The first time a person crunched a frigid foot upon the South Pole was in 1911, when Norway's Roald Amundsen, the so-called "last of the Vikings," made a secret trip to that loneliest of spots with a sled-dog team.
Unbeknownst to Amundsen was that the South Pole had already been touched by humanity. The feverish industrial hustle of the 1800s—all the smelting, mining, and burning of coal—had tainted the ice with significant amounts of poisonous lead.
The legacy of our ancestors' pollution is crystallized in the Antarctic, according to international researchers writing in Scientific Reports. After drilling ice cores on the continent containing material from as far back as 1600, they found giant leaps in lead contamination in the late 19th century. High levels of lead persisted over most of the 20th century save for little dips during the Great Depression and the end of World War II. The heavy-metal foulness dropped in the 1990s, though current levels remain nearly four times as high as those in pre-industrialized times.
The researchers estimate that industrial activity has facilitated the movement of 750 tons of lead to Antarctica over the last 130 years. For context, that's the weight equivalent to a dozen M1 Abrams battle tanks. The toxic spike they measured is illustrated in this graph of lead concentrations over time; blue stands for below-average values, red above:
That "lead pollution at that time was nearly as high as any time ever since, is surprising to say the least," says Joe McConnell, a scientist at Nevada's Desert Research Institute and the study's lead author. So who's to blame for soiling this virgin continent? Part of the responsibility lies with Australia, which opened up two industrial facilities around the time the lead started wafting over the ice. The chemical signature of one of the facilities, a mine in Broken Hill, is present in many of the samples from the late 1800s all the way to the present day.
Though it's not like people are raising kids in Antarctica who might eat the leaden snow—the climate's not that warm... yet—the discovery is a sobering reminder that as a species, we suck at keeping things pristine. Here's McConnell with the final word: "While recent contamination levels are lower, clearly detectable industrial contamination of the Antarctic continent persists today… so we still have a ways to go."