Authorities have raised an air pollution alert for the Spanish city of Barcelona, a major tourist draw which has lain for days under a toxic grey mist, an official said Tuesday.
"High atmospheric pressure and a lack of wind are preventing the dispersal of polluting emissions, which are accumulating over the city," said a spokeswoman for the Catalonia regional government.
As the mist obscured the city skyline, the government issued an alert in a bid to reduce gas emissions, said the spokeswoman, who asked not to be named.
It lowered the speed limit for traffic, urged citizens to use public transport and asked factories to reduce their activity in the city of 1.6 million residents.
The level of toxic nitrogen oxide gas in the air had risen above the European Union legal limit seven times since December 4, the spokeswoman said, adding however that these exceptional rises did not threaten people's health.
Barcelona draws millions of tourists a year for its nearby beaches and city sights such as the decorative architecture of Antoni Gaudi, including the Sagrada Familia cathedral.
But it also has one of the densest concentrations of motor vehicles in Europe and pollution gets trapped by the surrounding mountains, the spokeswoman said.
The alert was due to stay in force at least until Thursday.
Explore further: NOAA: Warm oceans cause concern of coral bleaching