It can build up in fish and be passed on to humans, causing serious illness and birth defects.
In Minamata in Japan, methlymercury dumped in industrial wastewater by a factory over decades poisoned tens of thousands of people, around 2,000 of whom have since died.
Sulaiman said the impact of mercury on wider communities was likely to be more serious than on the miners themselves.
“Communities that live downstream and eat fish are at high risk of developing mercury poisoning over the years,” she said.
Gold mining is also wreaking environmental devastation, adding to the destruction caused to the country’s rainforests by industries such as palm oil.
The damage is so widespread around Kereng Pangi that satellite photographs show the area as a huge white blotch amid lush rainforest on Borneo, a vast, biodiverse island shared between Indonesia, Malaysia and Brunei.
Gold mining has also crept into “protected” areas such as Tanjung Puting national park on Borneo, home to a large population of endangered orangutans.
A local official, speaking anonymously, said men were paying off park officials to mine gold in the park. An AFP reporter saw mining equipment lying inside the boundaries on wide stretches of deforested land.
No national program is in place across Indonesia — a sprawling archipelago of more than 17,000 islands where power is heavily decentralized — to convince small-scale gold miners not to use mercury.
But Rasio Ridho Sani, deputy environment minister, insisted the government had sought to encourage miners to use alternative methods.
The Minamata Convention on Mercury would help tighten up the distribution of the metal in Indonesia, where it is not produced, he said. “We hope that we will be able to reduce illegal imports into Indonesia.”
Critics say the treaty lacks teeth as it only commits governments to reduce use of the metal, and does not demand an outright ban on the practice.
Experts in Indonesia were skeptical the treaty would make much difference in a country where gold mining with mercury is supposed to be illegal but continues regardless.
“Even if the agreement were stronger, it wouldn’t really change anything on the ground here in Indonesia,” said Sukoso, director of research institute the Indonesia Society of Water and Aquatic Environment, who like many Indonesians goes by one name.
“It’s already illegal but very difficult to control.”
He said education was the key to persuading miners to stop using mercury.
“The government could do more to inform the miners about mercury, because they’ve been using it for a long time and many don’t understand the dangers.”