Paracale in the Philippines has a long gold mining tradition. The pretty coastal town’s emblem features a shovel, pickaxe and miner’s helmet.
It is estimated that four-fifths of Paracale’s residents rely on gold mining. Miners gather ore from riverbeds, mines and even metres-deep pools of mud. Many mix it with mercury, which bonds to any gold particles lodged in the ore. When the mixture is heated, the mercury evaporates and leaves gold behind.
The process releases large quantities of mercury into the atmosphere. Rain and rivers also carry this toxic, heavy metallic element into the ocean, where it can spread further.
Mercury levels in Mambulao Bay, near Paracale, are extremely high. This poses health risks to local people, specifically their central nervous systems. The mercury levels detected in one fish sample in 2017 breached the food safety standards of multiple nations. Reckoning with these impacts, some miners have since abandoned the conventional practice of using mercury.
Though mercury emissions have fallen in the Global North and China, overall they have continued to rise globally, researchers have found. The largest sectoral contribution to this concerning growth is no longer being made by coal combustion, but by gold mining in the Global South.
Mercury moves south
Scientists recently published a study into mercury pollution in the northern hemisphere based on their studies of flowers growing at Mount Everest. Levels in 2020 were 70% lower than those in 2000, they found.
But the global picture is far less rosy. Liu Maodian, a researcher at Peking University’s College of Urban and Environmental Sciences, helped produce a dataset that shows anthropogenic mercury emissions increased by 330% between 1960 and 2021.
Liu says emissions hotspots have shifted south. Mercury pollution in the European Union and US was brought under control in the 1980s and 1990s. The past decade has seen China slash its emissions, though it remains the largest single-nation source. But over the same period, emissions have risen in emerging industrial economies in Southeast Asia, South Asia and Latin America. This has completely offset reductions elsewhere.
The researchers’ calculations found that in 2021, the Global South excluding China accounted for two-thirds of all mercury emissions. Southeast Asia’s contribution is particularly prominent, with emissions having risen there by 700% over the past 62 years.
The cost of gold mining
Artisanal and small scale gold mining has been driven by the price of gold, which has increased by almost 500% in the past decade. Now such mining accounts for 15-20% of gold production globally.
In economically marginalised places like Paracale, gold mining is seen as a reliable livelihood, says Abigail Ocate. She represents the Philippines in her role as a national project manager at planetGOLD, a project funded by the Global Environmental Facility.
Mercury is not necessary for these small-scale operations but it is easy to access and use, and cheap. Sometimes, middlemen who buy the gold provide it at a low cost. So, mercury use continues, even in places where it is illegal – like the Philippines.
Of course, other growth areas are driving mercury pollution, too. These include coal power generation in the Philippines, Indonesia, Vietnam and India, nickel mining, improper urban waste incineration, and skin lightening products that contain mercury.
In “gold towns”, mining threatens water quality, fishing and farming. Ocate tells Dialogue Earth that an environmental and health assessment carried out by her team in Paracale discovered raised levels of mercury in samples taken from local wildlife, residents and miners.
The harm mercury does to the human body is not yet fully recognised. Ocate says that in small-scale mining areas, symptoms of mercury poisoning such as tremors, memory problems and headaches are often misdiagnosed or attributed to ageing.
Mercury in the ocean and seafood
The element is particularly dangerous when it reaches the ocean. Most mercury found in the human body comes from eating contaminated seafood.
Mercury in the ocean comes, in turn, from precipitation, rivers and particulates in the atmosphere. The metal can travel surprisingly far in the atmosphere. Research into mercury levels in zooplankton found that emissions from the coast of Asia, mostly airborne at first, could have an impact in the central Pacific Ocean.
Bacteria convert inorganic mercury compounds in seawater into a more toxic form: methylmercury. This then accumulates up through the marine food chain, beginning with phytoplankton and tiny organisms. As it moves upward to carnivores such as sardines, the concentration intensifies, reaching its peak in top-tier predatory fish, such as tuna.
In non-human animals, exposure to mercury can result in a loss of fertility and mobility. In humans, long-term consumption can damage the central nervous system when the element crosses the blood-brain barrier.
Assessing mercury risks should be led by widespread and credible testing by governmentWang Wenxiong, City University of Hong Kong professor
Fish consumption is on the rise globally. As people in Asia eat more fish on average than those elsewhere, they are more vulnerable to rising mercury pollution.
Wang Wenxiong, a professor at the City University of Hong Kong’s School of Energy and Environment, says mercury movements are complex; mercury levels in seafood are not always linked to local emissions.
China offers a good example. Despite being the biggest emitter of mercury, China’s “fish has basically never breached standards, with very low levels … it’s a strange thing”, he says.
Research by Wang and his team found that overfishing off China’s coast has eroded the food chain, reducing the number of larger predators and leaving mostly smaller fish. This prevents mercury from accumulating upwards. Also, eutrophication (a process in which nutrient buildup, often from agricultural fertiliser runoff, fuels excessive algae growth) has interfered with the bioaccumulation of methylmercury.
Wang says consumers need not worry about mercury in Chinese seafood. However, fish from more distant and apparently “clean” waters may contain much more mercury. Testing, therefore, should focus on the more expensive imported fish. Wang says: “Assessing mercury risks should be led by widespread and credible testing by government.”
As China’s environmental management improves, there is less overfishing and eutrophication. For this reason, Wang warns, the authorities should keep a close eye on mercury levels.
Stronger policy guidance needed in the Global South
Liu Maodian thinks scientists and policymakers need to take the rise in mercury pollution, and the shift in sources to the south, seriously. Monitoring and data collection are essential parts of tackling the problem, but this work is not being done in developing nations.
Abigail Ocate says the Philippines does not yet monitor mercury levels in all its waters, just those near some mining areas. Scientific studies across Southeast Asia are also relatively limited compared to those in East Asia, with most of them overlooking the methylmercury that accumulates in seafood.
Alongside more monitoring, Ocate thinks governments should keep track of human exposure to mercury – and guide their societies towards a healthy and mercury-free future.
