a study in BMJ Open.1

MDIs contain hydrofluoroalkane (HFA), or liquefied, compressed gases that serve as a propellant to atomize and deliver the medicine to the patient.2 HFAs are potent greenhouse gases: Currently MDIs contribute nearly 4% of the carbon footprint of the National Health Service (NHS) in the United Kingdom. Approximately 7 in 10 inhaler prescriptions in the United Kingdom are MDIs.3

Examining the Environmental and Financial Costs of Inhalers

Researchers at the University of Cambridge set out to determine how a switch from MDIs to DPIs might affect greenhouse gas emissions and drug costs. To do so, they collected carbon footprint data on commonly used inhalers and examined NHS prescription data in the United Kingdom from 2017.1

Information on the amount of HFA propellant in MDIs was not publicly available, so the investigators reviewed scientific publications, independently certified reports, and patents to estimate the contents of the inhalers. They calculated carbon footprint by multiplying the estimated weight of HFA by its global warming potential (GWP).

Inhalers were separated into categories such as short-acting beta-agonists and inhaled corticosteroids. Within each category, the researchers identified high and low GWP inhalers and calculated the carbon impact and cost of switching from high to low GWP inhalers. They modeled scenarios for switching inhalers using current market share of each equivalent DPI and switching to the most affordable pharmaceutically equivalent DPI.

A Greener Alternative

The investigators found that MDIs had a carbon footprint 10 to 37 times that of DPIs. At 2017 prescription levels, swapping 1 in 10 MDIs for DPIs would reduce carbon emissions by 58 kilotons of CO2. At the individual level, each MDI replaced by a DPI would result in 150 kg to 400 kg of CO2 reduced annually, which is the equivalent of recycling or cutting meat out of a diet.1

Replacing 10% of MDIs with the cheapest available DPIs would reduce the total cost by £8.2 million per year. However, replacing 1 in 10 MDIs with DPI brands following prescribing patterns observed in 2017 would increase drug costs by £12.7 million annually.

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The researchers suspect that upfront cost might be a significant barrier to switching from MDIs to DPIs. However, they noted, “the price of MDIs does not take into account the long-term financial cost of their environmental impact.”


The investigators called climate change a “huge and present threat to health” and stressed that every effort must be made to reduce greenhouse gas emissions. Switching from MDIs to DPIs would yield large carbon savings, a feat that can be achieved alongside reduced drug costs by using less expensive brands.1

“Our study shows that switching to inhalers which are better for the environment could help individuals, and the NHS as a whole, reduce their impact on the climate significantly,” they concluded. “This is an important step towards creating a zero carbon healthcare system fit for the 21st century.”2


  1. Wilkinson AJK, Braggins R, Steinbach I, Smith J. Costs of switching to low global warming potential inhalers. An economic and carbon footprint analysis of NHS prescription data in England. BMJ Open. 2019;9(10):e028763. 
  2. Brierley C. Switching to ‘green’ inhalers could reduce carbon emissions and cut costs, study suggests. University of Cambridge. October 30, 2019. Accessed November 4, 2019.
  3. UK progress on reducing F-gas emissions. House of Commons Environmental Audit Committee. April 25, 2018. Accessed November 5, 2019.