California Air Resources Board

SACRAMENTO – Today the California Air Resources Board (ARB) announced the results of a long-term research project that suggests that particulate matter (PM) transported from Asia contributes to the total amount of particulate matter in California air.

"The conclusion of this research project confirms the global nature of the atmospheric pollution problem," said ARB Chairman, Alan Lloyd. "It truly is a global phenomena and we are intimately linked with our neighbors around the world."

ARB research has shown that during the spring and summer, at two remote high-altitude sites not exposed to pollution from the United States, PM from Asia makes up over 60 percent of the PM10 mass and more than 80 percent of the PM2.5 mass. On average, Asian PM contributions are equal to about one-quarter of California's health-based air quality standards for PM10 and PM2.5. While these levels are not a significant threat to health, the data provides a link between the atmospheric makeup of our state and natural and human events in Asia.

Analysis of data has shown that PM from Asia is transported to California air by way of multiple atmospheric processes. The natural PM is accompanied by particles created from biomass burning, urban and industrial emissions. More research is needed to better understand this effect. Many questions remain such as what role climate plays in the frequency and intensity of the transport.

California's annual standard for PM10 is no more than 20 micrograms per meter cubed, and the annual standard for PM2.5 is no more than 12 micrograms per meter cubed.