What the VW Scandal Means for Clean Diesel

When Volkswagen debuted the so-called “clean diesel” Jetta TDI sedan and wagon in 2009, it was regarded as something of a breakthrough. The company claimed its new diesel technology would reduce emissions—most notably soot and nitrogen oxides (NOx)—without disrupting the car’s exemplary efficiency or performance.

We now know that unsuspecting owners of some 500,000 VW diesel cars in the United States—and as many as 11 million worldwide—were all the while subjecting themselves and others on the road to extraordinarily high levels of the emissions that cause smog. The company’s CEO apologized after the U.S. Environmental Protection Agency revealed that VW used technology to produce overly forgiving results during smog tests that did not match emissions on the road.

The EPA found the VWs actually emit 40 times the standard rates of nitrogen oxides. It’s difficult to say just how damaging that was, but there is no doubt that NOx—when combined with volatile organic compounds and in the presence of sunlight—creates ground-level ozone, otherwise known as urban smog.

There is wide consensus that smog is a cause of asthma among children—and for those already affected by asthma, especially older people, smog can be fatal.

Late last year, the EPA proposed strengthening the 2008 smog standard. After lawsuits by environmental organizations in 2013, and an order by the U.S. District Court in April 2014, the EPA is expected to take final action on stricter smog standards by October 1, 2015.

Daniel Greenbaum, president of the Health Effects Institute, an independent nonprofit research firm based in Boston, says he wasn’t surprised by the challenges facing automakers in keeping NOx in check. His organization is funded by the EPA, the auto industry, and other private funders. “What surprised me was the planned deception,” he says. “It’s sad that a manufacturer would go so far to do this.” Greenbaum is also chair of the board of directors for the International Council for Clean Transportation, the organization that first alerted the EPA and the California Air Resources Board about high levels of pollutants from two of VW’s popular diesel models, the 2012 Jetta and 2013 Passat.

Efficient diesel vehicles, while popular in Europe, were for decades barred from the all-important California market becaue of stringent laws aimed at smog—the foul haze that enveloped Los Angeles for decades. When Volkswagen and other automakers said that the new diesel vehicles were “clean,” and backed that up by robust green marketing campaigns, Americans’ long-held belief that all diesel vehicles spewed black smoke from tailpipes started to lift. Diesel sales grew from about 79,000 vehicles in 2010 to nearly 140,000 last year.

VW became a leader in the U.S. diesel market, largely because it promised efficiency and safe emissions with no compromise in axle-twisting torque. Other companies offering diesel either used relatively more expensive urea treatment systems to reduce the impact of NOx or reduced performance to meet pollution standards.

Diesel cars are very efficient, burning less fossil fuel—and therefore reducing greenhouse-gas emissions per mile relative to most gas-powered cars. Yet it’s unlikely that they will ever be as clean as hybrids or electric cars, especially when it comes to local air quality. With the filters, scrubbers, and special treatment systemsinvolved in so-called “clean diesel” technology, they can come closer. But the VW scandal reveals that at least some reduction in performance might be required. VW’s “no compromise” message now rings false.

More importantly, Dieselgate will likely bring unprecedented public attention to the detrimental impact of smog-forming NOx emissions. While not visible like plumes of black clouds and not carcinogenic like particulate matter, high NOx emissions will nonetheless become a reason for U.S drivers to steer clear of diesel cars—regardless of how much fun they are to drive.