Study: Metered-Dose Asthma Inhalers Make Up Nearly All Inhaler-Related Emissions

Metered-dose inhalers which contain hydrofluorocarbon propellants—greenhouse gases which trap heat in the atmosphere more powerfully than carbon dioxide—are prescribed for asthma and chronic obstructive pulmonary disease. Because of their impact on the environment, the National Health Service encouraged the switch from propellant-containing metered-dose inhalers to propellant-free alternatives (eg, dry-powder and soft-mist).

The US health care system produces about 550 million metric tons (MMT) of CO₂e emissions annually, compared with England, who produces about 30.4 MMT. Efforts to reduce inhaler-related emissions in the US have been hindered by the limited data on US inhalers’ carbon footprint. Authors of a research letter published in JAMA Network assessed emissions and costs in addition to the estimated total yearly emissions and costs for US brand-name inhalers that are prescribed to Medicare Part D and Medicaid beneficiaries.

For this analysis, all brand-name and generic inhaler prescriptions filled by Medicare Part D and Medicaid beneficiaries in 2022 were included. Emissions that were correlated with the use and disposal of each metered-dose inhaler were calculated with the following formula: inhaler contents (obtained from package insert) × propellant percentage (obtained from McKesson material safety data sheets) × 100-year global warming potential of the propellant (obtained from the Sixth Assessment Report of the Intergovernmental Panel on Climate Change), which represents the earth-warming effect of a gas relative to CO2 during 100 years. Additionally, mean emissions for each inhaler and by inhaler class (metered-dose, dry-powder, and soft-mist) were calculated.

To estimate total emissions in 2022, the investigators took the mean emissions per class and multiplied them by number of claims per class. Further, inhaler claims and costs were extracted from the Centers for Medicare & Medicaid Services (CMS) summary and statistics database.

According to the results, the mean (SD) estimated emissions per inhale by device class were 23.1 (11.3) kg of CO₂e for metered-dose inhalers (n = 14), 0.79 (0.06) kg CO₂e for dry-powder inhalers (n = 19), and 0.78 (0.0) kg CO₂e for soft-mist inhalers (n = 4), in which 10 kg CO₂e equals 41.2 km driven in an average gasoline-powered passenger vehicle. The investigators observed that the inhaled corticosteroid, long-acting β-agonist, metered-dose inhaler mometasone/formoterol (Dulera; Merck) 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 β-agonist, dry-powder inhaler fluticasone/salmeterol (Advair Diskus; GSK; 0.898 kg CO₂e emissions/inhaler, $581.60/Medicare claim).

In addition, short-acting β-agonists were the most prescribed medication category among metered-dose inhalers, with 35.3 million claims. Albuterol sulfate (Ventolin HFA; GSK) had the highest emissions (28.7 kg CO₂e/inhaler) among short-acting β-agonist medications.

The investigators observed a total of 69.8 million CMS inhaler claims in 2022, which resulted in an estimated 1.15 MMT of CO₂e emissions. Metered-dose inhalers made up approximately 70.2% (n = 49.0 million) claims, 98.3% (1.13 MMT) CO₂e emissions, and 37.9% ($7.5 billion) of spending, and dry-powder inhalers accounted for 24.5% (17.1 million) of claims, 1.22% (0.014 MMT) of CO₂e emissions, and 50.8% ($10.0 billion) of spending. Soft-mist inhalers made up about 5.2% (3.6 million) of claims, 0.26% (0.003 MMT) of CO₂e emissions, and 11.3% ($2.2 billion) of spending.

The investigators acknowledge that there are limitations to the study, of which one is the limitations to the CMS-insured population, which do not reflect the overall national inhaler emissions. In addition, manufacturing and active pharmaceutical ingredient emissions were gathered from European studies, and may not carry some uncertainty or be applied to the US. Claims prices also may not represent the out-of-pocket costs that patients with asthma must pay.

REFERENCE

Tirumalasetty J, Miller SA, Prescott HC, et al. Greenhouse Gas Emissions and Costs of Inhaler Devices in the US. JAMA. Published online August 29, 2024. doi:10.1001/jama.2024.15331