What the research shows

Inhalers are a lifeline for millions of Americans living with asthma and other chronic lung diseases, but they come with a hidden cost. The same propellants that help patients breathe easier also release planet-warming gasses that are thousands of times stronger than carbon dioxide (CO2).

Over the past decade, researchers have found that U.S. inhalers produced 24.9 million metric tons of CO2-equivalent emissions — about the same as half a million cars or the electricity use of 470,000 homes each year.

For the first study, William Feldman and colleagues at the University of California, Los Angeles (UCLA) and Brigham and Women's Hospital analyzed 1.6 billion inhalers dispensed in the United States from 2014 to 2024 using national pharmacy data.

Feldman and colleagues found that 98% of emissions came from metered-dose inhalers (MDIs), which use hydrofluoroalkane propellants, while dry-powder and soft-mist inhalers produced far less emissions.

Annual emissions rose 24% during the 10-year study period, mostly from common medicines such as albuterol, budesonide-formoterol, and fluticasone propionate, which together made up 87% of total emissions. The researchers estimated the social cost of that pollution at $5.7 billion.

In an editorial published alongside the studies, Alexander Rabin, Jyothi Tirumalasetty, and Stephanie Maximous called inhaler reform one of "the most promising opportunities for the health sector to decarbonize" and said there is "a path to reform that need not compromise care."

Still, switching inhalers isn't a simple move for everyone. Kate Bender of the American Lung Association — who also has asthma — said, "It drives me crazy that the medication I use to address my symptoms drives climate change," and added that "as we get to that future … we need to make sure people still have access to inhalers with propellants and the other options."

Doctors say MDIs remain lifesaving for many patients, especially children who need spacers or older adults who can't inhale powder versions effectively. But experts agree the healthcare system should move toward lower-emission alternatives as more become available.

"It's really on all of us to try to do our part in reducing emissions," Feldman said.