Ancient lead emissions polluted Arctic.

Researchers have discovered lead emissions from ancient Roman and Greek smelters buried in British peat and Swedish lake sediments (SN: 3/26/94, p.198). But a new study shows that ancient airborne pollutants traveled even farther and contaminated the lower atmosphere of the lower Arctic.

"This...marks the oldest large-scale hemispheric pollution ever reported," Sungmin Hong of Domaine University in Grenoble, France, and his colleagues assert in the Sept. 23 SCIENCE.

The team analyzed cores drilled by the European Greenland Ice Core Project in central Greenland. Lead production increased during a period of Roman cultural expansion 2,500 to 1,700 years ago. Lead concentrations reached a high of about 2 picograms per gram (pg/g) of ice during the 800-year span. This is nearly four times the amount found in ice dating to before people began working lead.

At its peak, lead production in ancient Rome totaled about 80,000 metric tons per year, rivaling the output during the Industrial Revolution, the Hong group calculates. Roughly 400 tons of lead accumulated in the Greenland ice cap between 500 B.C. and A.D. 300. In comparison, some 2,670 tons of lead have fallen on Greenland over the past 60 years, mostly due to the use of lead additives in gasoline, the team reports.

Lead concentrations in ice cores fell between A.D. 300 and A.D. 500, following the depletion of the Roman lead mines, the team finds. But the concentrations later increased because of lead and silver mining in Central Europe, reaching almost 4 pg/g in ice samples from 1,000 to 500 years ago.

Lead concentrations in core samples from when Greek civilization flourished over 2,500 years ago rival those found in segments from Roman times. But since the Greeks made less lead, either lead production estimates are incorrect or lead emissions traveled more readily to Greenland from the Greek production sites, the team speculates.