Eurasian Air Pollution Reaches Eastern North America

Science, Vol. 290, No. 5500, p. 2258-2259, 2000 

P.E. Biscaye, A. Bory
Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
F.E. Grousset
Département Géologie et Océanographie, UMR 5805 EPOC, Université Bordeaux I, 33405 Talence, France.
A.M. Svensson
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.

Pollutants of Eurasian origin cross the Pacific Ocean via the westerly winds and affect the west coast of North America, as Kenneth E. Wilkening, Leonard A. Barrie, and Marilyn Engle discuss in their Perspective (Science's Compass, 6 Oct., p. 65). However, neither anthropogenic pollutants nor natural dusts of trans-Pacific origin stop their transit at or near the western North American coast.
We have found that the continental dust in the Greenland Summit ice cores from 1500 to 44,000 years before the present, and probably beyond, is of Eastern Asian provenance (1). We are finding the same sources in recent (past decade) dust extracted from snow pits at the North Greenland Ice Core Project site (75oN 43oW), including dust from the April 1998 outbreak shown in the figure in Wilkening et al.'s Perspective (see the figure) (2). The fluxes of dust to Greenland have been generally about a few milligrams per square centimeter per thousand years, compared with fluxes about an order of magnitude greater upwind in the eastern North Pacific (3). Consequently, we expect that the decrease in the flux of dust and associated pollutants between western and eastern North America might be less than that factor of ~10 and therefore of significance to levels of pollution.
As Asian economic expansion increases the quantities of pollutants injected into the westerly winds, their levels in western North American cities, like those cited by Wilkening et al., will also rise, as will those levels eastward and all across the continent.