A study of ice caps in the Andes Mountains of South America shows that air pollution is not strictly a modern problem, researchers find.
An ice cap in the Peruvian Andes has been found to contain residue from relentless clouds of metallic dust spewed from silver mines in the 16th century as Spanish conquistadores satisfied their greed for treasure, the researchers say.
Thousands of native people were forced into slave labor to work the mountaintop mines of Potosí in Bolivia, the richest silver source on the globe, where harsh conditions claimed many lives, they report in the journal Proceedings of the National Academy of Sciences.
While the Incas had long extracted silver from the region, the Spanish introduced new processing methods that pulverized silver ore into a powder containing both silver and lead which then was mixed with mercury.
The lead in the powder and the mercury, which evaporated during the silver extraction process involving heating, escaped into the atmosphere, settling into the Quelccaya Ice Cap in the Andes Mountains in southern Peru some 500 miles from the Potosí mines.
The pollutants found in ice cores taken from an altitude of around 18,000 feet are the first clear evidence of man-made air pollution in South America from a time before the Industrial Revolution, the researchers say.
The pollutants found there are strong evidence of "the sad conditions and fate of tens of thousands of locals exploited in the silver mining operations during the colonial period," says study author Paolo Gabrielli, a research scientist at the Byrd Polar and Climate Research Center at Ohio State University.
They also show that pollution continued until the early 1800s, when mining activity fell during the Latin American Wars of Independence, the researchers said.
"Until now, what we knew about pre-industrial atmospheric pollution was limited to the Northern Hemisphere," Gabrielli says.
Many scientists believe human activity has altered the Earth so much that we are now living in a new geological era dubbed the Anthropocene.
When the era could be said to have started is the subject of much debate, but the current findings from South America suggest a much earlier start date than previously thought must be considered, experts say.
"Clearly, colonial Spanish American mining was industrial in scale, and the belief that a dramatic man-made impact on the environment only began in the 18th century is a Euro-centric construct," says Kendall Brown, a history professor at Brigham Young University in Utah, who was not involved in the study.
