Mercury poisoning is widely considered the single greatest hazard of gold mining, affecting millions of miners and their communities worldwide. Artisanal and small-scale gold mining (ASGM) alone accounts for 37% of the roughly 2,200 tonnes of mercury released into the environment each year, making it the largest source of mercury demand on the planet. But mercury is far from the only danger. Gold mining exposes workers and surrounding ecosystems to a range of physical, chemical, and environmental threats that make it one of the most hazardous industries in existence.
Mercury Exposure: The Biggest Threat
In small-scale and artisanal gold mining, miners mix mercury with gold-bearing sediment to form an amalgam, then burn off the mercury to isolate the gold. This process releases mercury vapor directly into the air miners breathe, and virtually all of the mercury used ends up in the surrounding environment. Air concentrations around amalgam burning sites almost always exceed the World Health Organization’s public exposure limit of 1.0 μg/m³.
Inhaled mercury vapor damages the nervous system, kidneys, lungs, digestive tract, and immune system. At airborne concentrations of just 15 μg/m³, kidney damage and changes in blood enzymes begin to appear. At 30 μg/m³, visible tremors develop. Workers with high chronic exposure show signs of autoimmune dysfunction and systemic inflammation, with elevated levels of inflammatory proteins in their blood compared to miners who don’t work with mercury.
The harm extends well beyond the miners themselves. Mercury converts to methylmercury in waterways, where it accumulates in fish. When pregnant women in mining communities eat contaminated fish, their developing babies face serious neurological risks. Fetal brains are especially vulnerable, and transplacental exposure has been linked to intellectual disability, seizures, vision and hearing loss, delayed development, and language disorders. Children with chronic exposure can develop acrodynia, a painful condition marked by red, swollen hands and feet.
Silica Dust and Diesel Fumes Underground
Underground gold miners face a different set of airborne hazards. Drilling and blasting through rock releases fine crystalline silica dust, which causes silicosis, an irreversible scarring of the lungs. This has been a known killer in gold mining for over a century and remains a serious occupational risk today.
Diesel-powered equipment compounds the problem. The International Agency for Research on Cancer classifies diesel particulate matter as a Group 1 human carcinogen, the highest risk category. These tiny particles have a large surface area that absorbs additional toxic compounds, including cancer-causing polyaromatic hydrocarbons. Short-term exposure causes headaches and irritation of the eyes, nose, and throat. Long-term exposure raises the risk of cardiovascular disease, and diesel particulates have documented toxic effects on the lungs, heart, kidneys, brain, liver, and placenta.
Rockbursts and Tunnel Collapses
Deep underground gold mines, particularly those in South Africa that reach depths of 3 to 4 kilometers, face a uniquely violent physical hazard called a rockburst. When natural stress in surrounding rock approaches the breaking strength of the stone, the sudden release of stored energy can violently eject chunks of rock from tunnel walls with explosive force. Two conditions drive these events: extremely high natural stress at depth and brittle, hard rock that fractures suddenly rather than deforming gradually. Excavation itself can trigger the final release.
Even in modern operations, fatalities persist. Among the world’s largest gold producers, fatality rates in 2024 ranged from 0.013 to 0.050 per million hours worked. Gold Fields, which operates some of the world’s deepest mines, recorded the highest fatality rate at 0.050 and a total recordable injury rate of 2.62 per million hours worked.
Vibration Injuries From Rock Drills
Miners who operate pneumatic rock drills for years develop a condition called hand-arm vibration syndrome. The drills used in gold mining can produce vibration levels up to 31 m/s², and about 15% of vibration-exposed gold miners in South Africa have been diagnosed with the condition. Symptoms include tingling, numbness, loss of grip strength, and pain. The average time from first exposure to symptom onset is about 5.6 years. Loss of dexterity makes everyday tasks difficult and raises the risk of workplace accidents.
Acid Mine Drainage
Gold ore frequently contains iron sulfide minerals like pyrite. When mining exposes these minerals to air and water, a chain of chemical reactions produces sulfuric acid. Bacteria that thrive in acidic conditions accelerate the process, creating a self-reinforcing cycle that can continue for decades or even centuries after a mine closes.
Water draining from active and abandoned gold mines routinely reaches pH levels between 2.5 and 3.5, roughly as acidic as vinegar or stomach acid. At the Berkeley Pit, a former copper and gold mine in Montana, water fills a massive open pit at pH levels between 2.5 and 3.3. This acidic water dissolves heavy metals from surrounding rock, carrying arsenic, cadmium, lead, and other toxins into streams and groundwater. Recovery is slow. Measurements at one site showed water with a pH of 2.37 near the source of contamination and near-neutral pH only 4,000 feet downstream, illustrating how concentrated the damage can be.
Tailings Dam Failures
After gold is extracted, the leftover slurry of ground rock, water, and processing chemicals is stored behind earthen dams called tailings dams. These structures must hold back enormous volumes of toxic material indefinitely, and when they fail, the results are catastrophic. In September 2022, a tailings dam at Jagersfontein, South Africa, released more than 6 million cubic meters of liquid sludge in an uncontrolled flood. The wall of mud buried nearly 200 homes and smothered roughly 1,600 hectares of farmland and grazing land. Two people died and one was never found.
Tailings dam failures are not rare events. They represent a persistent structural risk across the industry because the dams must be maintained long after mining ends, and older dams were often built to less rigorous standards.
Water Consumption
Gold mining is extraordinarily water-intensive. A case study in Colombia measured the water footprint at roughly 80 cubic meters of freshwater per kilogram of gold extracted. Since a kilogram contains just over 32 troy ounces, that works out to about 2,500 liters (660 gallons) per single ounce of gold. In arid regions or areas where communities depend on the same water sources, this level of consumption creates direct competition for a finite resource and can lower water tables for surrounding populations.
Cyanide in Industrial Operations
Large-scale gold mines use cyanide solutions to dissolve gold from crushed ore, a process called heap leaching or tank leaching. While industrial operations manage cyanide more carefully than artisanal miners manage mercury, spills and leaks remain a persistent environmental risk. Cyanide is acutely toxic to aquatic life, and contaminated water from processing facilities can reach rivers and groundwater through liner failures, overflow events, or improper disposal. The combination of cyanide, acid drainage, and heavy metals makes the environmental footprint of a single large gold mine potentially enormous and long-lasting.