PARIS -- After a week of escalating actions to try to curb a pollution crisis, culminating with a temporary ban Monday of nearly half the city's cars, Paris is again breathing easy.

Minister of Ecology Philippe Martin said late Monday that 90 percent of Parisian drivers followed the rules, which allowed for only cars with odd-numbered license plates to drive around Paris and its outlying suburbs. "Bravo, and thank you," Martin said while announcing that the restrictions, which the ministry originally considered continuing through yesterday with even-numbered cars, would end Monday night.

The move was an inconvenience for many drivers and a money-loser for some businesses, such as filling stations, but the bright side was clearer air and profits for a few companies as commuters strove for alternatives. Autolib, the electric car sharing service in Paris, saw a 60 percent increase in new subscribers last week, reported spokeswoman Laëtitia Fevry. On Friday, the Parisian Velib, a citywide public bike rental program, saw 130 percent greater demand than usual.

Other cities across Western Europe, however, are still struggling with high levels of pollution. The greatest concern over the last week has been with the rising levels of particulate matter of less than 10 microns in diameter (PM10), which can cause reduced visibility, environmental damage including accelerating some impacts of climate change, and significant respiratory distress. These fine suspended particulates "are capable of penetrating deep into the respiratory tract and causing significant health damage," the World Bank reports.

Near-real-time air quality maps showed Antwerp, Belgium, reached PM10 levels of 99 micrograms per cubic meter between 4 and 5 a.m. yesterday. The European Environment Agency classifies all PM10 values above 65 as "very high."

Across the region, spikes in levels are fluctuating dramatically. Near Geneva, initial reports of PM10 concentrations showed levels as high as 310.8 between 4 and 6 p.m. Monday.

In Stockerau, Austria, PM10 levels reached 372 between noon and 1 p.m. Saturday, fell during the weekend, then spiked again to 310 between noon and 1 p.m. Monday.

Incentives for electric vehicles
The move to reduce emissions began in Paris on March 11 with regulations to allow for free residential parking, followed by free public transportation and discounts and free time on the use of bike and electric car sharing programs. On Friday, however, the industrial sector of Paris, La Defense, saw PM10 levels of 165.

The World Bank reports that, in 2009 and 2010, the average annual exposure level of PM10 in France was 12; the United States' level, for comparison, was 18 during this time and China's was 59.

Most particulate matter pollution originates from diesel trucks and cars, wood stoves, and power plants. But the particles themselves can be a combination of many different components, including sulfates, nitrates, organic carbon, elemental carbon, soil dust and even sea salt.

When high emissions couple with certain weather conditions, such as the weeklong stable front that brought warm, sunny days and clear, cool nights across much of Western Europe, pollution can accumulate to dangerous levels. Higher temperatures can increase the oxidation rates of these compounds in the lower atmosphere, allowing for a greater buildup of oxidants.

While short-term efforts to curb emissions and increase use of public transportation can help improve conditions while waiting for the weather to change, ultimately rain and wind are needed to disperse the pollution and bring atmospheric concentrations back to their average levels. But that such high spikes have been seen across Western Europe during this recent stable weather brings into focus the long-term consequences of fossil fuel subsidies.

Disincentives for diesel fuel?
In a study on the taxation of diesel cars in Belgium, authors Inge Mayeres and Stef Proost of Katholieke Universiteit Leuven found that CO2 emissions are reduced, but in a very cost-inefficient way.

"We find that diesel cars are still taxed much less than gasoline cars, resulting in a dominant market share for diesel cars in the car stock," the authors reported last year in the journal Energy Policy.

"If the fuel tax is the main instrument to control for externalities and generate revenues, the diesel excise should be much higher than the excise on gasoline for two reasons: diesel is more polluting than gasoline and more importantly, through the better fuel efficiency, diesel cars contribute less fiscal revenues per mile."

Alternatively, in this year's April issue of the journal, a study on the long-term climate policy implications of phasing out fossil fuel subsidies argues that changes in taxation need to go hand in hand with strong, dedicated climate policies.

"Most remarkably we find that a removal of fossil fuel subsidies, if not complemented by other policies, can slow down a global transition towards a renewable based energy system," report Valeria Jana Schwanitz and colleagues at the Potsdam Institute for Climate Impact Research in Germany.

"The reason is that world market prices for fossil fuels may drop due to a removal of subsidies. Thus, low carbon alternatives would encounter comparative disadvantages."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500