It has become increasingly more evident that carmakers must take aggressive steps to ensure that diesel cars and light trucks meet current environmental regulations.

Tests done by Emissions Analytics found that the majority of new diesel-powered cars sold in Europe do not meet the Euro 6 emission standards for nitrogen oxides (NOx) in real-world use.

Worse, some of them emitted as much as 12 times the current levels when tested in real-world driving—and didn’t meet even the far lower Euro 3 standards from decades ago.

Diesel vehicles have been under more scrutiny since the world’s largest car manufacturer, Volkswagen Group, was caught using “defeat device” engine-management software to pass tests.

The deception was discovered by the University of West Virginia’s Center for Alternative Fuels Engines and Emissions (CAFEE) during independent research trying to prove that automakers could meet the NOx emissions standards.

Emissions Analytics, like CAFEE, tested vehicles independently under real-world conditions to see if they met the new Euro 6 standards. Their disturbing results are published by the EQUA Index.

The Emissions Analytics real-world tests found that only 16 of 116 diesel vehicles tested meet the Euro 6 emission standards for NOx, as depicted in the EQUA Air Quality Index chart.

Ony 14 additional vehicles would have met the standards even if the less stringent Euro 5 standards were used, giving a total of just 30 vehicles meeting a now-obsolete regulation under real-world driving conditions.

But the most disturbing part of the results may be how many cars exceeded the limits by wide margins.

More than half the 67 vehicles tested met only the decades-old Euro 3 emission limits.

Against the newly imposed Euro 6 limits, 21 of the cars tested exceeded the maximums with emissions that were at least six times the allowable limits.

Ten of the 21 worst-performing cars had emission levels 12 times or more the limits set under the Euro 6 standards.

Read more: Green Car Reports

Economists call them “externalities.” They’re the costs of people’s actions on other people or communities—though the people taking those actions don’t have to pay for those costs, even as they harm others.

The emissions from combusting fossil fuels to propel vehicles are clearly a prime example.

While complaints about air quality in the Los Angeles Basin date back centuries, research established more than 50 years ago that vehicle emissions were the primary cause of photochemical smog.

That led the state of California to begin efforts to regulate tailpipe emissions—well before the U.S. Environmental Protection Agency even existed—which led in turn to the first catalytic converters in U.S. vehicles in 1975.

Catalysts spread throughout most of the automaking world over the next 20 years, hugely reducing emissions of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), all toxic in various ways.

It’s well established that electric cars have the lowest wells-to-wheels CO2 footprint of any near- or medium-term alternative, varying from the equivalent of about 35 miles per gallon on the dirtiest U.S. grids to more than 100 mpg on the cleanest grids.

And the carbon footprint per mile of driving an electric car declines every time the grid gets cleaner, whether from adding renewable energy sources or replacing a coal-fired generation plant with one using natural gas.

With increasing availability of zero-emission cars over the coming years, when will citizens at large start to question the idea that every vehicle has an “exhaust pipe” that just belches harmful substances into our shared air?

And when will driving a car that emits carbon dioxide every time it moves become morally unacceptable?

Read more: Green Car Reports