Automaker’s cheating added pollution equal to as many as 19 million cars in U.S.

Volkswagen AG bragged its diesel models were some of the cleanest on the highways. In fact, they added the equivalent of as many as 19 million chemical-spewing cars to American roads.

Based on the Environmental Protection Agency’s estimate that 482,000 vehicles in the U.S. were polluting as much as 40 times the legal limit, that equals almost 12,000 additional tons of nitrogen oxide pollutants per year.

“We are very concerned that there are a lot of emissions involved and the public is being harmed,” Frank O’Donnell, president of the non-profit advocacy group Clean Air Watch in Washington. “We are going to demand that the government forces Volkswagen to fix this.”

Estimates of additional pollutants emitted since 2009 raise questions about possible harm to human health and may become the basis for massive penalties sought by the EPA. Nitrogen oxides combine with other chemicals in the air to form the most common form of smog, which can cause a burning sensation in the lungs and trigger respiratory disease.

O’Donnell said his group believes the illegal emissions were so enormous that the U.S. government should force VW to find ways to make restitution, such as funding cuts of similar power-plant emissions.

“Paying a fine would not be adequate in our opinion,” he said. “They are going to have to come up with ways to reduce emissions further.”

The VW vehicles were programmed to activate pollution-control equipment while being tested for compliance with EPA and the California Air Resources Board standards, ensuring that emissions met legal standards. Afterward, the car’s software switched off the controls so the cars’ performance was maximized while allowing far higher pollutant levels.

Such software modifications are permitted in some cases, but must be disclosed to the EPA. VW didn’t tell EPA about the existence of the software until it was threatened with a halt to sales of its 2016 models, according to agency documents.