Comparing the CO2 emissions of metered dose inhalers and dry powder inhalers: a cross-sectional environmental impact analysis of asthma and COPD therapies in South Tyrol, Italy

Abstract

Introduction

Inhalers for asthma and chronic obstructive pulmonary disease (COPD) are essential therapeutic interventions; however, they contribute significantly to healthcare-related CO₂-equivalent (CO₂eq) emissions, particularly currently used metered dose inhalers (MDIs), which use hydrofluoroalkane (HFA) propellants such as HFA-124a and HFA-227. This study quantifies the carbon footprint of inhaler utilisation in South Tyrol, Italy, and evaluates the potential CO₂eq reductions achievable through the transition from MDIs to dry powder inhalers (DPIs).

Methods

This cross-sectional analysis used regional healthcare prescription data for inhalers dispensed in South Tyrol in 2021 and 2022, encompassing approximately 540 000 inhabitants. CO₂eq emissions were calculated based on HFA content in MDIs, employing established global warming potentials, while DPI emissions were estimated from current literature values.

Findings

A total of 100 778 inhalers were dispensed in 2021 (45 031 MDIs, 55 747 DPIs) and 101 334 in 2022 (49 711 MDIs, 51 623 DPIs). MDIs were responsible for approximately 1000–1100 tonnes of CO₂eq annually, whereas DPIs accounted for less than 55 tonnes. A transition to DPIs could potentially result in significant CO₂eq reductions.

Conclusions

Usage of DPIs over currently used MDIs in patients who can use them could mitigate healthcare-associated global warming potential, providing a viable strategy for climate change mitigation in respiratory care. Development of low-global warming potential MDIs is a complementary strategy.

WHAT IS ALREADY KNOWN ON THIS TOPIC.

WHAT THIS STUDY ADDS

• This study provides local evidence from South Tyrol, demonstrating that transitioning from MDIs to DPIs could reduce CO₂eq emissions by several hundred tonnes annually, even in a region with a relatively small population.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The findings support policies aimed at promoting DPIs for stable patients in respiratory therapy to reduce healthcare-related emissions, in parallel to developing greener propellants to suit all patients’ needs. This evidence may inform similar initiatives in other regions seeking to mitigate climate impact within healthcare practices.

Introduction

Chronic obstructive pulmonary disease (COPD) and asthma are among the most prevalent chronic respiratory diseases globally.¹ In South Tyrol, a province in Italy with approximately 540 000 inhabitants, COPD and asthma significantly strain healthcare, with respiratory diseases accounting for 7.4% of all deaths and COPD responsible for 40% of lung disease deaths.²

Metered dose inhalers (MDIs) and dry powder inhalers (DPIs) are the primary treatments for COPD and asthma, crucial for symptom control and improving patients’ quality of life. MDIs, however, rely on hydrofluorocarbons (HFCs) containing hydrofluoroalkane (HFA) propellants HFA-124a and HFA-227, which increase their carbon footprint. Recent studies indicate that switching to DPIs, which do not use HFCs, could reduce CO₂-equivalent (CO₂eq) emissions.³ This study aims to quantify the carbon footprint of inhaler use in South Tyrol and examine the environmental benefits of transitioning from currently used MDIs to DPIs.

Methods

The investigation quantified the carbon footprint of inhalers prescribed for asthma and COPD in South Tyrol during 2021 and 2022. Its reporting adheres to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines for cross-sectional studies. Prescription data for MDIs and DPIs were obtained from regional healthcare databases, encompassing approximately 100 000 inhalers annually. The analysis focused on calculating the carbon emissions associated with MDIs by multiplying the quantity of HFA propellants used in each inhaler by their respective global warming potential (GWP) values, based on international environmental standards.⁴ For DPIs, the CO₂eq emissions were estimated using available emission factors from recent literature.⁵

Statistical analyses were used to assess the environmental impacts of MDIs and DPIs by comparing carbon emissions across inhaler types and medication classes. Additional information on prescription data handling, calculation approaches and analysis can be found in online supplemental materials.

Patient and public involvement

Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Results

This study analysed the distribution and carbon footprint of inhalers used in South Tyrol for asthma and COPD treatment during 2021 and 2022. A total of 199 914 inhalers were prescribed in 2021, with 45 031 MDIs (22.53%) and 55 747 DPIs (27.89%) accounting for 50.42% of all respiratory medications prescribed. In 2022, the total number of inhalers increased to 221 170, with 49 711 MDIs (22.47%) and 51 623 DPIs (23.34%), representing 45.81% of all inhalers (table 1). Online supplemental table 1 details inhaler prescriptions by active substance and type.

Table 1. Distribution of MDIs and DPIs as part of total outpatient respiratory drug prescriptions dispensed in South Tyrol (2021 and 2022).

Year	Total respiratory drug use	MDIs dispensed (% of total)	DPIs dispensed (% of total)	MDIs+DPIs (% of total)
2021	199 914	45 031 (22.53%)	55 747 (27.89%)	100 778 (50.42%)
2022	221 170	49 711 (22.47%)	51 623 (23.34%)	101 334 (45.81%)

DPIs, dry powder inhalers; MDIs, metered dose inhalers.

The carbon emissions generated by MDIs and DPIs differed significantly. In 2021, MDIs emitted a total of 1 007 793 kg CO₂eq, while DPIs emitted 55 747 kg CO₂eq. In 2022, MDIs contributed 1 101 915 kg CO₂ compared with DPIs’ 51 623 kg CO₂ (figure 1). This represents an increase of approximately 100 tonnes of CO₂eq from MDIs in 2022, while DPI-related emissions decreased slightly. Online supplemental tables 2 and 3 detail the CO₂eq emissions for each inhaler type and substance class for both years.

Figure 1. CO₂-equivalent emissions in tonnes from metered dose inhalers (MDIs) and dry powder inhalers (DPIs) dispensed in South Tyrol in 2021 and 2022.

The inhaled corticosteroids plus long-acting beta₂-agonists (ICS+LABA) combination inhalers were responsible for the majority of CO₂eq emissions, contributing 45.26% of the total MDI emissions in 2022. This was followed by short-acting beta₂-agonists (SABA) inhalers, which accounted for 39.85% of MDI emissions. In contrast, DPIs in the ICS+LABA category emitted a substantially lower amount of CO₂eq (table 2).

Table 2. CO₂-equivalent emissions by inhaler type and substance class in South Tyrol (2021 and 2022).

Substance class	Year	MDIs (kg CO2eq)	DPIs (kg CO2eq)	Total (kg CO2eq)
ICS	2021	67 568	709	68 277
	2022	89 546	732	90 278
LABA	2021	6983	3924	10 907
	2022	6671	2883	9554
ICS+LABA	2021	492 951	29 083	522 034
	2022	498 724	28 613	527 337
SABA	2021	389 117	N/A	389 117
	2022	439 153	N/A	439 153
LAMA	2021	N/A	17 071	17 071
	2022	N/A	13 984	13 984
ICS+LABA+LAMA	2021	24 604	849	25 453
	2022	30 235	1033	31 268
SABA+SAMA	2021	12 316	N/A	12 316
	2022	15 964	N/A	15 964
LABA+LAMA	2021	943	4111	5054
	2022	7166	4387	11 553

DPI, dry powder inhaler; eq, equivalent; ICS, inhaled corticosteroids; LABA, long-acting beta₂-agonists; LAMA, long-acting muscarinic antagonists; MDI, metered dose inhaler; SABA, short-acting beta₂-agonists; SAMA, short-acting muscarinic antagonists.

To further illustrate the impact of a potential transition, the CO₂eq savings were estimated that could be achieved if all MDIs dispensed in 2022 were replaced by DPIs, assuming a DPI emission of 1 kg CO₂eq per device. The greatest savings were observed in the ICS + LABA class, where replacing 23 751 MDIs could reduce emissions by over 426 000 kg CO₂eq annually. Other notable reductions include approximately 84 500 kg for ICS, 28 100 kg for ICS + LABA + LAMA, and over 6000 kg each for LABA and LABA + LAMA. Detailed results are provided in online supplemental table 4.

Discussion

This study measured the carbon footprint of inhaler use in South Tyrol, a region with around 540 000 residents, finding that MDIs produce significantly higher CO₂eq emissions than DPIs. Despite the small population, MDIs emitted over 1000 tonnes of CO₂eq annually in 2021 and 2022, while DPIs emitted less than 55 tonnes each year. These results highlight the considerable environmental impact of inhaler therapy in a healthcare system with an MDI to DPI ratio of about 1:1 and suggest significant CO₂eq reductions if patients switched from MDIs to DPIs. The findings support the study’s aim to assess the environmental benefits of transitioning from MDIs to DPIs, indicating that such a shift could notably decrease healthcare-related emissions, aiding climate change mitigation.

These findings are consistent with previous research, which demonstrated that MDIs disproportionately contribute to inhaler-related CO₂eq emissions due to their reliance on HFA propellants HFA-134a and HFA-227.^{6 7} In contrast, DPIs, which do not use propellants, have a significantly smaller carbon footprint. Studies have shown that countries such as the UK have already implemented national policies to promote DPI use.⁸ The data from South Tyrol support similar policy measures, as they reflect the environmental impact of MDI use in a local context. However, while switching to DPIs can be effective, it is critical to consider when and how this switch is implemented to maintain clinical efficacy.⁹

While environmental concerns are increasingly acknowledged, patients and clinicians primarily prioritise clinical efficacy, ease of use, safety and adherence when selecting inhalers. Environmental factors currently play a secondary role in decision-making.¹⁰ The clinical context is crucial when changing inhaler therapy. Transitioning stable, well-managed patients from MDIs to DPIs is possible with proper education and support. Herrera et al¹¹ suggest that stable patients are more receptive to learning new inhaler techniques with professional guidance, minimising treatment disruption and enabling a shift to eco-friendly inhalers. MDIs, often used with spacers, are recommended in acute settings for their ease of use and rapid action.⁵ A hybrid approach may be optimal, transitioning stable patients to DPIs while retaining MDIs for exacerbations to ensure effective symptom control and care continuity.

This study underscores the need for policies promoting a gradual transition to DPIs or more eco-friendly MDIs for stable patients to achieve environmental benefits without compromising care. Prescribing flexibility must be maintained, keeping MDIs available for acute exacerbations, especially for vulnerable populations such as the elderly, children or those with severe conditions who may require the rapid delivery of MDIs for effective symptom control. In addition, patient preference and inhaler cost can significantly affect adherence.¹² Poor adherence, in turn, may increase the risk of exacerbations, leading to greater use of carbon-intensive healthcare resources.¹³

The analysis also quantified the theoretical CO₂eq reductions achievable by switching all MDIs to DPIs within each drug class. The largest emission reductions were attributable to the ICS + LABA class, highlighting this combination as a key target for environmentally sustainable prescribing. Even smaller drug classes, such as LABA or LABA + LAMA, showed measurable benefits. These findings support interventions focusing on high-emission classes, which may yield substantial environmental gains without requiring a full system-wide switch. A full switch from MDIs to DPIs is unlikely due to clinical and patient-related factors. To reflect a more realistic approach, we estimated a 50% switch scenario. For ICS + LABA inhalers in 2022 alone, this would have saved over 213 000 kg CO₂eq. Even partial substitution in high-emission classes can yield substantial environmental benefits with minimal disruption to current prescribing practice.

In Italy, SABA medications are currently only marketed as MDIs, with no DPI alternatives available. As a result, all SABA prescriptions in South Tyrol relied on high-emission devices, making this class the second largest contributor to total inhaler-related CO₂eq emissions. The development or approval of SABA-DPI formulations could be a key strategy for further emission reductions.

South Tyrol’s inhaler prescription pattern, characterised by a balanced MDI:DPI ratio and predominant use of MDIs for SABA and ICS+LABAis broadly consistent with trends in Italy and other European countries such as Germany and France, where DPIs constitute around half of prescribed inhalers.¹⁴ This alignment supports the applicability of the findings to comparable healthcare systems aiming to reduce inhaler-related emissions.

A limitation of this study is its reliance on publicly available data for HFA propellant quantities, potentially missing variations across inhaler brands or patient adherence. Patient-level data were not available, preventing analysis of inhaler use or emissions per patient. The study did not include soft mist inhalers, which are propellant-free and therefore have minimal CO₂-eq emissions. Future research should explore the economic impact of switching to DPIs and assess patient preferences for different inhaler types.

This study confirms that transitioning from MDIs to DPIs has the potential to substantially reduce healthcare-related CO₂eq emissions in South Tyrol, with annual MDI emissions exceeding 1000 tonnes, comparable to the emissions from driving approximately 6 million km in an average passenger car. However, this environmental benefit must be weighed against patient-specific clinical needs. Blanket switching for all patients is neither feasible nor advisable; instead, transitions should be prioritised for patients who are stable on maintenance therapy and for drug classes where DPI alternatives exist. Clinicians should retain flexibility to prescribe MDIs when clinically necessary, particularly for acute symptom relief or in vulnerable populations such as children, the elderly or those with coordination difficulties.

Low-GWP propellants such as HFA-152a are expected from 2025 and could reduce MDI climate impact by over 90%. MDIs also remain essential for young children and are more easily recycled, offering complementary strategies to reduce emissions alongside switching to DPIs.^{15 16}

Future health policy should promote the use of low-emission inhalers within the framework of evidence-based prescribing and patient-centred care. From 2025, low-GWP propellants are expected to enter the market, potentially reducing the environmental burden of MDIs. These developments may further expand future options for climate-conscious prescribing.

Data availability statement

Data are available upon reasonable request.