California's Diesel Risk Reduction Plan

This page last reviewed March 17, 2010


The Air Resources Board (ARB or Board) identified particulate emissions from diesel-fueled engines (diesel PM) as toxic air contaminants (TACs) in August 1998. Following the identification process, the ARB was required by law to determine if there is a need for further control, which moved us into the risk management phase of the program.

For the risk management phase, the Board directed staff to form the Diesel Advisory Committee to assist in the development of a risk management guidance document and a risk reduction plan. The Advisory Committee and its four subcommittees met many times to discuss control approaches. Representatives on the committee and its subcommittees consisted of staff from the ARB, United States Environmental Protection Agency, State and local agencies, industry, environmental groups, and interested public. In addition to formal committee and subcommittee meetings, ARB staff also met with individual stakeholders.

With the assistance of the Advisory Committee and its subcommittees, the ARB developed the Risk Reduction Plan to Reduce Particulate Matter Emissions from Diesel-Fueled Engines and Vehicles and the Risk Management Guidance for the Permitting of New Stationary Diesel-Fueled Engines . The Board approved these documents on September 28, 2000, paving the way for the next step in the regulatory process: the control measure phase.

During the control measure phase, specific statewide regulations designed to further reduce diesel PM emissions from diesel-fueled engines and vehicles will be evaluated and developed. The goal of each regulation is to make diesel engines as clean as possible by establishing state-of-the-art technology requirements or emission standards to reduce diesel PM emissions. The regulations will be developed in an open and public process where availability, applicability and cost of technology will all be evaluated. The interested members of the public, manufacturers, and other stakeholders will be asked to participate in the develpment of all proposed regulations.