A breath of fresh AIR: reducing the carbon footprint of asthma

Healthcare systems globally contribute an estimated 4–5% of total greenhouse gas emissions [1]. As governments seek to curb emissions within their respective countries, healthcare systems – and respiratory departments in particular – are being asked to play their part. This is perhaps not unreasonable given the obvious paradox that many inhaled treatments contribute to global warming, which can in turn worsen the very conditions they treat [2].

For asthma, switching from inhalers with a high global warming potential, such as pressurized Metered Dose Inhalers (pMDIs), to alternatives with a lower global warming potential, such as Dry Powder Inhalers (DPIs), has gained significant traction as a means to reduce healthcare carbon footprints, with both the United Kingdom (UK) National Health Service and the British Thoracic Society encouraging this approach [3]. Indeed, the National Institute for Health and Care Excellence (NICE) estimate that the average pMDI carbon footprint is 25 times greater than for DPIs [4]. However, legitimate concerns remain about the impact of switching inhaler devices in people with well-controlled disease, as this could potentially worsen their condition [5].

The analysis by Kponee-Shovein and colleagues [6], published in this journal, is important in extending consideration of the carbon footprint in asthma beyond emissions from inhalers, to also include asthma exacerbations. Using previously published data, they calculated that the UK annual carbon footprint for asthma exacerbations of all severities was 724,201 tonnes of carbon dioxide equivalent (t CO₂e), with severe and life-threatening exacerbations accounting for 61.9% (448,037 t CO₂e) of the total [6]. Of note, healthcare encounters were the key contributor during an exacerbation, having a much greater impact on emissions than the type of reliever inhaler device used. This demonstrates how essential good asthma control is to driving down overall carbon emissions associated with asthma. It should also be noted, however, that the carbon footprint emission data for healthcare encounters, derived in part from Tennison et al. [1], are greater than those reported by the Sustainable Healthcare Coalition, and therefore may represent an overestimation of their contribution [7].

Although inhalers with low global warming potential, such as DPIs, should be the preference when starting or changing a person’s asthma inhaler medication, achieving good asthma control and preventing asthma exacerbations must remain the primary goal to improve both clinical and environmental outcomes. Fortunately, using DPIs and achieving good asthma control are not mutually exclusive. A recent post hoc analysis of the Salford Lung Study showed that people with moderate-to-severe asthma who switched to a DPI regimen had improved asthma control and reduced their annual carbon footprint by 55% compared with those continuing with pMDI treatment [8]. This should provide reassurance to clinicians and people with asthma that switching inhaler device can be done safely and without negatively impacting asthma control.

In addition to switching the type of device used in clinical practice, further reductions may be made by optimizing the therapeutic regimen in accordance with current Global Initiative for Asthma (GINA) recommendations; since 2019, low-dose inhaled corticosteroid (ICS)-formoterol, in a single inhaler, has been the preferred reliever therapy across all treatment steps for adolescents and adults with asthma [9]. Importantly, compared with traditional short-acting beta₂-agoinst (SABA) reliever-based regimens, this “Anti-Inflammatory Reliever” (AIR) approach with ICS-formoterol is associated with significant reductions in severe asthma exacerbations, across the spectrum of asthma severity, including in those with previously poorly controlled asthma [10–12]. It also has the advantage of requiring only a single reliever actuation per use episode, compared with the traditional two when a SABA is used. Although there have been no formal carbon footprint analyses for the AIR regimen to date, it is reasonable to hypothesize that a reduction in greenhouse gas emissions would occur with both the change from a SABA pMDI to an ICS-formoterol DPI reliever, and the reduction in exacerbations associated with healthcare encounters. The magnitude of the reduction may be considerable, as illustrated by the comparison between budesonide-formoterol and salbutamol reliever therapy in mild asthma, in which budesonide-formoterol DPI resulted in a 60% reduction in severe exacerbations, and about half the number of actuations from the DPI that has less than 5% the carbon footprint of the salbutamol pMDI per actuation [4,13]. The AIR regimen may therefore represent a means of decreasing both exacerbations and the carbon footprint associated with asthma, with the greatest gains seen in those switching from a traditional SABA pMDI reliever-based treatment regimen to an AIR DPI approach.

Reducing the carbon footprint associated with childhood asthma presents a greater challenge. As acknowledged by Kponee-Shovein and colleagues [6], their analysis would have been strengthened by including children; exacerbations and healthcare encounters in this group are frequent, particularly in those under five years of age [14], and undoubtedly represent a substantial contribution to the overall asthma carbon footprint. Unlike for adults, inhaler device switching is less suitable, due to the coordination and inspiratory efforts required to adequately use DPIs, particularly in the context of worsening asthma. DPI use may be attempted in older children, with some guidelines suggesting from eight years of age [15], but pragmatically reductions in children will likely be driven by moving towards pMDI propellants with a substantially lower global warming potential, such as hydrofluoroolefin (HFO)-1234ze [16].

The limited evidence for the ICS-formoterol AIR approach in children also needs to be addressed. To date, a single study has been published, involving children aged 4–11 years with moderate-to-severe asthma [17]. Compared with maintenance ICS-formoterol plus SABA reliever, ICS-formoterol maintenance and reliever therapy significantly reduced the risk of a severe asthma exacerbation requiring medical intervention by 75%. This benefit is greater than that demonstrated in adults in the same study [18], and may suggest greater efficacy of the as-needed ICS-formoterol component in children. It should be noted that the children in this study by Bisgaard and colleagues did use DPIs; however, it is unclear how many children were enrolled at each age and due to the DPI requirement, it is possible that most children were enrolled in the upper age bracket. ICS-formoterol pMDIs do exist and offer an alternative means of delivery, particularly in children. However, there is greater uncertainly if a pMDI-based AIR approach would help to reduce the carbon footprint, as they contain the more greenhouse gas-potent propellant, hydrofluoroalkaline (HFA)-227ea; at approximately 295 g CO₂e per actuation this has a substantially greater carbon footprint compared with 49 g CO₂e and 126 g CO₂e for small volume and large volume SABAs, respectively [19].

To achieve meaningful reductions in the carbon footprint associated with asthma, it is important to reframe the way asthma inhalers are prescribed and used, with greater consideration given to the treatment approach as a whole. Beyond switching from pMDI to DPI devices, ICS-formoterol AIR treatment may offer even greater reductions by decreasing the frequency of asthma exacerbations requiring healthcare encounters (a key driver of greenhouse gas emissions), compared with traditional SABA reliever-based regimens. Alongside efficacy, safety and patient preference, carbon footprint must be a consideration in clinical practice when deciding treatment options, as recommended by NICE [4].

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Declaration of funding

The Medical Research Institute of New Zealand receives Independent Research Organisation funding from the Health Research Council of New Zealand. No specific funding was received for this manuscript.

Acknowledgements

None reported.

Declaration of financial/other relationships

MRINZ received research funding from AstraZeneca, Genentech, Health Research Council NZ and CureKids NZ on behalf of RB outside of the submitted work.

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.