Natural PM Events: Dust and Smoke Background and Rationale Smoke from C. American Forest Fires PM10 over the Eastern U.S. during the smoke event The Asian Dust Event of April 1998 Asian Dust over the West Coast Resource Links Contact: Rudolf Husar,

Background and Rationale Dust storms and forest fires are major PM events that occur several times a year over different parts of the US. Many of these events originate outside the US, e.g. dust from Sahara and the Asian desserts and smoke from forest fires in Central America and Canada. Exceedances of the NAAQS caused by dust and smoke events are uncontrollable ‘acts of God’. Nevertheless, states are required to provide evidence that such events (outside their jurisdiction) have occurred. For this reason, control agencies need to be able to detect and document the impact of such events on their control region. The existing tools for such documentation are poorly developed. The natural PM events are illustrated by two extreme examples: Asian dust impacting on the West Coast and the Central American forest fire smoke impacting the Eastern US.

Smoke from C. American Forest Fires During a ten-day period, May 7-17, 1998, smoke from fires in Central America drifted northward into USA and Canada. The smoke caused exceedances of the PM standard, health alerts, and impairment of air traffic, as well as major reductions of visual range. It has been argued that some ozone exceedances in the Eastern US may have been due to ozone generated by the forest fire smoke. GOES 8 View of the Smoke SeaWiFSSeaWiFS View of the Smoke

PM10 over the Eastern U.S. during the smoke event

The Asian Dust Event of April 1998 On April 15th, 1998 an unusually intense dust storm began in the western Chinese Province of Xinjiang, just in time for the east Asian dust season. By April 20, the dust front covered a 1000 mile stretch on the east coast of China and within five days it moved across the Pacific. It reached the West Coast by April 25.

Asian Dust over the West Coast In Vancouver and in Washington State the PM10 and PM2.5 concentrations reached 100 an 40 ug respectively. Based on public complaints and monitoring data, the State of Washington has issued a ban on open burning on April 29.

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