Inhalers are the front-line treatment for asthma and COPD, but they come with a steep environmental cost, according to a new UCLA Health study - the largest to date quantifying inhaler-related emissions in the United States.

Researchers found that inhalers have generated over 2 million metric tons of carbon emissions annually over the past decade, equivalent to the emissions of roughly 530,000 gas-powered cars on the road each year.

The study, published in JAMA, analyzed emissions from the three types of inhalers approved for asthma or COPD from 2014 to 2024. It found that metered-dose inhalers were the most harmful to the environment, accounting for 98% of emissions over the 10-year period. Metered-dose inhalers contain hydrofluoroalkane propellants, which are potent greenhouse gases that were widely used in products such as aerosol sprays. The other types of inhalers, which include dry inhalers and soft powder mist inhalers, are less harmful to the environment as they deliver medication to the lungs without the need for propellants.

"Inhalers add to the growing carbon footprint of the U.S. health care system, putting many patients with chronic respiratory disease at risk," said Dr. William Feldman, a pulmonologist and health services researcher at the David Geffen School of Medicine at UCLA and the study's lead author. "On the upside, there is tremendous opportunity to make changes that protect both patients and the planet by utilizing lower-emission alternatives."

Researchers conducted the study using a comprehensive U.S. database capturing inhaler prescriptions at the National Drug Code level. Emissions were then estimated using validated academic studies and analyzed by drug type, device type, propellant type, therapeutic class, branded status, manufacturer, payer and pharmacy benefit manager.

Researchers plan to expand their research to examine inhaler-related emissions in specific patient populations, such as those on Medicaid. They will also compare clinical outcomes between lower-emission and higher-emission inhalers in the same therapeutic class and explore pricing and patenting strategies that pharmaceutical companies may use as they roll out lower-emission inhaler technologies.

"A key first step to driving change is understanding the true scale of the problem," Feldman said. "From there, we can identify what's fueling these emissions and develop targeted strategies to reduce them-benefiting both patients and the environment."