The Environment Ministry plans to submit a bill to the Diet to amend the current vehicle emissions law by imposing tougher controls on commercial users of diesel-powered vehicles, ministry sources said Monday.

The new measures to be proposed include tightening emission levels for particulate matter and compelling companies to reduce the number of diesel vehicles they run, the sources said.

The ministry expects to submit the amendment to the ordinary session of the Diet, following its endorsement by the government in early February, according to the sources. They added that the ministry aims to put the law into force during fiscal 2002.

This marks the first time the government will include particulate matter as an object of emission standard regulations for diesel-powered vehicles, whose exhaust fumes contain nitrogen oxides and particulates that are believed to cause asthma and other respiratory diseases.

According to the sources, the government will be required under the amendment to impose the new air-quality standards in those areas worst affected by air pollution caused by emissions from vehicles.

In the designated regions, users of diesel-powered vehicles will be compelled to switch to vehicles emitting lower levels of pollution after the new law comes into effect, the sources said. They also said that vehicles registered in the regions are those that will be subject to the new rules.

New regions likely to be targeted include Nagoya and its vicinity, joining areas already subject to environmental standards under the current law, enacted in 1992, such as the Tokyo metropolis and the Osaka and Hyogo Prefecture areas.

Specific municipalities to be affected will be determined by a government ordinance at a later date.

Prefectures connected to the designated regions will have to draw up draft reduction plans by 2010 -- as well as midterm plans five years from the enforcement of the amendment -- based on the central government's basic environmental policy.

Businesses using more than a specified number of diesel-powered vehicles will be required to submit plans to reduce their diesel fleets by switching to low-emission vehicles. They will also need to submit plans outlining more efficient use of their vehicles.

Failure to comply with the new regulations could result in a fine of up to 500,000 yen.

The government is responding to increased public concern regarding poor air-quality in areas around highways. This concern has manifested itself in a number of ways, including demands brought against municipalities for compensation by citizens who claim that air pollution has caused serious damage to their health.