Illegal mercury mining in Mexico surges as gold demand fuels contamination in Sierra Gorda

A spike in global gold prices has triggered a surge in artisanal mercury mining in Mexico’s Sierra Gorda region, local residents and researchers say, exposing miners and nearby communities to dangerous contamination and sending large quantities of the toxic metal to illegal gold operations across the Amazon.

Miners follow veins of cinnabar, the red ore that carries mercury, through narrow tunnels and heat crushed rock in wood-fired ovens to release mercury vapors that condense into liquid in improvised collectors. The metal sells for more than ten times its price a decade ago, making mining a lucrative — and hazardous — livelihood in impoverished towns such as San Joaquin in the central state of Querétaro.

Research and on-the-ground reporting show the boom has deep local and international consequences. Mexico is estimated by the United Nations to be the world’s second-largest producer of mercury after China, yielding about 200 tons a year. The price of mercury in towns like San Joaquin rose from roughly $20 per kilogram in 2011 to between $240 and $350 per kilogram in recent years, according to residents and researchers. Small bottles filled with freshly refined mercury now fetch prices equivalent to about $1,800 on local markets, and traffickers purchase the metal for resale to buyers in Peru, Bolivia and Colombia.

Health researchers say miners and their families show signs of chronic mercury poisoning, including tremors, neurological decline, vision and hearing loss, and developmental delays in children. Fernando Díaz-Barriga, a toxicologist who has studied mercury mining in central Mexico for years, said scientists have documented dangerously high mercury levels in workers, soil, sediment and vegetation near mining sites.

"This region isn’t just polluted. It’s poisoned," Díaz-Barriga said, describing the area around some mines as among the most contaminated in Mexico.

Miners described daily exposure. They dig deep into mountains, haul bags of ore to the surface, burn rock in ovens and inhale fumes as mercury vaporizes. Waste rock is often dumped into nearby stream beds and can be carried downstream during rains to feed into larger watersheds. Some miners said they cook mercury in ovens installed in their homes during the rainy season. A lawyer and researcher who has worked with miners for more than a decade said her own blood tests showed mercury levels 12 times normal, and she suffers from brain inflammation, hearing loss in one ear, tremors and depression.

The mercury produced in Sierra Gorda and other Mexican mining communities is widely trafficked into South America, where it is used to extract gold from river sediments in illegal mining operations. Environmental investigators and law enforcement have documented the shipment of mercury concealed with other materials; in July, Peruvian authorities seized a shipment of four tons of mercury hidden in bags of gravel, a haul valued at roughly $500,000.

The international context is complex. A 2017 United Nations treaty, the Minamata Convention, seeks to curtail mercury mining and trade because of its health and environmental impacts, and Mexico was among the countries that signed it. The treaty calls for the phase-out of primary mercury mining and restricts trade. But researchers and miners say the global reduction of legal mercury supply has driven up prices and demand for artisanal sources, creating incentives to expand extraction and trafficking.

Local leaders and miners argue that mining is a long-standing way of life and a critical source of income in a region where nearly half of residents live in poverty. Hugo Flores, a miner in his late 30s who returned from the United States after being denied a green card, said mining now attracts younger people who once sought work abroad. "For the first time in their lives, mercury is worth something, and the miners are saying: 'It's worth poisoning myself if I'm going to earn something,'" said Fernando Díaz-Barriga, summarizing miners' calculations.

Government efforts to ease the transition away from mercury mining have been slow to reach communities. Mexico and the U.N. established a fund in 2021 intended to provide workers with training and resources for alternative livelihoods, but miners say they have seen little benefit. Mexico’s environment agency said it has conducted initial studies for programs designed to transition miners away from mercury and is working to combat illegal trafficking, but it declined to comment on accusations that it had failed to assist miners. The U.N. Environment Programme acknowledged delays in implementation tied to security risks in some mining areas and said authorities are working to accelerate support.

Environmentalists warn that continued mining could inflict long-term damage on the Sierra Gorda Biosphere Reserve, a biodiversity hotspot that includes high-altitude forests and jungle home to species such as jaguars, military macaws and Mexican black bears. Scientists said contamination of soil, trees and waterways could have cascading effects on ecosystems and human health that may take years to fully emerge.

The miners themselves expressed fears that restricting the trade in mercury without providing viable economic alternatives could push extraction further underground and create openings for criminal groups. Some local officials and watchdog reports have pointed to growing interest from organized crime in controlling mineral trafficking, though miners and community leaders warned that suggesting cartel involvement can stigmatize and criminalize vulnerable workers.

María Izarelly Rosillo, a researcher based at the Autonomous University of Querétaro who has worked closely with miners for 12 years, estimated roughly 3,000 people in the region depend on mining or recycled materials from mining for their livelihoods. She said the economic gains have brought development but at a substantial cost in health and environmental damage.

The United Nations and environmental advocates say reducing global mercury consumption, enforcing existing trade restrictions and investing in economic alternatives for mining communities are necessary steps to curb both local poisoning and the flow of mercury to illegal gold operations in the Amazon. For miners in Sierra Gorda, the immediate calculus remains driven by poverty and price: the metal that has fed generations of workers now commands enough value that many are willing to accept its risks to support their families.

Authorities face a difficult policy trade-off between enforcing bans that may drive the trade underground and providing timely, practical alternatives that match miners' earnings while mitigating environmental and health harms. Until effective transitions and enforcement converge, experts warn the mercury boom is likely to continue fueling contamination across Mexico and into South America, with consequences for ecosystem and human health that could persist for decades.