How mercury poisons miners and enters the food chain


The majority of Zimbabweans working in gold mines are employed by unlicensed companies run by individuals.


A huge muscular man with a pulpy face is busy working on gold ore in a pan, wiping rivulets of sweat off is face with the back of his hand as the summer heat mercilessly baked the earth.

Now and again, he empties the grey coloured water from the giant pan into a makeshift drain and on into a stream nearby.

Vast herds of cattle gather around to drink from the greyish water, oblivious of the danger posed by the mercury which taints it.

In this area, fortune is made with a chisel, a pan, mercury and lots of good luck.

A 19th century-style gold rush has brought fortune-seekers, hard workers and dreamers to Mhondoro, transforming the normally idyllic environ into a labyrinth of activity as gold panners tear through verdant forests in search for the precious mineral.

Men, women and children all wade into the area, digging indiscriminately for that little gold vein that can transform their lives in an instant.

About 60% of the country’s gold is produced by artisanal and small-scale miners, most of whom use mercury to extract it from the earth.

The industry is a safety net which supports hundreds of thousands of people, but the miners risk poisoning themselves, their children, the land and everyone else.

Mercy Mutedzwa, a woman in her early 40s, is not feeling well.

She has been part of a smaller group operating within the Jongwe small-scale gold mining association in Mhondoro district.

“I often have a headache and I am weak. I have a bitter taste in my mouth,” she explains.

At a hospital where she recently sought treatment, she said, doctors told her she is being slowly poisoned by mercury, but she has no plans to quit anytime soon.

Mutedzwa has been working with mercury for eight years and now she is showing typical symptoms of mercury intoxication.

But, unemployed and lacking other alternative sources of income, she has always returned to the area.

“If I stop, my two children will not go to school,” she said.

The muscular gold panner, Temba Manika, says he has been told about all the dangers of mercury but has always used it in the 15 years that he went into small-scale gold mining.

He has also personally experienced its health hazards.

“It affects your skin and eyes, but because it’s our only means of earning a living, we have to endure. We have to earn a living. We hope an alternative means is availed so that we can work better,” he said.

Although mercury use in small-scale gold mining in Zimbabwe is illegal, miners still use it to extract gold from the rock or soil.

Miners excavate and crush large quantities of earth or rock containing a small quantity of gold.

When mercury is mixed with the slurry, it amalgamates with the gold and the amalgam sinks to the bottom.

The amalgam is separated out, some excess mercury is removed, and the rest is boiled off.

A ton of ore may contain less than an ounce (28 grammes) of gold.

What remains is then taken for smelting, where the mercury evaporates in the heat, leaving the gold behind. But the fumes are highly toxic, which is why smelters like Tapson Musiwaro often show more severe signs of mercury poisoning than miners who use it in the field.

“Mercury is a neuro-toxin,” explains Kadoma-based medical doctor, Anesu Kusangaya who has attended to many victims of mercury poisoning.

“It affects the cerebellum, which is the part of the brain that helps you move properly, and co-ordinate your movements. Mercury also harms the kidneys and other organs, but the neurological damage it does is irreversible,” he said.

While mercury poisoning appears to be a distant phenomenon to those not directly involved in gold extraction, scientists have recently discovered that in any country with unregulated gold mining such as Zimbabwe, it affects everyone.

For instance, as in the case at Jongwe mining consortium, livestock like cattle and goats could be affected when they drink the mercury-tainted water.

The mercury settles in their body parts which may ultimately make their way on dinner tables in even the affluent homes located far away from the mines.

Mercury is a persistent pollutant as it does not break down in the environment and is transferable through food.

Symptoms of mercury poisoning first appeared in the Japanese fishing village of Minamata. At first, nobody could explain why people began to slur their speech, or stumbled when they walked. They would have trouble swallowing, or tremble uncontrollably. Children were born with disabilities. Thousands would die with what became known as Minamata Disease.

But it took 30 years to identify the cause of the suffering: a local plastics factory that was dumping mercury into the bay. The mercury was contaminating fish, the staple food of the local population, just as it is contaminating livestock whose meat is consumed in most urban households in Harare today.

The discovery led to a series of researches and programmes for action which culminated in what came to be known as Minamata Convnetion.

The Minamata Convention, which came into being in 2013, is an international treaty designed to protect human health and the environment from the human-induced emissions and releases of mercury in an efficient and effective way as part of the gradual move towards elimination of the deadly substance.

Worryingly however, Zimbabwe is one of the few countries in the world which have not ratified the convention and as such, it has no legal framework for prevention of its abuse.

In terms of the Zimbabwean constitution, international laws can only come into legal effect when they have been ratified by parliament.

The Environmental Management Agency (EMA) is currently spearheading the ratification process, which is sadly taking too long.

“We are conducting a number of projects to establish the quantity of mercury that is emitted and released in the country in a bid to inform policy and stakeholders prior to ratification. Therefore the nation will ratify the convention when all structures that will enable Zimbabwe to fully comply with the provisions of the convention are in place,” EMA spokesperson Joyce Chapungu said.

“Once ratified, the convention will be a reference point on the legislation to tackle the problem of controlling the use and influx of into the country and prevent the possibility of Zimbabwe being a dumping ground of such hazardous substances,” she added.

Artisanal small-scale gold mining is the largest source of mercury pollution in the world after the burning of fossil fuels.

There are no large nuggets of gold to be mined around Mhondoro; only tiny particles of the precious metal are present in tons of earth.

In other areas, its potential for harm is multiplied because it is being used in conjunction with cyanide.

“Together mercury and cyanide create double the problem in the environment,” Chapungu said.

Cyanide helps to dissolve the mercury, and when the waste is spilled into paddy fields it binds with organic molecules in the environment, becoming methyl mercury. This is far more toxic.

In Minamata it was methyl mercury that poisoned thousands of people.

The modern-day gold rush is thus leaving behind a toxic legacy of mercury pollution that will continue to be a problem for some time.