Obama ordered Volkswagen to recall nearly a half million cars

The Obama administration on Friday ordered Volkswagen to recall nearly a half million cars from the road, saying the German automaker used software intentionally designed to circumvent environmental standards for reducing smog.

The Environmental Protection Agency issued the company a notice of violation and accused the company of breaking the law by installing software known as a “defeat device” in 4-cylinder Volkswagen and Audi vehicles from model years 2009-15. The device is programmed to detect when the car is undergoing official emissions testing, and to only turn on full emissions control systems during that testing. Those controls are turned off during normal driving situations, when the vehicles pollute far more heavily than reported by the manufacturer, the E.P.A. said.

“Using a defeat device in cars to evade clean air standards is illegal and a threat to public health,” said Cynthia Giles, the E.P.A.’s assistant administrator for the Office of Enforcement and Compliance.

“Working closely with the California Air Resources Board, E.P.A. is committed to making sure that all automakers play by the same rules. E.P.A. will continue to investigate these very serious violations.”

The software was designed to conceal the cars’ emissions of the pollutant nitrogen oxide, which contributes to the creation of ozone and smog. The pollutants are linked to a range of health problems, including asthma attacks and other respiratory diseases.

The state of California has issued a separate notice of violation to the company. California, the E.P.A. and the Justice Department are working together on an investigation of the allegations.

The allegations cover roughly 482,000 diesel passenger cars sold in the United States since 2009.