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Inhalers prescribed to Centers for Medicare & Medicaid Services (CMS) beneficiaries for asthma and chronic obstructive pulmonary disease resulted in estimated emissions of greenhouse gases equivalent to 226,960 homes' yearly electricity use, researchers said.

More specifically, 69.8 million CMS inhaler claims in 2022 led to an estimated 1.15 million metric tons (MMT) of carbon dioxide equivalent emissions (CO₂e), reported Jyothi Tirumalasetty, MD, of Stanford University School of Medicine in California, and colleagues in .

Metered-dose inhalers accounted for 49 million claims and nearly all of those emissions, at 1.13 MMT CO₂e (98.3%), as well as $7.5 billion of spending.

Alternatives to metered-dose inhalers -- dry-powder inhalers and soft-mist inhalers -- were responsible for substantially fewer emissions (0.014 and 0.003 MMT CO₂e, respectively), but they were disproportionately costly, representing around one-third of inhaler claims but nearly two-thirds of the costs, at $10 billion for dry-powder inhalers and $2.2 billion for soft-mist inhalers.

"We were surprised that there was a great deal more being spent on dry-powder inhalers despite that fact that they were prescribed less," Tirumalasetty told MedPage Today.

She noted that Canada and the U.K. have implemented programs to encourage the switch to more environmentally friendly inhalers. Meanwhile, the U.S. healthcare system produces around 18 times the carbon dioxide equivalent emissions that the U.K.'s National Health Service does, "yet efforts to reduce inhaler-related emissions in the U.S. have been hindered by limited data on the carbon footprint of U.S. inhalers," the authors wrote.

Metered-dose inhalers contain hydrofluorocarbon propellants, usually liquefied gas, mixed with medication in a canister that patients dispense in an aerosolized burst for a specific quantity of the medicine. According to Tirumalasetty, the majority of hydrofluorocarbons -- greenhouse gases that trap heat in the environment -- are released when patients exhale. A portion of the propellant remains in the canister and is then released during disposal, where it slowly leaks into the atmosphere.

Dry-powder inhalers allow a measured dose of powder to be inhaled using the force of a patient's inhalation without propellants, and soft-mist inhalers use energy from a spring to spray liquid out of nozzles to be inhaled in a mist. Tirumalasetty said that the emissions from these two kinds of inhalers are mostly attributed to manufacturing or active pharmaceutical ingredient emissions.

Mean estimated emissions per inhaler for each type were 23.1 kg CO₂e for metered-dose inhalers, 0.79 kg CO₂e for dry-powder inhalers, and 0.78 kg CO₂e for soft-mist inhalers. For comparison, 10 kg CO₂e is equivalent to driving about 26 miles in an average gas-powered car.

"This study highlights the magnitude of inhaler-related emissions in the U.S., as well as potential cost barriers to propellant-free inhaler substitutions," Tirumalasetty and colleagues wrote. "Formulary choices that optimize clinical efficacy, greenhouse gas emissions, and affordability may improve patient outcomes and reduce climate pollution."

Some HHS should encourage the development of affordable dry-powder inhalers, and insurers and hospitals could create a bigger demand for them. Reducing health disparities that increase the burden of asthma-related complications and deaths for Black and Native American people could also lead to more effective asthma control, thereby reducing inhalers' carbon footprint.

For this study, the researchers used all brand-name and generic inhaler prescriptions filled by Medicare Part D and Medicaid beneficiaries in 2022, with claims and costs from the CMS summary and statistics database.

They calculated emissions per inhaler using the weight of the inhaler listed on the package insert, the propellant percentage, and the 100-year global warming potential of the propellant. Percentage and type of propellant were detailed in , and the global warming potential represents the earth-warming effect of a gas relative to CO₂ over 100 years from the of the Intergovernmental Panel on Climate Change.

Mometasone/formoterol (Dulera), the inhaled corticosteroid, long-acting beta-agonist, metered-dose inhaler, had the highest emissions per inhaler, at 48.1 kg CO₂e, and cost $444.37 per Medicare claim compared with the analogous inhaled corticosteroid, long-acting beta-agonist, dry-powder inhaler fluticasone/salmeterol (Advair Diskus), which had 0.898 kg CO₂e emissions per inhaler and cost $581.60 per Medicare claim.

Among metered-dose inhalers, short-acting beta-agonists were the most prescribed medication category, with 35.3 million claims. Of these medications, albuterol sulfate (Ventolin HFA) had the highest emissions, at 28.7 kg CO₂e per inhaler.

Study limitations included that estimates of emissions were only from the CMS-insured population, and did not reflect total national inhaler emissions. In addition, emissions from manufacturing and active ingredients were estimated based on European studies, and claims prices may not have included out-of-pocket expenses.

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