It’s not just Volkswagen. Every diesel car company is emitting more pollution than tests show.

Tens of thousands more premature deaths a year than we thought
Tens of thousands more premature deaths a year than we thought
Image: AP Photo/Michel Euler
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The certification tests for diesel vehicles may be one giant loophole.

Cars, trucks, and buses running on diesel pass the government emissions tests in the lab just fine—and then go on to emit noxious pollution far beyond the legal limit once they hit the road. To be clear, it is not just Volkswagen: A report from UK regulators last year found that no other car manufacturer tested had installed “defeat devices,” the software Volkswagen used to intentionally cheat on tests, but every car assessed was found to spew more nitrogen oxides (NOx) on the road than in certification tests. Mitsubishi recently admitted to cheating on emission tests in Japan, the US accused Fiat Chrysler of a similar scheme, and Peugeot Citroen and Daimler are under investigation by French and German prosecutors, respectively, for possibly cheating diesel emissions testing.

By now, it has begun to dawn on the regulatory community that illegal levels of emissions may be an industry standard. And according to a study published Monday in the journal Nature, global NOx emissions from diesel vehicles may be more than 50% higher than regulators thought.

Researchers combed through emissions data from diesel cars, trucks, and buses sold in Australia, Brazil, Canada, China, the 28 EU member states, India, Japan, Mexico, Russia, South Korea, and the US. That covers about 80% of the diesel vehicles sold globally. Scientists recorded the data while the vehicles were on the road, using technology like sensors that attach to tailpipes—and compared those results to regulatory emissions test thresholds in those regions, which all the cars technically “passed.”

In total, light duty (cars) and heavy duty (trucks and buses) combined, legal limits would suggest diesel vehicles emitted 8.6 million metric tons of NOx in 2015. But according to the researchers’ calculations, they emitted 13.2 million metric tons.

“It’s a much more systemic problem than just cheating on the test. Whether you fake your way through this test, or you legally pass this test, the test is insufficient,” says Daven Henze, an atmospheric chemist at the University of Colorado Boulder and an author on the study. He stopped short of calling the epidemic of inaccurate diesel tests cheating, instead blaming poor test designs that don’t represent real-world driving. “It’s a loophole.”

The consequences of that loophole are lethal: It’s basic medical knowledge that air pollution causes people to die early. Researchers have already published death-toll forecasts for Volkswagen’s decision to rig 11 million vehicles with defeat devices. But once the global scale of the industry-wide problem is taken into account, the death toll becomes much, much larger.

Henze and his colleagues used data from NASA’s Earth-observing satellites AQUA and TERRA to model the spatial distribution of diesel pollution, determining how the harmful chemicals move across the globe once they’re put into the air. Combining that with regional driving trends, cars sold, and basic scientific knowledge of how pollution exposure harms health, they concluded that diesel emission caused an extra 38,000 early deaths in 2015 compared to previous estimates.

Regionally, that broke down to 11,500 in the EU, 10,600 in China, 9,300 in India, and 1,100 in the US. For comparison, air pollution from all sources was estimated to cause 4.4 million people globally to die early in 2015. (Previous research estimated Volkswagen’s cheating alone would result in 1,200 early deaths in Europe per year and another 60 in the US.)

Without major reform, the problem is only going to get worse. In many countries, more restrictive emissions standards are planned to be phased in in the next decades, and demand for diesel vehicles is expected to rise—meaning the gap between reported emissions and real-world emissions is set to get larger and larger moving forward. The researchers calculate the global early-death rate from diesel vehicles would be well over 100,000 annually by 2040.

Some governments—notably those in many European countries and California—are moving to implement stricter emissions limits and new test designs that use portable sensors attached to cars. Now that the scale of the problem is becoming clearer, Henze hopes governments will go above and beyond their intended reforms.

In their paper, the researchers laid out their pie-in-the-sky vision for the future: If countries chose to adopt what Henze’s team calls “next-generation standards,” which basically would combine very strict limits with the best available on-the-road test technology, NOx emissions would be “nearly eliminate[d],” avoiding 174,000 global premature deaths in 2040.