Just outside Ures, a desert town in north-west Mexico, a copse of palo verde trees blooms around a concrete compound. It is unpainted, unfinished and overgrown. Inside, plasterboard walls have crumbled to the floor between scattered mounds of horse manure. But outside, clusters of bright yellow flowers hang around the grey walls like a fine mist.
A decade ago, the seal blew off a pipe at a copper mine 160km (100 miles) north of Ures, and enough acid waste to fill 16 Olympic pools spilled out. Carried by the Sonora River, the orangey brown pollution spread through a dozen towns, home to more than 25,000 people. At the time, people reported diarrhoea and vomiting, headaches, rashes and peeling skin.
Now, cancer cases are on the rise, and tests show that heavy metals from the spill persist in the water, ground, air and blood of almost everyone still living its path.
The building should have been a hospital – the first and only one for miles around – but in 2017 construction stopped. Laura Garcia, a grandmother, now retired from work, hangs her head and walks away. “The plants are pretty, but the unfinished hospital is so very ugly,” she says. “A beautiful lie.”
After the spill at the Buenavista del Cobre mine on 6 August 2014, the owner, Grupo México, created a fund to remediate what Mexican officials now recognise as the worst mining disaster in the country’s history. But many of the fund’s long-term commitments – from dozens of water treatment plants to the hospital – remain unfulfilled.
Grupo México, the country’s fourth-largest conglomerate, says any remaining pollution comes from other sources and that its efforts to remediate the spill are complete. Local people say they have barely started.
“They told us very clearly that in five to 10 years there were going to be diseases, then left us with the start of a hospital,” Garcia says. “They promised us specialist doctors and totally abandoned us.”
At first, people were ignored because there was no immediate increase in disease, says Martha Aguirre, a mother who sells tortillas in Arizpe, one of the larger cities halfway up the valley. “But now it is no longer one among thousands. It’s your mother, your father, your brother, your neighbour or a friend from school.”
Her sister had been fighting breast cancer for two years when doctors found a tumour in her father’s prostate last winter. Studies have linked both types of cancer with exposure to heavy metals contained in the spill.
“Our whole life changed,” Aguirre says. Her children chase a green ball around the floor behind her as the evening light fades. “When we were kids, we would go down to the river to bathe in the middle of the day. Now, if our kids say, ‘Mom, let’s go to the river’, I say, ‘No, my son, it has heavy metals in it.’”
Indoors, Aguirre unfolds test results from the government health department. On one sheet of A4, they quantify the dangerous levels of magnesium, arsenic and lead in her son Jamie’s blood. He will spend the rest of his life with an elevated risk of organ failure, lesions and cancer. “How do you explain that to children?” Aguirre says.
In a study published last summer, Mexico’s environment agency found “alarming” concentrations of heavy metals polluting the water, ground and air across almost 100 sq miles (260 sq km) in the spill’s path. More than half of the region’s drinking wells were found to be unsafe and every soil sample collected contained mercury, a sign of mining pollution and not found naturally in the region.
While different heavy metals affect the human body in different ways, long-term exposure to many of them has been linked to cancer. Cells mutate to metabolise arsenic, for example, which often kickstarts the formation of lung tumours.
Researchers also found fewer insects closer to the Buenavista del Cobre mine. This pollinator die-off could partly explain why many towns along the river say their farms never returned to pre-spill productivity. Another reason could be an open-air waste tank at the mine, which the study suggests should be sealed off.
Grupo México initially blamed the spill on heavy rain before a government investigation revealed cost-cutting construction defects in one of the waste dams. After the spill, the company was fined 23m pesos (£1m) and put an additional 1.2bn pesos (£52m) into a remediation trust fund.
Government officials distributed bottled water and reimbursed locals for lost business. Construction work began on the hospital. A progress report on the first anniversary of the spill promised treatment plants for drinking water in every town along the river and health monitoring for another 15 years.
The trust was closed in 2017. Millions of unspent pesos were returned to Grupo México, and the hospital’s construction stalled. Of the 10 water plants that were started, only two work today, one at the northernmost end of the valley, only accessible by a dirt road.
Rodolfo Tamayo was a civil servant and served as president of the committee charged with administering the fund. “Perhaps I made some mistakes, but in general terms this was the most successful case of remediation in Mexican history,” Tamayo says, adding that the fund spent seven times the region’s GDP before it closed.
“The trust was created for remediation, but that was a limited activity,” he says. “It’s not a development fund to support the community in all the environmental or economic problems they have.”
When he closed the trust, Tamayo says he followed the advice of the government’s sanitary protection commission, a regulatory wing of the health department. The hospital was abandoned, for example, because the commission’s sitting director left to pursue a political career, and his successor, Julio Sánchez y Tépoz, estimated the caseload would be too low to justify the construction.
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Neither Sánchez y Tépoz nor the health department replied to a request for comment.
Tamayo and Grupo México attribute current pollution levels to other sources in the region. The government’s 2023 study explicitly blames the spill, but Tamayo dismisses its findings. “A high-school student could do a better study than that,” he says of the 239-page report.
“There are many mines in the watershed they didn’t sample – historic spills, pollution problems the different municipalities create, pesticides and agrochemicals. It’s like receiving a diagnosis of cancer without having a test, just because you have some symptoms and you saw on Google there are pollution problems.”
Tamayo, who ran environmental policy for the recently defeated presidential candidate Xóchitl Gálvez, says the spill has become a convenient scapegoat for new administrations to avoid responsibility for the region’s wider industrial contamination. “If there is a pollution problem, why don’t they close the mine immediately?” he says.
Grupo México’s US subsidiary Asarco has a history of bankruptcy and is responsible for environmental pollution at 20 “superfund sites” across the US. Since the spill, Grupo México has invested billions of dollars in expanding Buenavista del Cobre.
Without a hospital, many have left the valley: the population of the town closest to the spill has halved since 2014. Francesca Palacio, a single mother and one of Garcia’s neighbours in Ures, moved to the state capital, Hermosillo, so that her eight-year-old son could receive chemotherapy for leukaemia.
Others have decided to forgo treatment. When Mario Salcido, another of Garcia’s neighbours, was diagnosed with leukaemia, he was told that sunlight could mutate his leukaemia cells. Ures is in the desert, and the nearest hospital offering chemotherapy is in Hermosillo, nicknamed City of the Sun. So Salcido declined treatment.
The year leading up to the spill’s 10th anniversary has seen a flurry of stop-start acknowledgment. Two months before the government’s study, Mexico’s human rights commission decried the ongoing pollution crisis as “violations of the right to a healthy environment, safe drinking water and health”.
Then, shortly after the study, the government announced it was pursuing legal action against Grupo México, after which the company wrote back to establish a working group. The environmental department did not say whether it had ever filed a formal lawsuit and did not respond to a request for comment.
In response to the allegations, Grupo Mexico says the incident was promptly reported and resolved, arguing that remediation efforts neutralised the spill’s impact by November of the same year. The company also claims that the remediation recovered the metals from the spill and was recognised by the federal government.
Also, according to Grupo Mexico, the private trust created “as a payment vehicle exercised 1,232.9m pesos, and the company directly applied another 784.3m pesos, giving a total of 2,017.2m pesos.” The company also says that other sources of regional contamination include the natural leaching of minerals, illegal mining and incorrect agricultural practices, adding that it is the target of “disinformation campaigns by groups that distort the facts, lie, and seek to confuse the public and manipulate the population of the area.”
For Aguirre and her neighbours, however, words have lost value, and working groups are cheap. A week after Mexico’s June election, Aguirre and a small group of local people travelled to Mexico City to hand-deliver a note to president-elect, Claudia Sheinbaum.
“Don’t forget the Rio Sonora,” it read. “You have the opportunity to go down in history for making justice a reality.”
In a photograph at the capital, Aguirre is the only one who is not smiling. She admits that hope is fading. “People are tired. Tired of shouting and not being listened to. I am tired of meeting after meeting. You get fed up. Maybe that’s what they want: that we get angry and tired of fighting, and they leave it and wait until we die of cancer.”