The Diet enacted legislation Tuesday that expands the scope of an air pollution law to cover particulate matter from diesel-burning automobiles and increases the responsibility of vehicle owners.

The new legislation, passed by the House of Representatives during an afternoon plenary session, adds particulate matter — tiny particles contained in the sooty exhaust of diesel vehicles — to the nitrogen oxides currently regulated under the Law Concerning Special Measures for Total Emissions Reduction of Nitrogen Oxides from Automobiles in Specified Areas.

The House of Councilors has already given the legislation the green light.

Particulate matter has been implicated as a cause of respiratory maladies, including asthma, and is believed to be a carcinogen.

Regulations will be expanded to include diesel-powered cars for the first time, and standards for trucks and buses will be stiffened. Corporations and large-fleet operators will be obliged to provide a plan on particulate emission reduction and submit them to the governor or, in certain cases, the transport minister.

The revisions also add greater Nagoya to the list of 196 municipalities — in six prefectures of the Kanto and Kinki regions — subject to its standards.

The revised law comes on the heels of the Tokyo Metropolitan Government's diesel regulations, aimed at cleaning up air in the capital amid a string of air pollution lawsuits against the state.