Europe: air pollution for 2,000 years

Increased lead levels long before the industrial revolution

The Colle Gnifetti in the Alps - an ice core from this glacier provided data on the development of lead contamination in the last 2, 000 years. © Nicole Spaulding / University of Maine
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Thick air: Humans have been polluting air over Europe for at least 2, 000 years with lead and probably also other pollutants. This is confirmed by the analysis of an ice core from the Alps. Contrary to previous assumptions, air pollution started long before the industrial revolution. The only clear break occurred around the year 1350 - when the plague half destroyed Europe.

In addition to "classic" air pollutants such as nitrogen oxides, fine dust or ozone, we also inhale tiny amounts of lead with the air. This heavy metal is considered to be extremely toxic because it can damage even the smallest doses nervous system and disturb the reproduction. Especially in children, creeping poisoning with lead can lead to behavioral disorders and mental deficits.

However, it has not been known as of when the lead contamination of the air is considered increased and where the natural, unaffected lead content of the atmosphere is. One of the reasons why scientists and authorities used lead levels prior to industrialization as a reference value - assuming that there were no lead emissions from humans at that time.

Ice core as lead indicator

Now, Alexander More of Harvard University and his colleagues reveal that this assumption is wrong. For their study, they had taken an ice core from the Colle Gnifetti glacier in the Italian-Swiss border area of ​​the Alps. The 72-meter core supplies ice cream from around 21, 000 years of European history.

The ice core before it is removed from the drill © Nicole Spaulding / University of Maine

With the snow deposited over time and the air contained in it, the ice core has also conserved the atmospheric lead levels of the past 2, 000 years. With the help of laser-based, highly accurate mass spectrometer analyzes, the researchers were able to accurately reconstruct the lead contamination up to the year. display

Dirty for 2, 000 years

The surprising result: "The new data shows that the European air of the last 2, 000 years has been contaminated almost continuously with lead from human activity, " the researchers report. Long before the industrial revolution, the lead levels of the air were measurably increased. Sources of heavy metal was mainly the ore mining, but also the metal processing.

"Our results show that what we considered to be the natural background burden of lead is in fact also of anthropogenic origin - and has been for 2, 000 years, " states More and his colleagues. "This has far-reaching significance for current policy decisions in the environment, industry and public health."

Lead levels of the air in the period from year 1 to 2007 - the slump during the plague pandemic is clearly visible. Alexander More / AGU / GeoHealth

Collapse by the "black death"

Evidence that the measured lead levels actually originate from human activity was provided by the core data for the years 1349 to 1353. During this time, the measured values ​​dropped abruptly to values ​​below the detection limit and thus almost zero. "When we saw the extent of this decline - and only once in the entire 2, 000 years - we were intrigued, " says More.

A look into history reveals the cause of the sudden "lead break": during this time, the plague was rampant in Europe. The "Black Death" raided one third to almost half of the population and brought almost all economic activities to a halt and thus the mining and processing of lead and other heavy metal-containing ores. As a result, the lead contamination of the air dropped to almost zero. There were further, less pronounced sinks in lead levels in 1460, when another epidemic weakened the economy and hence lead demand, and in 1885, due to a severe economic crisis.

True background load is almost zero

The plague pandemic readings show that, despite the presence of lead in the earth's crust, hardly anything is released into the air by nature, the researchers explain. Thus, without human influence, the natural exposure of lead in the air is close to zero and not in the previously considered pristine industrial values.

"The new measurements represent a significant change in our understanding of atmospheric lead exposure, " say the researchers. "Because what was hitherto regarded as a natural background and therefore as harmless to health was not natural. It also contradicts our assumption that preindustrial lead levels had no effect on human health - because they were natural. "(GeoHealth, 2017; doi: 10.1002 / 2017GH000064)

(American Geophysical Union, 01.06.2017 - NPO)