Soot From the Very Start of the Industrial Revolution Has Been Found at the Top of the Himalayas

Soot dating back to the start of the Industrial Revolution in the eighteenth century has been detected on the world's highest mountains—long before the first climbers ascended their peaks. The findings of a new study, published in PNAS, show the byproducts of burning coal settled on the top of the Himalayas as early as 1780, when the European Industrial Revolution was starting to take off.

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Traces of toxic metals from the late eighteenth century were detected in an ice core sample taken from the Dasuopu glacier on Shishapangma, a mountain located approximately 6,400 miles from London, U.K. The first person to reach Shishapangma, the world's 14th highest mountain, did so in 1964. "Unintended consequences were and are still part of human history," lead author Paolo Gabrielli, from the Byrd Polar and Climate Research Center, Ohio, told Newsweek. "I see irony in the fact that we humans did not learn this lesson and we still believe to have everything under control." Gabrielli and colleagues looked for traces of 23 toxic metals in an ice core sample taken 23,600 feet above sea level—the "highest drilling site on Earth." The core provides a physical record of environmental conditions throughout history. This particular sample contained ice frozen over several centuries, from 1499 to 1992. By sifting for clues, scientists can practically pinpoint the year a layer of ice is formed. The team found above normal levels of various toxic metals in layers as early as 1780. These metals include cadmium, chromium, nickel and zinc—all of which are found in soot (fly ash) produced in the burning of coal. According to the study's authors, the metals would have traveled thousands of miles from Britain to Tibet on winter winds blowing west to east. Some of the metals identified in the sample—zinc in particular—may have been produced by large forest fires, started to clear trees for farms to feed booming populations as countries entered industrialization. The strongest contamination was found in layers frozen between 1810 and 1880, which researchers say could be caused by wetter-than-normal winters. This would have caused more ice and snow to form. In more recent years, the scientists report the presence of another toxic metal found in gasoline: lead. "We found confirmation that the lead content increased in the Himalayan atmosphere during the second part of the 20th century due to its use as an additive in gasoline," said Gabrielli. "However, this glacier shows, in general, a smaller impact than expected from the recent deposition of toxic metals in industrialized parts of the world." Levels of trace metals found in the ice sample are not high enough to be dangerous or toxic, but Gabrielli warns continued exposure could cause toxic levels of these substances to build up in local animals in the future. "The levels of metals we found were higher than what would exist naturally, but were not high enough to be acutely toxic or poisonous," he said in a statement. "However, in the future, bioaccumulation may concentrate metals from meltwater at dangerous toxic levels in the tissues of organisms that live in ecosystems below the glacier." Gabrielli and his team now hope to investigate the nature of these contaminating materials. "It is now important to clarify the nature of the anthropogenic particles that were dispersed in the atmosphere," said Gabrielli. "The chemical characterization of the single particles entrapped in glaciers will be important to understand what the carriers of toxic heavy metals are and what the precise human activities that mainly contribute to these emissions are."