Greenhouse gas emissions from inhalers used to treat asthma and COPD in the United States rose by 24% between 2014 and 2024, according to the largest analysis of its kind—raising a new kind of dilemma for clinicians who now must consider not only symptom control and cost but also the climate impact of their prescriptions.1
“Some inhalers are indeed better for the environment than others, and clinical guidelines are largely agnostic on which inhalers in a given therapeutic class are prescribed,” said the study’s first author William B. Feldman, MD, PhD, MPH, a pulmonary critical care specialist at the University of California, Los Angeles.
In the study, published in the Journal of the American Medical Association, researchers used methods based on prior studies to aggregate dispensing records in the Symphony Health Metys database to estimate emissions for all inhalers approved for asthma or COPD. The goal was to quantify the magnitude, sources, and social costs of inhaler-related emissions in the United States from 2014 to 2024. Outcomes included inhaler use and emissions expressed as carbon dioxide equivalents (CO2e).
“One of the strengths is that we analyze emissions at the National Drug Code (NDC) level, meaning that we analyze different strengths of the same drug, which can be associated with different emissions,” Dr. Feldman said. “This enables slightly more precision than prior analyses.”
The cohort included 57 brand-name inhalers approved for asthma or COPD across 11 therapeutic classes. The researchers found that 1.6 billion inhalers were dispensed in the United States between 2014 and 2024, resulting in approximately 24.9 million metric tons of CO₂e (mtCO₂e). During this period, annual emissions rose by 24%, increasing from 1.9 million mtCO₂e in 2014 to 2.3 million mtCO₂e in 2024.
Metered-dose inhalers accounted for 98% of emissions, with most emissions originating from short-acting β-agonist, inhaled corticosteroid-long-acting β-agonist, and inhaled corticosteroid categories. Albuterol, budesonide-formoterol, and fluticasone propionate inhalers made up 87% of total emissions. Of these, 28% came from generic or authorized generic products. The social costs linked of these emissions were estimated at $5.7 billion, with a lower bound of $3.5 billion and an upper bound of $10.0 billion.
According to Dr. Feldman, part of the emissions increase observed during the study period may stem from US population growth and from a higher number of patients with asthma and COPD, even if disease rates are unchanged.
“Some of the increase could also owe to changing prescribing patterns, including more off-label use, but our data do not speak to this,” he said.
Dr. Feldman added that guidelines in COPD recommending LAMA-LABA (long-acting muscarinic antagonist-long-acting β2-agonist) combination therapy, for example, do not distinguish between which LAMA-LABA should be prescribed (dry powder, soft mist, or metered-dose).
“Yet dry powder and soft mist inhalers are associated with far lower emission than metered-dose inhalers,” Dr. Feldman said. “Patients and clinicians can opt for dry powder and soft mist inhalers when available and clinically appropriate. However, we must remember that prescribing is often dictated by formulary design, and so dry powder and soft mist inhalers could be more expensive for patients in some cases.”
He acknowledged certain limitations of the study, including the absence of data on prescriptions within the US Veterans Affairs system or those covered by other military payers, so the study may therefore slightly underestimate or overestimate total national emissions.
Mark A. Malesker, PharmD, FCCP, Professor of Pharmacy Practice and Medicine at Creighton University, Omaha, Nebraska, who was not affiliated with the study, said he was impressed by the comprehensive nature of the work.
“While this study does raise concerns about polluting emissions from inhalers, many manufacturers are already working on propellants with newer formulations that have a lower global warming potential,” he said.
He also underscored the importance of speaking with a health care provider before making any changes to prescribed inhaler use.
“It may be possible for some patients to go on an alternate agent if they’re so inclined or if their provider is so inclined to work toward that goal,” Dr. Malesker said. “However, there are logical challenges that have to be put into play to eliminate any gap in communication and inhalation during a transition period to a new medicine—such as patient-specific inhaler technique instructions—sort of resetting the patient on their new medicine.”
Most importantly, Dr. Feldman said, clinicians must ensure patients have the therapies they need at affordable prices that, ideally, impose minimal amounts of environmental harm. In practice, that may mean favoring dry-powder or soft-mist inhalers when they are clinically appropriate and financially accessible, while advocating for greener propellants and more environmentally conscious formularies.
References
1. Feldman WB, Han J, Raymakers AJN, et al. Inhaler-related greenhouse gas emissions in the US: a serial cross-sectional analysis. JAMA. 2025;334(18):1638-1649. doi:10.1001/jama.2025.16524
