China's top court has underscored the critical need to control and prevent air pollution, calling on judges to continue cracking down on illegal activities tied to vehicle emissions.

The Supreme People's Court said vehicle emissions, particularly nitrogen oxides and particulate matter, are major contributors to air pollution and public health risks, often exceeding standards when released.

On Tuesday, the court released details of three prominent cases and instructed courts nationwide to impose heavy penalties on polluters while strengthening environmental restoration efforts.

In one case, a vehicle inspection company in Xinhua county, Hunan province, used a diagnostic system simulator and emissions cheating software in December 2022 to falsify reports, allowing more than 400 vehicles that should have failed emissions tests to pass. Authorities found the company had been penalized twice in the past two years for issuing fraudulent emissions documents.

A local court fined the company 300,000 yuan ($41,829) for air pollution and sentenced key personnel, including the manager, supervisors and the employee who procured the software, to prison terms ranging from eight to 18 months, along with additional fines.

The top court said the case represented the judiciary's determination to punish vehicle inspection agencies that issue false reports, emphasizing that these agencies are "guardians of compliance with vehicle emission standards" and play a key role in reducing emissions from mobile sources.

Penalizing violators helps combat disorder in the vehicle inspection sector and cleanse the third-party environmental protection services market, the court said, adding that the rulings demonstrate the judiciary's commitment to cleaner air.

In another case, a man surnamed Li in Longyou county, Zhejiang province, leased 12 cars between March and May 2022, then swapped out the catalytic converters for substandard products in his auto repair shop before returning the vehicles to the rental company. He also sold the original converters.

After discovering the tampering, the company reported the case to police but did not stop renting out the cars. Police later urged the company to conduct emissions tests and repairs on the affected vehicles.

In August 2023, the Longyou court sentenced Li to 16 months in prison for theft and fined him 5,000 yuan. Li and the rental company were also ordered to pay about 7,000 yuan for air quality restoration, as the excess nitrogen oxide emissions from the tampered vehicles totaled more than 227 kilograms.

"These penalties serve as a warning to the vehicle repair and leasing industries to operate in compliance with emissions regulations," the top court said. "The ruling also shows the commitment to using legal means to support efforts in preventing and controlling mobile source air pollution."