84 Scientific American, October 2020102550100300(^1000) B.C
. (^200)
B.C.
(^01)
(^00)
(^200)
(^30)
0
(^40)
0
(^50)
0
(^60)
0
(^70)
0
80
0
90
0
100
0
1100
(^140013001200)
(^150)
0
(^160)
0
17
00
18
00
190
0
2000
1972: Implementation
of U.S. Clean Air Act,
followed by similar
laws worldwide
1989: Economic declines
leading to 1991 Soviet
Union breakup
1940–1970: Widespread
rise of coal burning and
leaded gasoline
1939: World War II
1929: Great Depression
1918: Influenza
pandemic
1914: World War I
1000
950
900
85
0
(^150)
(^100)
(^50)
0
200
Greenland
Severnaya
Zemlya
(Russian Arctic)
SOURCES: “LEAD POLLUTION RECORDED IN GREENLAND ICE INDICATES EUROPEAN EMISSIONS TRACKED PLAGUES, WARS, AND IMPERIAL EXPANSION DURING ANTIQUITY,” BY J. R. MCCONNELL ET AL.,
IN PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES USA,
VOL. 115, NO. 22; MAY 29, 2018; “PERVASIVE ARCTIC LEAD POLLUTION SUGGESTS SUBSTANTIAL GROWTH IN MEDIEVAL SILVER PRODUCTION
MODULATED BY PLAGUE, CLIMATE, AND CONFLICT,” BY J. R. MCCONNELL ET AL., IN
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES USA,
VOL. 116, NO. 30; JULY 23, 2019
GRAPHIC SCIENCE
Text by Mark Fischetti | Graphic by Nadieh Bremer
Heavy Metal History
Abrupt changes in lead pollution highlight
dramatic world events
Ice cores from Greenland and the Russian Arctic show an ever chang-
ing amount of airborne lead pollution that has wafted northward from
Europe, Asia and North America each year. Lead levels tracked monu-
mental events in human history, including Phoenicia’s expansion in
1,000 b.c., the Roman Empire’s rise, terrible plagues and the industri-
al revolution. From antiquity to the 1800s, emissions came primarily
from smelting silver-bearing lead. For example, the Romans wanted
silver, so lead “was released to the atmosphere as waste,” says Joe
McConnell of the Desert Research Institute in Nevada, who led two
studies of the data. Burning coal and smelting for leaded gasoline
and paint from the 1940s through the 1970s boosted levels far beyond
any in history, until regulations such as the U.S. Clean Air Act cut
emissions. The COVID-19 pandemic may not leave much of a mark,
because many economies are largely deleaded.
17 b.c. to a.d. 195:
Roman Empire
High emissions persist
during the empire’s zenith,
when peace prevails, but
fall beginning around
165 as the Antonine
plague widens,
thought to be
measles or smallpox.
1349 to 1360: Black Death
The bubonic plague kills
a third of medieval Europe’s
population, reducing
labor to produce metals
and demand for them.
Low emissions continue
for a century.
1530 to 1560: Revival
Silver mining makes
a comeback, led by
Saxons in northeastern
Germany, yet a series
of epidemics curtails
economic activity again.
740 to 814:
Age of Charlemagne
Pepin I, king of the Franks,
ramps up silver production
for coins; his son
Charlemagne becomes
an emperor who controls
much of western Europe
until his death in 814.
835 to 1016:
Feast or Famine
Less pollution from 875
to 905 coincides with
drought, reducing food
supply and mining
activity. Then
Germany ex
ploits abundant
lead and silver
deposits, until
mines are aban
doned as famine
spreads in the
early 1000s.
Annual Lead Pollution
(captured in ice cores)
Note: Time before Year 0
is compressed; time after
0 is progressively
stretched for legibility.
Greenland
Severnaya Zemlya
(Russian Arctic)
Micrograms
of lead per
square meter
per year
1840 to 1850: Revolution
Economic crises and
oppression by monarchs
fuel the 1848 political
revolutions in France, Italy,
the Austrian Empire and
Germany. The industrial
revolution then pushes
pollution steadily upward
from about 1850 on.
Location of Cores
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