Chemists challenged to help curb mercury poisoning

Mercury poisoning through artisanal and small-scale gold mining is increasing — but Flinders University scientist Dr Justin Chalker believes that chemists can provide cheap and effective solutions to curb the damage.

More than 15 million people use mercury to mine for gold in about 70 countries, representing up to 25% of the world’s gold production. The process involves using liquid mercury to form an amalgam as it extracts fine traces of gold from ore. The resulting mercury–gold amalgam is then heated to boil off the mercury from the gold, but the subsequent release of mercury from vapours and tailings exceeds 1000 tonnes each year — accounting for 37% of global mercury emissions.

Health effects on mining communities are dire, with inhaled mercury leading to neurological damage, kidney damage and other critical health issues — while mercury contamination of water and soil affects foods. Yet gold mining by these dangerous methods is on the rise, particularly in poor and remote areas of Asia, Africa and South America, where it forms the backbone of an informal economy that operates without licences or legal authorisation.

Dr Chalker said the answer is not banning mercury use in gold mining — which can’t be effectively policed — but to instead develop and promote new mercury-free strategies for mining, tailings processing and remediating damaged environments. He believes chemistry is the key to this solution and that novel, inexpensive innovations are necessary, as resources are scarce in poor communities that favour mercury-dependent gold mining.

His team at Flinders is now taking a decisive lead on the matter, having created a polymer made from waste canola oil and sulfur (a low-cost by-product from petroleum production) that can extract mercury from polluted soil, water and air. After successful field trials in December 2017, Dr Chalker is excited by the prospect of its widespread application.

“Chemists can play a central role in solving these mercury problems,” said Dr Chalker. “Introducing portable and low-cost mercury sensors, inexpensive and scalable remediation technologies, novel methods to prevent mercury uptake in fish and food crops, and efficient and easy-to-use mercury-free mining techniques are all ways in which the chemistry community can help.”

Dr Chalker emphasised that new technologies and techniques should be low-cost and adaptable to the remote and under-resourced areas in which mercury-dependent gold mining is most common.

“We have to be clever to find effective solutions that can change a tragic and delicate situation,” he said. “Chemists are in a position to help solve the mercury problem in gold mining, and we need to take action now.”

A review outlining these concerns and voicing a call to action, written by Dr Chalker in collaboration with Dr Louisa Esdaile, has been published in Chemistry, A European Journal.

Image caption: After the liquid mercury reacts with gold, it forms an amalgam that has the consistency of paste. These amalgams are typically 40–80% mercury. The amalgams are combined by hand and the excess mercury is recovered by squeezing the amalgam in a porous cloth. The remaining amalgam is then burned directly with a torch or over a stove to vaporise the mercury and isolate the gold. Image credit: Yayasan Tambuhak Sinta (YTS) and Pure Earth.