It was great to see Canadian Family Physician publish an article on environmental stewardship (“Climate-conscious inhaler prescribing for family physicians”) in its June 2024 issue.1 The climate-conscious inhaler prescribing sustainable pathway highlighted in the article is a helpful addition to my family medicine practice, and I appreciate the time and effort that went into its development.

I want to comment and expand on step 3 of the pathway: switching from metered-dose inhalers (MDIs) to dry-powder inhalers (DPIs). While switching from MDIs to DPIs will help reduce carbon impact, it is important to realize the actual carbon impact of switching from an MDI to a DPI is not simply a 10-fold reduction as the article suggests, but at best an educated guess. The calculation involves many factors (eg, methodology, type of inhaler, type of propellant) and the data used in such calculations are often estimated, incomplete, or not independently certified.2,3 In addition, the environmental impact of inhalers includes more than the carbon impact; other impacts include fossil fuel and metal depletion, ozone depletion, and ocean acidification. The extent of these factors is still unclear. To my knowledge, the only publication on this showed MDIs (with hydrofluorocarbon-134a propellant, the most common propellant used in Canada) have a lower or similar impact compared with DPIs in 11 of 14 environmental areas. The caveat, though, is the study was funded by a propellant manufacturer.4,5

I also suggest we should strive to present a balanced view. Specifically, the CASCADES (Creating a Sustainable Canadian Health System in a Climate Crisis) poster that appears in the article, “Depending on the type, 1 aerosol inhaler can have the same carbon footprint as driving up to 170 km in a gas car,”1 represents the extreme rather than the average impact. The following statement may be more useful and is calculated using the kilometric equivalent of an average MDI (a 98 kilometre drive): The daily use of an aerosol inhaler is approximately equivalent to a 1 kilometre drive daily while, in comparison, a daily cup of orange juice is equivalent to a 2 kilometre drive daily, and 1 weekly burger is equivalent to a 3 kilometre drive daily.6

Finally, this year I have been at several well-intentioned quality improvement project presentations on switching inhalers based on CASCADES material. The presenters appeared unaware this poster represented an extreme case, that switching inhalers is not a high-yield intervention, and there is uncertainty underlying the actual carbon impact.

It is important for all of us to work together toward an environmentally sustainable future, and the climate-conscious inhaler prescribing sustainable pathway is a welcome step. As CASCADES continues with its much-needed initiatives, I hope it will reconsider its messaging around switching inhalers.

Competing interests

None declared