Cruise ships pumped four times more harmful sulphuric gases into the atmosphere in Europe than passenger vehicles last year, according to new research showing air quality is deteriorating despite emissions limits and industry pledges to go green.

A total of 509 tonnes of sulphur oxides were emitted by the 218 cruise vessels in operation across Europe last year, up from 465 tonnes of emissions linked to the industry in 2019, the last year of normal activity before the pandemic, according to a report by climate lobby group Transport & Environment.

A 0.5 per cent cap on sulphur content in marine fuels introduced in 2020 by the International Maritime Organization has helped to cut sulphur emissions per tonne of fuel consumed. But dozens of extra cruise ships have been added to the main operators’ fleets since 2019, which has increased total emissions. This is despite passenger volumes in Europe not yet rebounding to pre-pandemic levels.