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A narrative review conducted by Urrutia-Pereira et al¹. examined the environmental impacts of inhaler devices used in asthma and COPD management by synthesising recent literature on inhaler-related carbon emissions. As part of this, the authors presented CO₂ equivalent emissions per puff according to the pharmacological agent and device type.

Here is what they found:

Why Switch?

Environmental Impact

Figure 1 highlights that the ICS+LABA pMDI has substantially higher CO₂e emissions per puff than the DPI and SMI alternatives shown. This large difference is not due to the active medication, but due to the hydrofluoroalkane (HFA) propellant used to aerosolise the drug in pMDIs, contributing to more than 95% of the pMDI global warming potential.² The commonly used pMDI propellants HFA-134a and HFA-227ea have global warming potentials approximately 1300 and 3350 times greater than CO₂ respectively, as they release potent greenhouse gases.³ Therefore, where clinically appropriate, selecting lower-emission devices can reduce the environmental burden of inhaler therapy without targeting or restricting the medication patients need.

A 12-week study conducted by Janson et al⁴, measured the effects of switching patients with asthma and COPD from pMDI based treatment to a DPI based treatment.

Here is what they found:

Table 1: Clinical outcomes following transition to lower-emission inhalers adapted from Janson et al⁴.

Outcome Parameter

ACT mean

FEV1% mean

(asthma)

Mini-AQLQ mean

Reliever Use per day median (asthma)

CAT mean

FEV1% mean

(COPD)

mMRC mean

Baseline

13.3

76.7

55.1

0.4

23.5

51.3

2 12 Weeks

21

87.1

78.2

0.1

16.8

58.8

1 P Value

< .0001

N/a

< .0001

ACT = Asthma Control Test: ≤ 15 very poorly controlled, 16–19 not well controlled, and > 20 well controlled.

FEV1% = Measure of amount of air exhaled in the first second expressed a percentage of total air exhaled.

Mini-AQLQ = Mini Asthma Quality of Life Questionnaire: Higher scores indicate a better quality of life.

Reliever use per day = amount of times a day patients used reliever medications.

CAT = COPD Assessment Test: > 20 indicates a high impact of COPD on daily life.

mMRC = Modified medical research council (mMRC) dyspnea scale: > 1 indicates difficulty in walking due to breathlessness

Health Outcomes

Table 1 shows the benefit of switching asthma and COPD patients from pMDI based treatment to a DPI based treatment. Among asthma patients, the ACT score shifted from poorly controlled asthma to well-controlled asthma. This improvement indicates that patients experienced fewer symptoms, better day-to-day control, and a reduced impact of asthma on their daily activities. Lung function also improved, with mean FEV₁ increasing, suggesting improved airway function following the switch to a DPI. In addition, Mini-AQLQ scores increased substantially, reflecting improvements in physical, emotional, and social aspects of living with asthma. Daily reliever inhaler use decreased, indicating that patients relied less frequently on rescue medication due to improved symptom control.

Patients with COPD also experienced clinically meaningful benefits. CAT scores decreased, demonstrating a reduction in the overall impact of COPD symptoms on patients’ quality of life. Mean FEV₁ improved, indicating better pulmonary function following the transition to a DPI. Furthermore, median mMRC scores decreased, suggesting reduced breathlessness and an improved ability to perform everyday physical activities.

Additionally, Janson et al⁴ found that patient satisfaction was higher with DPIs, with 99% of asthma patients and 94% of COPD patients rating their DPI as good or very good, compared with 39% and 45%, respectively, for their previous pMDIs.

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Brand et al⁵ conducted a randomised four-way crossover study involving patients with moderate-to-severe COPD. The study compared the whole lung and oropharyngeal deposition of bronchodilator medication delivered using a SMI and a pMDI. Drug deposition was measured using gamma scintigraphy to determine how effectively each device delivered medication to the lungs.

Here is what they found:

Figures adapted from Brand et al⁵.

Figures 2 and 3 demonstrate SMIs delivered medication more efficiently than the pMDIs. As shown in Figure 2, whole lung deposition increased after training with the SMI, whereas lung deposition with the pMDI remained unchanged despite training. This suggests that the SMI is less dependent on perfect inhaler technique and that appropriate patient education can further enhance its performance.

Figure 3 shows that oropharyngeal deposition decreased following training with the SMI, indicating that less medication was deposited in the mouth and throat and more reached the lungs. In contrast, the pMDI showed no change in oropharyngeal deposition, suggesting no improvement in delivery efficiency after training. Together, these findings support the use of SMIs to improve pulmonary drug delivery while reducing medication loss in the upper airway.

These findings suggest that, for some patients, lower-emission devices can support effective respiratory care while reducing inhaler-related emissions. Device choice should still depend on clinical suitability, inhaler technique, patient preference, cost/access and

follow-up.

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Legend

SMI

pMDI

Trained

Untrained

Evidence about lower-emission inhaler switching varies by patient group, device type and clinical context. Lower-emission inhalers are not suitable for every patient, and switching should not occur during unstable disease, acute exacerbation, poor inhaler technique, inability to use the alternative device, or strong patient preference not to switch. This resource supports shared decision-making and does not replace clinical judgement, current Australian guidelines or PBS checks.

Limitations

Reference list

Urrutia-Pereira M, Chong-Neto HJ, Winders TA, Solé D. Environmental impact of inhaler devices on respiratory care: a narrative review. J Bras Pneumol. 2022;48(6):e20220270. doi:10.36416/1806-3756/e20220270
Emeryk AW, Sosnowski TR, Kupczyk M, Śliwiński P, Zajdel-Całkowska J, Zielonka TM, et al. Impact of inhalers used in the treatment of respiratory diseases on global warming. Adv Respir Med. 2021;89(4):427-438. doi:10.5603/ARM.a2021.0092
Scottish Government. Respiratory conditions - quality prescribing strategy: improvement guide 2024 to 2027: environmental impact of inhalers. Scottish Government. April 22, 2024. Accessed June 21, 2026. https://www.gov.scot/publications/quality-prescribing-strategy-respiratory-guide-improvement-2024-2027/pages/12/
Janson C, Hisinger-Mölkänen H, Tamasi L, Vartiainen V, Lehtimäki L. Switching to the dry powder inhaler: disease control with a lower carbon footprint. Pulm Ther. 2025;11(4):753-763. doi:10.1007/s41030-025-00319-w
Brand P, Hederer B, Austen G, Dewberry H, Meyer T, Schulze A. Higher lung deposition with Respimat Soft Mist inhaler than HFA-MDI in COPD patients with poor technique. Int J Chron Obstruct Pulmon Dis. 2008;3(4):763-770. doi:10.2147/COPD.S3930