During the Mongol period in China (1271−1368 AD), lead pollution due to silver smelting in the Yunnan region exceeded contamination levels from modern mining activities by nearly four times.
Selama periode Mongol di China (1271-1368 M), polusi timbal akibat peleburan perak di wilayah Yunnan melampaui tingkat kontaminasi dari kegiatan penambangan modern hampir empat kali.