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Pressurised metered dose inhalers (pMDI) contain hydrofluorocarbon (HFC) propellants that do not have an effect on the ozone layer but are powerful greenhouse gases and can contribute to global warming.
Dry powder inhalers (DPI) do not use these propellants and have substantially lower global warming potential, producing 20g CO2 equivalent (CO2eq) per dose compared with 500g CO2eq for pressurised metered dose inhalers.
Estimated carbon footprints for comparison indicate an average trip (9 miles) in a typical car produces 2,610g CO2eq (or 290g CO2eq per mile).
As Breath Actuated Inhalers (BAIs) contain the same propellants as pMDIs, the estimated carbon footprints for pMDIs can reasonably be extrapolated to BAIs. Available data consistently show that there is a significant difference between DPIs and pMDIs / BAIs, and due to the absence of HFC propellants, DPIs have a low carbon footprint compared to other inhalers.
The Respimat device is a soft mist inhaler (SMI) that does not contain propellants, and so also has a lower carbon footprint than pMDIs and BAIs.
pMDI use in England is responsible for nearly 1 million tonnes of CO2 equivalent per year.
The NHS Long Term Plan identifies a shift to lower carbon inhalers as a way of significantly reducing the carbon footprint of health and social care.
With this in mind, dry powder inhalers or soft mist inhalers are generally preferred locally, unless there is a specific clinical or dexterity reason that an individual requires a pMDI or BAI.
In young children, a pMDI and a spacer is the preferred method of delivery; a face mask is required until the child can breathe reproducibly using the spacer mouthpiece. A pMDI plus spacer is also recommended for patient of any age for the treatment of mild and moderate acute asthma attacks. Other factors to consider include the choice of drug, patient preference, and acquisition cost.
NICE has produced a patient decision aid to help people with asthma and their healthcare professionals discuss their options for inhaler devices (available here), which includes consideration of the carbon footprint of the inhaler. It is suitable for use by people aged 17 years and over, and many of the considerations are also applicable to patients with COPD.
Used pMDI canisters still contain propellants; all used pMDI canisters should be returned to a pharmacy (or dispensing GP practice) to dispose of in an environmentally safe way.
Used inhalers should not be placed in general waste.
Used inhalers that are not returned to pharmacies but are placed in general waste for kerbside collection may end up in landfill, depending on local authority arrangements. As well as plastic pollution, this risks crushing or piercing the pMDI / BAI canister and releasing additional propellants into the atmosphere.
Inhalers should be placed in the pharmacy's pharmaceutical waste bins, which are incinerated (destroying the greenhouse gases); steel and aluminium may be recovered and recycled at some incinerators. Spacers cannot currently be recycled.