Pressurised asthma inhalers and the environment

Pressurised asthma inhalers contribute very little to global warming

There is a lot of pressure for doctors to prescribe dry powder inhalers rather than pressurised dose inhalers – this is potentially harmful and may increase contribution to global warming. The reason for this advice is to protect the environment; however asthma inhalers contribute very little (less than 0.1%) to global warming. Furthermore, someone who cannot use a prescribed inhaler there is a risk of having an asthma attack. The downside is that treatment of asthma attacks then contribute substantially to global warming. So simply switching people from pressurised inhalers to dry powder types without ensuring they can be used correctly is potentially harmful for the environment.

There are two main kinds of inhalers

Pressurised metered dose inhalers (pMDIs) and dry powder inhalers (DPIs). The pMDIs contain propellants called Fluorinated Gasses (F-Gasses). F-gasses contribute to global warming, however the pMDIs contribute less than zero point one percent (<0.1%) of global warming potential.  Our GINA Lancet paper discusses future risks posed for people with asthma because of new regulatory proposals to limit availability of F-gasses for medical use.

There is an environmental crisis

The UK Government announcement that new oil drilling licences are being considered and last year an announcement was made on the news that a new coal mine is to be opened in the UK. However, peoples lives are potentially being threatened by recommendations to change people’s asthma inhalers ‘to save the planet’.

 Discussion to reduce use of pMDIs

There is currently a lot of discussion about the environment and the effect of the F-Gasses on the potential for global warming. These F-Gasses are used mainly for industries such as those in air conditioning and heat pumps, and a very small proportion of these gasses are used as propellants in pressurised metered dose inhalers (pMDIs) used for treating lung diseases like asthma and chronic obstructive pulmonary disease (COPD).

 Inhaled medication is essential for people with lung disease

Ensure people can use their inhaler correctly

These inhaler devices are necessary and in fact essential for controlling the symptoms of these lung diseases and for preventing attacks that can lead to hospitalisation and sometimes death. So it is essential that people are shown how to use their inhaler correctly and this cannot be done if these are switched without a face to face consultation.

 Not everyone can use all of the inhaler devices

Many people, including doctors and nurses, cannot use inhaler devices correctly. Therefore the patient’s needs should be the first consideration when changing from a pressurised inhaler to another type. As the pressurised inhalers contribute very little to global warming clinicians should think carefully before switching someone to a device they cannot or will not use.

 Many people argue that doctors should be prescribing dry powder inhalers(DPIs)

Doctors are encouraged to prescribe dry powder inhalers (DPI), instead of pMDIs.

 Lifestyle versus life-saving argument

This switch from pMDIs to DPIs is justified by statements comparing the global warming effect of a pMDI with a journey by car or aeroplane. For example see the advice from NICE, see here.

 The unintended consequences of switching people inappropriately to inhalers they cannot or don’t want to use

One of the main risks of people not using their inhaler correctly is that they may have an asthma attack/exacerbation/flare-up – which could be life threatening.

Treating asthma attacks contribute to global warming
Global warming impact of treating an asthma attack

 Treatment of asthma attacks have consequences for global warming

 The arguments for switching inhalers from pMDI to DPI do not include unintended consequences such as asthma attacks and the global warming potential resulting from their treatment.

Estimates derived from one paper :

 Example calculation of the effect of an asthma attack on the environment: (with help from Patrick Henry Gallen)*

  • Average number of days spend in hospital per asthma discharge in the UK: 3.4 (OECD 2018)
  • Number of asthma-related hospitalisations in the UK: 94.6 per 100,000 population = ~63,694 hospitalisations (OECD 2018)
  • Average CO2e for newly registered vehicles: 121.3 g/km (Department for Transportation 2015)
  • Hypothetical journey: 16.09 km/10 miles (5 miles to and from hospital)
  • Hypothetical number of journeys and visitors: 2 visitors visiting twice

Example of Global warming potential due to treating an asthma attack

  • 507.8 kg CO2e per hospitalisation
  • 32,343,813 kg CO2e / 32343.8 tonnes CO2e per year due to asthma hospitalisations in the UK

 Note that this model does not into account emissions related to a possible outpatient trip prior to hospitalisation or emissions related to inhaler usage and other devices or maintenance/manufacturing thereof (e.g. O2/nebulisers).

Further evidence of hospital care of an asthma attack and its contribution to the environmental footprint: see which concludes “The ICU generates more solid waste and Greenhouse Gasses (GHGs) per bed day than the acute care unit. With resource use and emission data, sustainability strategies can be effectively targeted and tested. Medical device and supply manufacturers should also aim to minimize direct solid waste generation.”

Choose the right inhaler for the patient

Our our GINA Lancet paper makes it clear that the patients needs must be prioritised when choosing an inhaler.

Global initiative for asthma inhaler choice figure
Inhaler selection – first ensure what is best for a patient


When considering prescribing inhalers for asthma the most important thing is to select one that the patient likes and can use properly. One of the consequences of getting this wrong is that the person may have an asthma attack which may be very serious. In addition the treatment of an asthma attack contributes adversely to global warming.

  • I was priveledged to work with Patrick on the severe asthma index of the Copenhagen Institute for Futures Studies