California Diesel Risk Reduction Plan

In 1998, the California Air Resources Board (CARB) designated diesel exhaust a toxic air contaminant after an exhaustive, 10-year scientific assessment process (CARB, 1998). Using the newly developed cancer risk assessment for diesel, CARB estimated that diesel particulate matter (PM), or soot, was responsible for 70 percent of the state’s risk of cancer from airborne toxics (2000). These alarming statistics spurred CARB in 2000 to develop its comprehensive Diesel Risk Reduction Plan, which calls for reducing diesel PM 75 percent by 2010 and 85 percent by 2020 (from the base year 2000 level).

The plan has three major components: first, to require low-sulfur diesel fuel (no more than 15 grams of sulfur per million grams of diesel fuel); second, to develop or implement emission standards for new diesel engines that will reduce PM by 90 percent; and third, to require that existing engines use pollution controls where technically feasible and cost-effective. In addition, the plan recognizes the important role of voluntary incentive programs in reducing diesel pollution.

Regulations

Between 2001 and 2007, CARB approved new regulations for more than 10 diesel fleets including transit buses, refuse haulers, transportation refrigeration units, stationary engines, portable engines and off-road equipment. As a result of these regulations and the anticipated emission reductions, CARB estimates some 6,300 premature deaths may be avoided over the next 10 to 20 years.

 
A particulate filter system approved under the Diesel Risk Reduction Plan   

CARB has had to overcome significant barriers to develop these regulations. These programs have often faced vigorous opposition from regulated industries and diesel equipment owners. The process of developing regulations can last years, as regulators evaluate technical options for reducing pollution, controlling costs, minimizing impacts on small businesses, and other issues.

California still has a long way to go to clean up diesel pollution as it has yet to implement pollution control requirements for the single largest diesel source in the state, heavy-duty trucks.  Rule development is currently underway on a truck regulation.