All cars will be banned from the Champs-Élysées on the first Sunday of every month, as part of an ongoing effort to combat air pollution across Paris. The car ban along Paris' most famous boulevard was approved in February and had been slated to go into effect this Sunday, but the mayor's office said Tuesday that it will be delayed until May 8th. May 1st is a national holiday in France, and many of the city employees needed to operate the event will be off work, city hall said.

Socialist Mayor Anne Hidalgo has made the environment a priority since assuming the office in 2014, backing ambitious plans to create more pedestrian zones and ban diesel cars in Paris by 2020. The French capital held its first "day without cars" in September 2015, banning vehicles from some major boulevards in the city, and Hidalgo has said the event will be expanded "to all of Paris" this September.

A temporary measure with temporary effects

Paris and other European cities have seen smog levels spike to dangerous levels in recent years, forcing some to implement temporary car bans. Officials in Milan banned private cars from city streets for a few hours a day last year, while Oslo plans to permanently ban motorists from the city center by 2019.

There is evidence to suggest that these efforts have a short-term effect on pollution levels. Airparif, the air quality monitoring agency for the Paris region, found that nitrogen oxide levels declined by between 20 and 40 percent during the no-car day in September, though a UCLA study on temporary car bans found that the effect on pollution is short-lived.

The World Health Organization says fine-particle air pollution is responsible for an estimated 42,000 deaths in France each year. A report from the French Senate last year estimated that air pollution costs the country €100 billion ($112 billion) each year, largely due to health costs.