Image source does not exist News Release: 2010-08-31 Fine particle air pollution responsible for 9,000 premature deaths in California each year

Release #:10-48

ARB PIO: (916) 322-2990

Dimitri Stanich

Stanley Young

Fine particle air pollution responsible for 9,000 premature deaths in California each year

ARB report based on U.S. EPA peer-reviewed study

SACRAMENTO - Approximately 9,000 people in California are estimated to die prematurely each year as a result of exposure to fine particle pollution, according to a report issued today by the California Air Resources Board.

“There is no question particulate pollution is causing premature deaths here in California and nationwide,” said ARB Chairman Mary Nichols. “This study is further evidence that we are on the right track, and ARB will continue to work with truckers and equipment owners to clean up diesel emissions, improve our air quality and protect public health. ARB is committed to reducing this staggering statistic because one premature death is one too many.”

The ARB report and its methodology were based on recent science assessments completed by the U.S. EPA. These assessments were required as part of the federal agency’s periodic review of the national air quality standards for fine particle matter, or PM 2.5. The review, undertaken as a public process every five years, was completed this spring and included peer review by the federal Clean Air Scientific Advisory Committee.

As a result of this review, the U.S. EPA concluded that there is a causal relationship between exposure to fine particle pollution and premature death.  A causal relationship indicates the highest level of scientific certainty.

This initial U.S. EPA review was followed by a related risk assessment report released in June that estimated premature deaths nationwide from exposure to fine particulate pollution. The U.S. EPA and its Clean Air Scientific Advisory Committee considered evidence from multiple peer-reviewed studies, and the estimates of premature death were based on a key nationwide study of exposure to fine particle pollution involving about 500,000 people and 116 U.S. cities, including Los Angeles and Fresno. 

ARB used the same methodology and risk factors the peer-reviewed U.S. EPA report used and applied it to the entire state, drawing on California-specific data from 90 fine-particulate monitoring stations to estimate the number of premature deaths that can be linked to this pollution.

ARB’s report estimated that 9,200 premature deaths in California are associated with fine particulate pollution on an annual basis, with a statistical range from 7,300 to as high as 11,000 premature deaths each year.  California has the most extensive particulate monitoring network in the nation.   

Fine particle pollution, smaller than 2.5 microns—less than a human hair which averages 70 microns in diameter—is the product of a variety of sources including particles in the exhaust of diesel engines.

Very fine particulate pollution is particularly dangerous since it burrows deep into the lungs where it can enter the bloodstream and harm the heart and other organs.  Fine particulate pollution poses an especially critical health danger for children, the elderly, and people with existing health problems.  While it is recognized that exposure to PM 2.5 is linked to cardiovascular disease, the report focused only on premature deaths and did not estimate increased hospitalizations or other health impacts.

Illustration above shows very fine particulate pollution compared to the 70-micrometer diameter of human hair.

ARB efforts to reduce fine particulate pollution are driven by the need to protect public health and also by federal clean air requirements that mandate aggressive action to meet national clean air standards. Missing compliance deadlines could result in the loss of federal transportation funds and other federal sanctions.

In 1998, ARB declared particles in diesel exhaust a Toxic Air Contaminant, a designation that required the Board to take measures to reduce the risk. The Diesel Risk Reduction program was instituted by ARB in 2000. Since then ARB has adopted many regulations to reduce diesel emissions including those from trucks, construction equipment, cargo handling equipment at ports and rail yards, transit buses and trash trucks among others. 

The ARB has conducted extensive outreach through its website, The Truck Stop ( and the Diesel Hotline (866-6DIESEL) over the last year to ensure companies and truck owners are aware of available financial assistance.  In 2006, voters approved Proposition 1B, a $1 billion bond initiative to transition to cleaner technologies and clean up emissions from school buses, heavy-duty trucks and diesel equipment.  Additionally, up to $140 million annually is available through the Carl Moyer grants which are designated for early or extra emission reductions.  There is also a low cost truck loan program under AB 118 to help truckers access financing before regulatory deadlines. 

The ARB report can be found at
THE U.S. EPA report can be found at : .

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.