Asthmatics have been warned by health chiefs that each inhaler they use could be polluting the environment by as much as a 180-mile car journey.

The National Institute for Health and Care Excellence (Nice) has issued new guidance urging sufferers, where possible, to avoid using the most popular type of inhaler, known as a metered dose inhaler (MDI).

Making up around 70 per cent of inhaler prescriptions - approximately 26 million a year - MDIs contain propellants known as hydrofluorocarbons, which are powerful greenhouse gasses.

The first time Nice has assessed the carbon footprint of a recommended device, the body calculated that five doses from a MDI have the same carbon emissions as a nine-mile trip in a typical car.

The devices usually contain 100 doses.

By contrast, dry powder inhalers are only around one fifth as bad for the environment.

Nice said most types of asthma medication are available in more than one type of inhaler and urged users to consider switching away from MDIs.

Professor Gillian Leng, deputy chief executive, said: “People who need to use metered dose inhalers should absolutely continue to do so, but if you have a choice of a green option, do think about the environment.

“Cutting carbon emissions is good news for everyone, especially those with respiratory conditions.”

The new guidance also encourages asthmatics to return used inhalers to local pharmacies for environmentally safe disposal or recycling.

More than 5.4 million people in the UK receive treatment for asthma, including 1.1 million children.

Britain has some of the highest rates in Europe, with around three people a day dying as a result of the condition.

Other European countries rely on MDI devices far less than in the UK, including Sweden where they make up just 10 per cent of inhaler prescriptions.