Introduction
Asthma and chronic obstructive pulmonary disease (COPD) are the most common chronic respiratory diseases and are among the leading causes of morbidity and mortality, worldwide.1 It is estimated that there are at least 300 million patients with asthma and 328 million patients with COPD.2 3 Inhalers are important devices that reduce morbidity and mortality associated with these diseases and significantly improve quality of life.4 5
International recommendations advocate a tailored, personalised approach for choosing the most suitable inhaler for each patient.2 6 The two main classes of inhaled medications are bronchodilators (short-acting and long-acting β2-agonists and antimuscarinic agents) and inhaled corticosteroids (ICS), each delivered as single agents or in combination via a handheld inhaler. New therapeutic approaches administered through the inhaled route are also in development.
Inhaled therapies are necessary as key components of asthma and COPD treatment, but currently their contribution to greenhouse gas emissions, and hence global warming, is being discussed.7 8 The three principal types of inhalers are: pressurised metered-dose inhalers (pMDIs; used with or without holding chambers or spacers, some are breath-actuated), dry-powder inhalers (DPIs; reservoir, multi-dose and single-dose rechargeable) and soft mist inhalers (SMIs). For all these device types, carbon footprint can be calculated throughout the life cycle of the product, including raw materials, production, transport, use and waste disposal.7 8 The use of pMDIs relies on the driving force of propellants to atomise droplets containing drugs for deposition in the lungs.9 The propellants used in pMDIs are hydrofluorocarbons (HFCs), which are greenhouse gases and for this reason the carbon footprint of a pMDI is higher than a DPI or SMI, with the use and disposal phases providing the larger contribution.7 8 However, even after considering this, it is calculated that the use of pMDIs accounts for <0.1% of total global greenhouse gas emissions.10–13 In contrast, drug delivery with DPIs and SMIs occurs without a propellant, and thus their carbon footprint is mainly dependent on the raw materials and manufacturing process.7 8
Carbon dioxide equivalent (CO2e) is the unit for comparing the radiative forcing of a greenhouse gas (GHG) to that of CO2. The mass of a GHG is converted into CO2e by multiplying by the corresponding global warming potential (GWP).14 In some countries, there is a drive to reduce CO2e emissions by restricting the use of pMDIs and encouraging the use of DPIs.15 However, changing inhaler class has important implications for patients, since pMDIs are more suitable for many patients because of, for example, inhaler type, insufficient inspiratory flow rate, or handling capabilities and individual preference.16 Moreover, switching from pMDIs to DPIs could have other environmental impacts, including human toxicity, marine eutrophication and fossil depletion.8 Therefore, there is an unmet need to ensure that patients continue to receive the most effective and appropriate treatment while also reducing the negative impact of inhalers on the environment.
Deciding on the optimal choice of inhaler for each patient is essential to maximise treatment outcomes; such complex decisions are shared between the healthcare practitioner and patient.4 5 Changing treatment to a different type of inhaler class can have negative impacts on patients and may lead to reduced medication adherence.17 Conversely, simplifying treatment strategies and minimising inhaler options may have a positive effect on disease control in some patients; therefore, it is important to consider a patient’s individual circumstances before initiating a switch.18 The European Respiratory Society (ERS) acknowledges the environmental impact of pMDIs, but stresses the need for a multifaceted approach, focusing on patient safety and choice rather than just focusing on the device.19
Novel approaches are being considered to reduce the carbon footprint of pMDIs, to balance environmental goals with patient health and well-being.9 The development of pMDI devices that contain low-GWP propellants, while optimising the quality of patient care, is one focus.20 21 The hydrofluoroalkane (HFA) propellant, HFA-152a, has a substantially reduced GWP100 (GWP over 100-year time horizon) of 138.13 Replacing the current propellants in pMDIs, HFA-134a (GWP100, 1300) and HFA-227ea (GWP100, 3350) with HFA-152a (GWP100, 138), which would reduce GWP by 89% and 96%, respectively,13 would result in carbon emissions within the range of DPIs.8 Consideration should also be given to inhaler recycling since environmental impact can be reduced through recovery of leftover propellant.22
To understand the extent to which different courses of action could lead to reductions in greenhouse gas emissions associated with pMDIs, thereby decreasing their carbon footprint, we conducted a series of scenario analyses using asthma and COPD inhaler sales data from 2019 to model emissions reductions over a 10-year period for five reference markets: the UK, Italy, France, Germany and Spain.