The pollution that has hit Paris for the last week has seen the highest levels of fine particles and nitrous oxide for at least 10 years, Airparif announced on Wednesday, adding that it has also lasted longer than any such incident for a decade.
With fine-particle pollution at 146 microgrammes per cubic metre, Thursday 1 December was the worst day, the organisation said.
Lyon and the Alps around Chambéry and Annecy have also been badly hit.
Paris restricts traffic
Traffic restrictions in Paris and the surrounding region were prolonged on Wednesday,
Air pollution, the facts:
- Air pollution is the third cause of death in France, after smoking and alcohol.
- Fine particles can cause cancer and set off asthma, allergies, breathing and heart problems.
- Nitrous oxide, which is present in the fumes of diesel engines, can set off asthma attacks and problems for children's lungs.
- The current spell is caused by people using more heating because of the cold, vehicle exhaust fumes, a lack of wind and the trapping of pollutants near the ground because air close to the ground is, unusually, cooler than that higher up.
with vehicles with even-numbered registrations banned between 5.30am and midnight, after a ban on odd numbers on Tuesday that failed to prevent traffic jams, some of them "exceptional", in the evening.
Police booked 1,746 motorists for ignoring the ban by the middle of Tuesday afternoon.
The restrictions could continue on Thursday, regional official Michel Cadot warned, while forecasters said the conditions that have led to the pollution - an anticyclone that is affecting much of western Europe - were likely to last until the weekend.
Lyon on Wednesday announced that it would implement the same system alternating registration numbers as from Friday.
City and region disagree
When the alternating traffic system was enforced in March 2014 it cut fine-particle pollution six percent and nitrous oxide 10 percent, Airparif says.
This week's ban was declared later than the Socialist-controlled Paris city council would have liked because the right-wing-controlled regional council was loath to introduce it until the regional préfecture declared it was necessary, according to Le Monde newspaper.