California Air Resources Board

SACRAMENTO - Specific components of particles may be linked to the progression of heart disease, the leading cause of death in the U.S., according to a study released today by the California Air Resources Board. 

Funded by the Air Resources Board and led by Dr. Michael T. Kleinman of the University of California Irvine, the study used a novel approach to look at health impacts associated with exposure to particles, 0.18 microns in diameter or smaller. A human hair is about 60 microns in diameter, or at least 300 times wider than the diameter of particles examined in the study. 

The particles examined in this study are a subset of particle pollution known as PM10 and PM2.5, particulate matter that is equal to or less than 10 and 2.5 microns in diameter, respectively. 

Numerous scientific studies have linked exposure to PM2.5, which can be deeply inhaled into the airways and lungs, to a variety of problems, including premature death, especially in people with pre-existing heart disease. 

The particles used in this study, which come primarily from internal-combustion exhaust and from chemical reactions in the air, may pose a great health risk, yet relatively little is known about the emissions, exposures or health effects of these ultrafine particles. In the UC Irvine study, scientists used a heating method to remove most of the organic chemical compounds from particles, leaving behind most inorganics to examine the health effects of these particles’ component parts. Laboratory mice exposed to either fully intact particles or just the organic components of the particles had more rapid development of atherosclerotic plaques, compared to mice exposed to particles without the organics. The intact particles also had other negative effects on heart health. Atherosclerosis is hardening of the arteries, a factor contributing to heart attacks.

Dr. Kleinman, professor and co-director of the Air Pollution Health Effects Laboratory from the Division of Occupational and Environmental Health, Department of Medicine, UC Irvine, was the principal investigator on the study, titled, “Cardiopulmonary Health Effects: Toxicity of Semi-Volatile and Non-Volatile Components of PM.”

The study provides information that is significant to help the Air Resources Board expand its understanding of the role of different components of exhaust emissions so that the ARB can better target control policies. Reducing particulate matter air pollution is one of California’s highest public health priorities. 

ARB’s Advanced Clean Cars and diesel control programs are reducing emissions of this harmful pollution. Projected emission reduction benefits associated with full implementation of ARB’s Diesel Risk Reduction Plan are reductions in diesel particulate matter emissions and associated cancer risk of 85 percent by 2020, compared to 2000 levels.

Dr. Kleinman presented his findings at a seminar on October 9, 2013, at the Cal/EPA Headquarters Building, 1001 I St., Sacramento. The presentation and the report can be viewed at: http://www.arb.ca.gov/research/seminars/kleinman2/kleinman2.htm