Smog Choking Parisians Eased After Traffic Curbs, Study Shows

May 14, 2014 4:00 am ET

May 14 (Bloomberg) -- Traffic restrictions imposed in Paris for a day in March lowered emissions and alleviated smog choking the French capital.

The government’s partial ban on road traffic on March 17 during a period of increased pollution had a “quantifiable and visible impact,” according to Airparif, which monitors air quality. Overall air quality gauged by concentrations of the pollutants improved due to the measures, especially in neighborhoods closest to the often-congested Paris ring-road called the Boulevard Peripherique, the report said.

The findings could pave the way for curbing Parisian traffic more often to lessen smog caused by vehicle emissions trapped by weather conditions. The restrictions were the first of their kind taken by a French government in 17 years and included waiving public transport fares and suburban parking charges.

Recent pollution alerts in Paris have reignited debate over taxes on diesel fuel, which in France are lower than for gasoline. Environmental groups have urged the government to align the levies, while carmakers such as PSA Peugeot Citroen have resisted the move. Diesel produces more fine particulates that can pose health risks.

Airparif’s report published today was the first to evaluate the measures criticized by some commuters who were unable to use their cars. Airparif also released another study showing that while chronic pollution levels fell slightly in Paris in 2013 from the previous year, they regularly surpass what is deemed safe.

Odd Numbers

During the almost 18-hour period when cars with license plates ending in odd numbers were allowed in Paris and 22 surrounding towns, the level of pollutants known as PM10s dropped 15 percent, while there was a 20 percent fall in nitrogen dioxide emissions, Airparif said today. The decreases were smaller during the morning rush hour than in the evening.

While weather conditions weren’t optimal for the best results of the traffic ban, it led to “a real lowering of exposure to particulates and an even bigger decrease in exposure to nitrogen dioxides,” Airparif said. It also noted that the method of restricting traffic by license plate number didn’t allow for a weeding out of the most polluting vehicles.

For the whole of last year, air quality in the Paris region “remained problematic” with more than 3 million people potentially exposed to levels deemed unhealthy, Airparif’s report showed. The levels of chronic smog were on a “slightly downward trend” in part due to more favorable meteorological conditions.

Too-high levels of PM10s caused the most pollution alerts last year in Paris where the 50 microgram per cubic meter limit deemed unsafe was surpassed on 64 days on the Champs-Elysees and 139 days on the main A1 highway entering the capital from the north, according to the report.

France has been put on notice by the European Commission for not respecting rules on emissions of PM10, which refers to particulates less than 10 micrometers in diameter.

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