The Dirty Truth About ‘Clean Diesel’

Volkswagen has been punished with consumer opprobrium, a costly recall and plummeting sales.  Yet the public outrage over the fraud obscures a much larger issue.

Volkswagen played a leading role in convincing people to accept a technology that in many countries is causing a precipitous decline in air quality for millions of city-dwellers: the diesel engine.  Monitoring sites in European cities like London, Stuttgart, Munich, Paris, Milan and Rome have reported high levels of the nitrogen oxides and particulate matter, or soot, that help to create menacing smogs.

Recently, officials in Milan temporarily barred cars from the city; in Rome, too, persistent smog has forced the authorities to limit the use of private vehicles.  Back in March, Paris was enveloped in a gray cloud of choking fumes that obscured the Eiffel Tower for hours and briefly earned the French capital the title of the world’s most polluted city, beating out even Beijing.  An air quality expert in Britain reported that much of it was “stale diesel” from traffic emissions generated in European cities.

This diesel pollution is not just unpleasant; it is also dangerous.  The nitrogen oxides produced by diesel engines, which are far more popular in Europe than in the United States, are a potent irritant for asthma sufferers.  Health officials in Italy also noted increased reports of cardiovascular disease this week.

Diesel exhaust is laden with insidious soot particles, the so-called PM 2.5 (particulate matter smaller than 2.5 microns, or one-thirtieth the width of a human hair), which allow carcinogens to penetrate deep into tissues and organs.  In other words, a driver who steps on the accelerator of a diesel car may be filling the lungs of nearby pedestrians, cyclists, infants in strollers and other drivers with potentially deadly particulate matter.

According to one study, 9,416 premature deaths in London in 2010 were attributed to nitrogen dioxide and PM 2.5 particles.  Annual deaths linked to air pollution in Britain as a whole now rival the death toll in the early 1950s, when “pea souper” fogs caused by coal fires shrouded the capital for weeks.
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In the United States, which has some of the world’s toughest air pollution laws, automakers worked hard to convince consumers that a new generation of “clean diesel” cars were far less polluting.  Volkswagen heavily promoted its “TDI” (turbocharged direct injection) technology.

We know better now.  As anybody who has seen the black smoke spewing out of the pipes of a big rig as it changes gears can testify, diesel has a fatal flaw.  It tends to burn dirty, particularly at low speeds and temperatures.  In cities, where so much driving is stop and start, incomplete diesel combustion produces pollution that is devastating for human health.

Fortunately, Volkswagen sold under half a million of its “clean diesel” cars to the American public before the emissions scandal broke.  Today, fewer than 1 percent of the passenger vehicles sold in the United States run on diesel fuel.

Read more at The Dirty Truth About ‘Clean Diesel’