Human pollution of the atmosphere did not begin with the Industrial Revolution of the mid-eighteenth to the mid-nineteenth century, as is often assumed. In fact, lead mining and smelting activities have been polluting the air for at least the past 2,000 years—with one four-year respite—according to a pioneering project that joined researchers in climate science, history, toxicology, and archaeology.
Aided by a new ultra-high-resolution laser mass spectrometer, scientists analyzed, with unprecedented precision, air trapped in a 72-meter-long ice core extracted from the Colle Gnifetti glacier high in the Alps near the Swiss-Italian border. For the first time, atmospheric lead could be charted on a sub-annual basis and could be correlated with known historical events.
The cross-disciplinary team of scientists, led by historian Alexander F. More of Harvard University, noted that the lead level had fluctuated over the centuries with rising and falling economic activity. They found, however, only one period in the past two millennia during which atmospheric lead dropped to an undetectable background level. They pinned that decline to the years 1349 to 1353, when Eurasia was ravaged by the greatest pandemic in recorded history, the Black Death. An estimated 40-50 percent of Europe’s population died during those four years, and economic activity, including virtually all lead mining and smelting, came to a halt.
Authors of this study emphasize that only during the four years of the Black Death did lead drop to an undetectable level. Their findings upend current understanding of the natural level of atmospheric lead, which they estimate to be near zero. Current policies and industry consensus have assumed that it occurs at a significant level and is, therefore, acceptable. These researchers see this assumption as “clearly misleading.” Lead in the environment enters the human body via water, air, soil, food, and other sources, and even very low blood concentrations of lead can have toxic effects, especially in children. Alexander More and his colleagues urge that the “crucial implications” of anthropogenic lead in the atmosphere for public health and environmental policy be reassessed in light of their findings. (GeoHealth)