Hotline well remembers studying Coleridge’s famous poem Kubla Khan in English Literature lessons as a child, even going so far as to be able to recite the entire first stanza.

In Xanadu did Kubla Khan
A stately pleasure-dome decree:
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.
So twice five miles of fertile ground
With walls and towers were girdled round;
And there were gardens bright with sinuous rills,
Where blossomed many an incense-bearing tree;
And here were forests ancient as the hills,
Enfolding sunny spots of greenery.

However, what was not made clear to Hotline by his schoolmaster was that, while the pleasure dome may well have been stately, the picture painted by Coleridge of the surrounding area leaves much to be desired.

Instead of fertile ground and blossoming trees, there was heavy metal pollution and smog.

And, while the river Alph may well have been sacred, it is likely to have contained concentrations of lead high enough to harm aquatic life.

The silver and copper mining activities of the Mongol dynasty caused three to four times more pollution than mining does in the Yunnan area of China today, according to a study published recently in the journal Environmental Science & Technology.

From geochemical analysis on dated sediment cores, the researchers found levels of heavy metals increased over the period, which included lead, silver, zinc and cadmium from atmospheric emissions associated with silver smelting and copper mining.

“Culminating during the rule of the Mongols, known as the Yuan Dynasty (1271–1368 AD), these metal concentrations approach levels three to four times higher than those from industrialised mining activity occurring within the catchment today,” the abstract reads.

“The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern day sediment quality,” it continues.

So, while Genghis Khan’s grandson left his mark on history by being the first foreigner to conquer and rule China, enriching cultural diversity and expanding trade across the Asian continent (much like the HKEx-LMe link up – Ed), he also very much left a physical mark that still affects the people of Yunnan province to this day.