Swapping metered-dose inhalers for dry powder inhalers could reduce the carbon footprint of inhaled medications by 85%, according to new estimates.

Clinicians should work with patients to make the switch now as “there is nothing to be gained by waiting”, the group of UK and Nordic researchers who produced the estimates said.

They used sales and carbon-emission data for propellant-containing pressurised metered-dose inhalers (pMDIs) and propellant-free dry powder inhalers (DPIs) to estimate the overall carbon footprint of their use in the UK and Europe in 2020, as well as the patient-level carbon footprint of different asthma treatment regimes.

Their study, published in BMJ Open, assumed that pMDIs and DPIs had a carbon footprint per dose of 124g and 10g of carbon dioxide equivalents (CO2e), respectively, where CO2e describes the total global warming potential of greenhouse gases emitted into the atmosphere. 

It found that pMDI use in Europe in 2020 created 3.6 million tons (MT) of CO2e, of which the largest amount – 1.3 MT (44%) – was produced in the UK.

Switching all pMDI inhalers to DPIs in 2020 would have reduced emissions by 85% to 0.28 MT of CO2e in Europe and to 0.11 MT in the UK, the researchers said.

“There is potential to reduce the carbon footprint of inhaled medications by 85% if DPIs are preferred over pMDIs,” they stressed. 

One asthma inhaler greener than two

The researchers also compared the emissions of two different treatment regimens recommended for newly diagnosed asthma patients in the 2021 guidelines of the Global Initiative for Asthma (GINA) (see our story here).

They found that treatment had a substantially lower carbon footprint if a patient with moderate asthma used a single combination inhaler as-needed to deliver an inhaled corticosteroid (ICS) plus a long-acting β2-agonist (LABA), rather than the more traditional maintenance therapy of daily ICS alone plus additional short-acting β2-agonist (SABA) as-needed.

Specifically, assuming 100% adherence to maintenance therapy, they estimated that as-needed budesonide/formoterol DPI (0.52 inhalations/day) produced 0.8kg CO2e per year, compared with the 2.9kg per year associated with the use of twice daily maintenance with budesonide 200ug DPI plus as-needed SABA rescue therapy (0.49 doses per day).

Choose DPI combined inhaler for maintenance and rescue

The researchers noted that 70% of UK patients on inhaled treatment use a pMDI, after the UK switched to pMDIs for inhaled corticosteroids over the last couple of decades, mainly on cost grounds.

Salbutamol accounted for 67% of total pMDI sales in the UK, and around a third of Europe’s pMDI carbon footprint in 2020, they added. 

“A switch to DPI salbutamol would reduce the carbon footprint for salbutamol by >90% but have no impact on asthma control,” they said. “However, a switch to DPI combination LABA/ICS for maintenance and rescue would also reduce the overall carbon footprint by 90%, but in addition, substantially improve asthma control. 

“In terms of greenhouse gas emissions, switching 90% of the current pMDIs in Europe to DPIs would be equivalent to removing 1.5 million cars from the roads. 

“At an individual level, a switch from pMDI to the same medication in a DPI would be similar to changing from a meat to a plant-based diet.”

To read the study, click here