Release 08-29
April 24, 2008

    Leo Kay

ARB looks ahead to proposed landmark truck regulation after Board hears West Oakland health assessment
Diesel emissions from freeway trucks are major contributors to poor air quality

OAKLAND - Members of the Air Resources Board today emphasized the importance of passing a proposed state regulation before the Board later this year aimed at cleaning up emissions from 300,000 private diesel trucks after hearing a presentation from staff on additional health risks posed to West Oakland residents primarily by trucks transiting local freeways.

The study, developed in collaboration with the Bay Area Air Quality Management District, the Maritime Port of Oakland and Union Pacific Railroad, reveals that the estimated lifetime potential cancer risk for residents of West Oakland from exposure to diesel emissions is about 1,200 excess cancers per million people. The analysis covers 3.1 million people who reside in the affected area of 3,800 square miles. 

While diesel trucks account for a majority of the risk in West Oakland resulting in about 850 potential cancer cases per million or 70 percent, port operations account for an estimated lifetime potential cancer risk of 200 excess cancer cases per million, or about 15 percent of the total. Union Pacific railyard emissions amount to a potential cancer risk of about 40 excess cancer cases per million, or less than 5 percent and the remaining 10 percent of risk comes from a variety of diesel sources such as passenger trains and construction projects.

"This health assessment strenghtens our resolve to clean up the estimated 300,000 diesel trucks currently spewing health-threatening soot throughout the state," ARB Chairman Mary Nichols said. "If we fail to pass this regulation, West Oakland residents will continue to be endangered by this huge unregulated source of diesel emissions."

In the development of the ship emissions, ARB staff used transponder data (continuously reports ship location) to more accurate estimate where off-shore emissions are occurring.  For the first time in a large risk assessment, a regional wind field was generated using data from 30 onshore and 3 offshore weather stations. The CALPUFF model was used to estimate the ambient concentration of diesel particulate matter.  This model is capable of producing more precise results than the models used in the past due to its ability to account for highly varying wind fields and complex terrain.

Emissions from diesel particulate matter are associated with causing a variety of health effects including premature death and a number of heart and lung diseases. The study also estimates the yearly non-cancer health impacts resulting from exposure to port-related diesel particulate matter emissions in the area: 18 premature deaths (age 30 and older), 290 asthma attacks, 2,600 days of work loss, and 15,000 minor restricted activity episodes. 

Having identified diesel particulate matter as a toxic air contaminant in 1998 due to its potential to cause cancer and other respiratory problems, ARB has put in place stringent regulations to curve the health risk to Californians.  The most recent adopted regulations to limit diesel emissions affect cargo handling equipment, transport refrigeration units, truck idling, off-road equipment, harbor craft, ship auxiliary engines, port drayage trucks and ships-at-berth.  Also, the introduction of cleaner fuel for railroads and ships has contributed to lower pollution around the ports and railyards.

Later this year, ARB will be considering proposed regulations involving on-road heavy duty diesel vehicles (trucks and buses) and ocean-going vessel main engines to further reduce diesel soot.  State control measures will contribute to an approximate decrease of 80 percent in harmful emissions by 2015. 

For more information on the West Oakland health risk assessment, please visit

The Air Resources Board is a department of the California Environmental Protection Agency. ARB's mission is to promote and protect public health, welfare, and ecological resources through effective reduction of air pollutants while recognizing and considering effects on the economy. The ARB oversees all air pollution control efforts in California to attain and maintain health based air quality standards.