Call it the mystery of the white bags. After they were found to be sprawling across acres of land near the Mexican city of Monterrey, authorities ordered their “urgent” removal. Now visual evidence suggests the problem is more extensive than previously known.
An investigation by the Guardian and Quinto Elemento Lab first identified the bags in January, piling up around a factory that recycles toxic waste imported from the US. Based on this finding, Mexican authorities demanded a cleanup of what they said was 30,000 tons of stored material with “hazardous characteristics”.
But aerial and Google Street View photography shows there is at least one more outdoor site related to the company where hundreds more of the white supersacks, typically used to hold industrial chemicals, appear to have been stored. Mexico’s environmental enforcement agency said it would conduct an inspection.
The issue of imported US toxic waste – and related concerns, such as the white bags – have become a lightning rod in Mexico and Canada in recent months, with commentators questioning why they should take the US’s discards as their countries face a new trade war instigated by the Trump administration.
In Mexico, attention has focused on the Monterrey-area factory, which is owned by a company called Zinc Nacional and recycles toxic dust sent to the country by the US steel industry.
According to the latest imagery, the company has now cleared all the bags located there following the order from regulators.
But new photography shows that the bags also cover more than an acre of land 15km (9 miles) away at the plant of a company called Meremex. Business records show that it is majority-owned by Zinc Nacional and has also been licensed to recycle hazardous waste.
Photographs taken on Wednesday by drone, in a collaboration between the Monterrey newspaper El Norte, the Guardian and Quinto Elemento Lab, show that the giant bags remain stacked around the Meremex industrial yard, with blue tarps partially covering them.
Historical Google Earth and Street View photographs show that two more yards in the same industrial park were previously filled with bags that have been cleared over the last two years. They appear similar to the bags in the Meremex yard, and bags on a truck parked in front of one yard read “Made in Mexico by Zinc Nacional”.
Imagery of these bags from 2022 shows that they were, in places, stacked three bags high and that some of them were broken open and spilling powders on to the bare ground. That site is 600 meters (1,969ft) from a river.
Mexico’s environmental enforcement agency, known as Profepa, said it would inspect the sites, saying: “We will also examine the type of material stored to decide whether soil sampling is required and whether remediation is necessary.”
At Zinc Nacional’s plant, authorities initially gave the company 15 days to move bags spread across a 20-acre (8-hectare) industrial scrapyard. Satellite imagery suggests the company was still working to remove bags as recently as 14 March, and drone imagery indicates this yard has now been cleared.
Profepa says the company has told it that these bags contain zinc oxide, a final product that is extracted from the toxic waste and used in products such as rubber and fertilizer. Profepa says the material in the bags has “hazardous characteristics”.
The agency ordered the company to sample the underlying soil and develop a remediation plan for any contamination.
“The sacks are being placed in storage areas with reinforced concrete floors, walls, and steel sheet roofing,” said a statement from regulators at Profepa. It added that the environmental investigation was ongoing and that authorities were also reviewing the licenses of other companies that handle hazardous waste in the state of Nuevo León.
The findings follow an investigation by the Guardian and Quinto Elemento Lab, a Mexican investigative journalism unit, that revealed that the United States exports about 760,000 tons a year of its hazardous waste to Mexico – a practice that environmentalists say raises the danger that the toxic material will not be handled as safely as would be required in the US.
In Mexico, Zinc Nacional is one of the largest importers of US toxic waste, and recycles contaminated metal dust sent to the country by major US steel companies in order to recover zinc.
Toxicologist Martín Soto Jiménez, from the National Autonomous University of Mexico, conducted sampling in the neighborhood around the zinc plant and found high levels of lead, cadmium and arsenic in soil samples – including inside some homes and schools.
In response to questions from reporters, the company said it was working with local and federal authorities and was responding to points raised in inspections.
“We have successfully completed the removal of 100% of zinc oxide material from our operation yards,” it said.
It said Meremex had been shut down in 2023, and that “we will complete the removal of its inventory in the next weeks”.
In addition, the company said it had “serious concerns about both the methodology rigor and reliability of the study” by Soto Jiménez, and about the way it had been reported. It suggested that not enough sites had been tested for contaminants, that the resulting story selectively highlighted only the worst results, that many of the results had not been “alarming”, as the story said, and that the study had been inconclusive as to whether heavy metals found in the samples had originated in the company’s factory.
After the original story was published, state and federal regulators began immediate investigations of the Zinc Nacional plant. Regulators said they shut down 15 unauthorized pieces of equipment at the plant, in addition to ordering the materials stored in the scrapyard moved.
Environmental experts said it is troubling to see so much chemical material accumulating around the property of a plant that is handling hazardous wastes.
“The volume itself is concerning,” said James Rybarczyk, a retired chemistry professor, who once served as an emergency responder to incidents involving chemical hazards in the US. “That’s an enormous quantity of anything – and to just be sitting there?”
Rybarczyk, who has been looking into the activities of Zinc Nacional since the company proposed opening a plant in his home town of Muncie, Indiana, five years ago, said that such supersacks can easily leach chemicals or metals into the soil.
“Where could all this volume come from?” he said. “Why isn’t it being sold? Why is it being stored? Those are my questions.”
Other experts said that places where the bags have been stored require further work to make sure no chemical hazards remain.
Javier Castro Larragoitia, a research professor of environmental geochemistry at the Autonomous University of San Luis Potosí, said sampling would be needed to know the most appropriate next steps.
“If there is a contaminant in the soil, there is always the potential for it to move downward into the subsoil and eventually reach the underground water table,” he said.
The three sites in the industrial park where Meremex is located are in the watershed of the Pesquería River, which flows into the Rio Grande.
Zinc Nacional’s plant is also near an important watershed, according to Mexican environmental attorney Francisco Javier Camarena Juárez. This, he said, “requires stricter oversight of the situation”.
The company said it hired a firm approved by regulators to determine whether there had been contamination from the white bags.
But relying on companies to hire their own investigators could be considered a conflict of interest, said Gonzalo García Vargas, a toxicologist at Juárez University.
“The community could organize and demand that the study be conducted by independent institutions, possibly a public university,” he said. “That’s what was done in Torreón,” he added, referring to contamination around a notorious lead smelter in that city in northern Mexico.
