Dust from the Sahara – wedded to high levels of air pollution that reached a maximum “level 10” – made London’s smog-like conditions even more visible on Thursday.
The famous landmarks and the city’s people choked for a second day.
In February the European Commission took legal action against the UK for failing to reduce nitrogen dioxide levels.
Other parts of Europe have been suffering too. Northern Germany was also affected with a thick layer of smog visible across the city of Hamburg.
Winds from the Atlantic are expected to blow in cleaner air by the weekend.
Meanwhile the UN Secretary General was in Brussels,urging the EU to work harder to cut greenhouse gas emissions.
“I think you can move this climate change process much faster,” Ban Ki-moon said. “My aim, my priority, is to put all of these locomotives on the right track and let them move so that we will be able to have a very effective and globally legally binding treaty on climate change by 2015, next year.”
Ban Ki-moon’s goal is to reduce greenhouse gas emissions enough to limit a global temperature rise to two degrees Celsius.