Across Mexico, drinking water is being poisoned


The uncontrolled extraction of water is making the wells a risk by intensifying the release of arsenic and fluoride into the liquid of millions of Mexicans. The analysis of a Conagua database reveals that what was a problem concentrated in La Laguna, is expanding throughout the country. The government knows it, but does not act.

“Your daughter is too young to be urinating arsenic,” a doctor told Claudia González, a community member from San Juan de Los Planes, a town half an hour from La Paz, Baja California Sur. It was 2012, Fernanda Ibarra González, her daughter, was 15 years old and an analysis reported 10.43 micrograms of arsenic per liter in her urine. Almost twice what is considered internationally as a level of risk of arsenic in the body.

Researchers had analyzed the urine of 275 people in that region. “Doña Leonarda had 301 micrograms per liter,” Claudia González said in an interview about a neighbor; “Efrén, his son, 165”, he read from an inconceivable list that the academics gave him and of which he still has photographs. They had been drinking arsenic water.

Mother and son exceeded 47 times, she, and 26, he, the limit recognized by international scientific committees as the risk of tolerable intake for health. “It was clear to us why many relatives had died of cancer and why others are sick with cancer,” said Juan Ángel Trasviña, a specialist in environmental pollution. The population has never received any warning from local authorities about the levels of arsenic in the water supply, González says.

Trasviña and González have gathered evidence that points to the residues of 100 abandoned mines in the area as a source of arsenic, but this mineral, which is also found naturally in the earth’s crust, also reaches the water due to uncontrolled extraction, according to investigations scientists in Mexico and the world. Arsenic and fluoride have already reached wells in most of the country, in amounts higher than the maximum allowable level of the World Health Organization.

Claudia González, defender of water in Los Planes, Baja California Sur. Photo: Leonardo Castorena

An analysis carried out by Data Crítica and Fifth Element Lab of an official database that has spent years almost unnoticed revealed that arsenic, from being at high levels in 17 states during 2012, expanded to wells in 24 states in 2018, the last year of complete records. Although fewer water samples were taken in 2019 and 2020 than in previous years, arsenic levels continued to show elevated levels. And the authorities have not informed the population.

According to data from the National Water Commission (Conagua), there have been high concentrations of arsenic in wells in Guadalajara, Jalisco, in La Paz, Baja California Sur, in Hermosillo, Sonora; also in Villa de Cos, Zacatecas and in Tlajomulco, Jalisco, which are the new faces of a crisis that was previously limited to certain places in La Laguna, Hidalgo, San Luis Potosí and Guanajuato. Data from the government of Mexico City reveal that it is also present in wells of 6 of the 16 city halls of the capital.

Reina Castro, a researcher at the University of Sonora, affirms that cancer cases in Sonora are due to the consumption of arsenic. Photo: Rosa Luxemburg Stiftung

In 2018, the year in which the most samples were taken, 41 percent of the wells sampled exceeded the international threshold of risk of health impact for arsenic (0.01 mg / L). And these places or their water sources are not close to mines and abandoned waste as is the case in Los Planes.

The Plans are obvious in this analysis. This town, dedicated to agriculture, construction, and sport fishing, is one of the towns with the most toxic levels of arsenic in the groundwater of La Paz. This municipality occupies one of the first places in a lethal ranking: the number of wells with high levels of this mineral more than doubled between 2012 and 2019, according to the data analysis carried out for this research.

Aerial view of Los Planes, Baja California Sur.
Video: Leonardo Castorena

The network that measures expansion

To obtain indicators of water quality in Mexico, Conagua created the National Water Quality Measurement Network (Renameca), from which in 2012 it took samples at 3,858 sites, of which 3,039 were surface waters ( rivers, lakes, dams, coastal waters) and 819 groundwater sites (wells).

The database of this Network collects the results of the presence of various contaminants in 121 thousand samples taken between 2012 and 2020. The analysis of Critical Data and Fifth Element Lab focused only on the more than 11 thousand samples taken in wells that extract underground water; about 90 percent of the fresh, unfrozen water in the world is underground.

The analysis revealed that, in addition to arsenic, another mineral whose presence expanded remarkably in high concentrations this decade was fluoride, which, like arsenic, is also found in nature and has harmful effects on health. Consuming too much fluoride can cause bones to deform or make them brittle and brittle; It can also cause calcification of tendons and ligaments, according to the World Health Organization (WHO). This organism indicates a guide of 1.5 mg / L, but warns that to define national limits, factors such as climate and the volume of water intake, among others, must be considered. In 2012, fluoride was above the limit considered the risk of dental fluorosis by Mexican scientists and international agencies (.7 mg / L) in 25 states; in 2018 it was 30. That year, 41.

These elements reach the population’s drinking water because in Mexico only 257 water treatment plants are capable of removing arsenic or fluoride, and only 173 are in operation, according to a request for information made for this investigation to Conagua. There are 1,256 water treatment plants in the country, that is, only 1 in 10 water treatment plants remove arsenic or fluoride.

From tap water, arsenic passes into food that is cooked with it. The doctor Javier Morán discovered it in studies in beans, salsa, and literally even in soup. His colleague, Dr. Javier García Salcedo, explains that this mineral acts as a flame that “ignites the fuel” of any genetic predisposition to develop cancer, explained Javier García Salcedo. The internist doctor has seen the evolution of this problem in Torreón and Durango.

According to the baseline analysis, there are wells with fluoride concentrations that have exceeded 64 times the risk limit. It went from being present in  25 to 30 states from 2012 to 2018.


The Mexican standard for arsenic tolerates a risk more than double the international risk. “In the world, the norm is 0.01 milligrams per liter. In Mexico, 0.025. At the end of the day, you can have only 0.01, it should be 0, because metals accumulate. It is going to hurt you, it may take longer, but it is going to hurt you anyway ”, warns García Salcedo.

According to experts, in some cases, one of the first signs of exposure to arsenic in the development of large moles on the skin. Over time, the effects worsen. “Their feet turn black until they are cut off,” explained Dr. Javier García Salcedo. The doctor has treated around 300 cases of gangrene known as “black foot” in San Pedro and Francisco I. Madero since his years of study in 1973.

“In the case of arsenic, the diseases appear at 10, 15, 20 years,” explained Teresa Alarcón Herrera, an academic at the Center for Research in Advanced Materials (Cimav), of the National Council of Science and Technology. Prolonged exposure to this heavy metal is associated with the development of different types of cancer, cognitive deficiencies in children, infertility, and diabetes.

Inhabitants of La Laguna already show tissue death due to prolonged consumption of arsenic. | Photo: Jesús Peña / Vanguardia

The arsenic water that is drunk in Mexico exceeds 70 times the permissible limit by the WHO. It went from being present in  17 to 24 states from 2012 to 2018.

Millions of people exposed

In Mexico, more than 12 million are exposed to these toxic elements, but unlike Claudia González, they do not know it. Researchers such as Dr. Teresa Alarcón Herrera and other specialists from Mexican and American universities made a calculation: 8.81 million exposed to arsenic above the permissible limit according to the WHO and 3.05 million to fluoride, according to one of the most recent investigations.

Other calculations, such as those of the hydrogeologist José Joel Carrillo, estimate the exposure to fluoride —only in the eastern part of the Sierra Madre Occidental— at about 15 percent of the population, 19 million people. A study by the Ministry of the Environment and Natural Resources, obtained via transparency for this research, recognizes the exposure figure of 14 million exposed to both toxins, citing a study from the autonomous universities of San Luis Potosí and Guanajuato.

Exposure to arsenic could cause at least 13 thousand 70 additional cases of cancer concentrated in the northern and central states of the country, the most affected, according to Teresa Alarcón, a researcher at Cimav. These states have higher concentrations of arsenic and fluoride due to being on a volcanic axis.

However, this is not a complete photograph. These estimates are based only on the wells sampled by Conagua and not from all the wells operating in the country: “it is an underestimation of the real burden of exposure and disease for the country as a whole,” added Teresa Alarcón. Therefore, the projection of patients with cancer or other diseases due to the consumption of poisoned water could be higher.

But there is little that we can know. The information on the increasing levels of arsenic and fluoride in the water has not triggered the creation of an epidemiological surveillance program for the diseases they cause, according to the response via Transparency of the National Center for Preventive Programs and Disease Control of the Secretariat of health. The government only monitors dental fluorosis, the least harmful consequence of fluoride consumption. There is no monitoring program for diseases caused by ingestion of arsenic.

Furthermore, as of 2018, the federal government has taken fewer water quality samples each year from the monitoring network, which is the thermometer that allowed us to monitor the evolution of the problem. It went from 2,260 wells sampled in 2018 to just over half (1,192) in 2020.

Here nobody is saved

The wells of the monitoring network are located in the towns to monitor the quality of the water in the area. The presence of arsenic and fluoride has also expanded to regions such as the Guadalajara metropolitan area, one of the most populated in Mexico. The San Juan de Ocotán 1 well, which supplies the domestic network with water without first going through a water treatment plant, exceeded in 2016 and 2017 between 1.5 and 2.5 times the maximum permissible level set by the WHO for arsenic and up to 5 times the level for fluoride.

The consumption of fluoride produces fluorosis, which is manifested in stains on the teeth, a phenomenon that was seen in marginalized populations of the cities, where families drink water directly from the tap because they cannot afford bottled water, and that can now be observed in neighbors from wealthy Guadalajara colonies such as Colinas de San Javier, according to Kachadourian. 

The municipalities of Los Altos de Jalisco have arsenic levels above the WHO limit, except for Cañadas de Obregón, Cuquío and Yahualica. Mexticacán, Teocaltiche, and San Juan de Los Lagos top the list with the highest levels, according to research published in the Pan American Journal of Public Health. “In that area, there are deformities due to the high concentrations of arsenic and fluoride,” said Dr. Teresa Alarcón Herrera.

In Durango, independent studies have already taken samples from bottlers and concluded that the population ingests arsenic, even if they do not drink tap water. An analysis of the National Polytechnic Institute in 30 water purifiers found that in all of them the national and international norm in beverages for fluoride was exceeded and in 6 out of 10 that of arsenic, despite the fact that most of them showed a reduction between 20 and 97 percent the levels relative to the source wells for fluoride and between 14 and 97 percent in the case of arsenic. 

A database of the Mexico City Water System (Sacmex), obtained for this investigation, indicates that in 2020 the international arsenic standard was violated in 28 wells distributed in Tláhuac, Tlalpan, Coyoacán, Iztapalapa, Iztacalco, and Azcapotzalco. 

In Mexico City, the Chinamper territories of Xochimilco and Tláhuac have the highest levels of arsenic in surface waters in Mexico City recorded by the monitoring network. Although with comparatively lower levels than those seen in the rest of the country, its waters irrigate vegetables from the chinampas that go to the Central de Abastos.

Crop fields in Xochimilco, Mexico City. Photo: Gibrán Mena Aguilar

Research shows that, despite the fact that arsenic remains mainly in the root and stem of crops such as lettuce, or those of the jalapeño, serrano, and chilaca pepper, a small part can reach the leaves. 

According to the International Hydrogeology Association, with data also from Sacmex, between 2012 and 2017 the arsenic level increased in at least 57 wells in Mexico City in the central area of ​​Xochimilco, and northeast of Milpa Alta.

Arsenic is even sold in stores. According to reports obtained via a request for information from the Federal Commission for Protection against Sanitary Risks (Cofepris), samples were taken from 600 ml bottles. of Peñafiel mineral water, obtained from grocery stores in Jalisco and the State of Mexico, exceeded the Mexican standard, 0.010 mg / L for arsenic. In the most recent tests in late April and May 2019, three different bottles showed 0.0132, 0.0135, and 0.0172, respectively. In the United States, the brand’s mineral water was removed from consumer shelves in 2019.

 Report of the results of samples taken from 600 ml bottles. of mineral water Peñafiel in Jalisco.

Possible solutions

According to experts interviewed, up to this day, the government’s only effort to reduce exposure to arsenic has been to install water treatment plants that remove this mineral. But even those efforts are insignificant given the magnitude of the problem. To begin with, only 7% of the municipalities have a plant that treats the water they supply to homes. And only 1 in 10 existing water treatment plants removes arsenic.

There are two treatment plants in Hermosillo, neither of which removes this mineral. Near Los Planes, a water treatment plant was inaugurated in 2015 that would remove arsenic. The city council reported to the National Census of Municipal Governments that in 2018 it did not treat a single drop of water due to “equipment failures since its start-up.” The following year it didn’t work out either. “It works seasonally, for example, two weeks ago it worked, but not this one,” Claudia González said recently, in November 2021.

In Torreón, the president of Mexico, Andrés Manuel López Obrador, announced in March 2021 the construction of a new water treatment plant for the La Laguna region. “The president is thinking about the water treatment plant because it is urgent that the population have clean water free of arsenic, but what it represents is to free the groundwater from the aquifers so that the dairymen can use it up. The desert does not have the vocation of a dairy basin, “said Pilar López. 

Over the years, Dr. García Salcedo has seen part of that desert populate with cases of “black foot”. “The question is why do I have to remove the arsenic from the water if I can have water without arsenic avoiding overexploitation?”

The solutions proposed by the experts require major surgery. They imply rethinking the entire water concession regime that currently exists in the country. The solution proposals are waiting in the different versions of the General Water Law, which has been delayed for eight years in the Chamber of Deputies: putting meters that report the extraction of water from industries; charge for its exploitation in accordance with the profits of the concessionaires; reduce the concession to less than 30 years and prevent it from being automatically renewed; ensuring that only the water authorized in the concession is extracted and regulating and monitoring the construction and operation of wells are some of the points that the experts propose to regulate the water market in Mexico. 

Facilities of the Municipal Water and Sanitation System of Francisco I. Madero, in Coahuila, where drinking water must be made drinkable. Photo: Jesús Peña / Vanguardia

What most worries Fernanda Ibarra is the future of her daughters. When her mother told her in 2012 that she urinated arsenic, she thought of her offspring. “She explained it to me as it is, that she had arsenic, and what could happen, that it causes cancer and other diseases. What worried me the most at that time: ‘it was going to touch my children”. 

That fear that crossed her mind when she was a teenager took shape. Her young daughters are exposed to the same danger as she and her mother, just because they inhabit Los Planes. “My girl is already older and she drinks from that same water, from the one that comes down from the wells. We try to drink from what they bring from the city, but sometimes it runs out,” lamented Fernanda. 

Only 1 in 10 water treatment plants in Mexico removes arsenic or fluoride. 

Claudia González in Baja California Sur and Pilar López in La Laguna face the problem as a community, while governments of the three levels turn their backs on them. The delegation of Los Planes, the municipality of La Paz, has not informed the population about the danger “nor to deny that we are taking arsenic,” said Claudia González. Neither does the state government. But the federal government also leaves them to their own devices. 

In a press conference of the president, the then head of Conagua, Blanca Cisneros, said on September 11, 2020, that they protect the population by changing contaminated water sources for others that are not. “La Conagua has about five thousand, four thousand water quality intakes, which we have long before people drink the water. As soon as we realize this problem, Semarnat, Profepa, and Conagua go together and immediately change the supply source, ”said the official, appointed ambassador to France in April 2021. 

In response to a request for information, Conagua reported that they replaced seven water supply sources in 2014, but it was due to the Grupo México spill of copper sulfate in Sonora. They did it twice more in 2016 in Guanajuato, due to the presence of iron and manganese in wells. According to Conagua’s response, they have not made a single water source change in response to the presence of arsenic or fluoride. 

Near Los Planes, a water treatment plant was inaugurated in 2015 that would remove arsenic. The city council reported to the National Census of Municipal Governments that in 2018 it did not make a single drop of water drinkable due to “equipment failures since its start-up.” The following year it didn’t work out either.  

Near Los Planes, a water treatment plant was inaugurated in 2015 that would remove arsenic. Photo: BCSNoticias

The legacy 

Claudia González has spent very busy days, between the mobilizations, her work of informing the communities, and caring for the family. “Not in my crazy dreams did I think that they would call me an activist, which is what people ask me if I am. It was something that, due to these circumstances, was forming me and here we are, in the fight. My intention is to instill in my daughters and my grandchildren that we must defend the land and water, against everything, ”says Claudia González.

“My intention is to instill in my daughters and my grandchildren that we must defend the land and water, against everything,” says Claudia González. Photo: Leonardo Castorena

And their fight has already taken effect. Her daughter Fernanda Ibarra says she is very proud of the defense of the territory that her mother undertook years ago. Then Claudia and her organization organized lotteries among the townspeople, inviting a doctor here and there from time to time to inform them of the dangers of arsenic in water. Fernanda learned from her mother. Now she does everything possible to ensure that her daughters do not go through what she went through. The lesson is that a decent life must be taken care of before the gains of private interests, he says. It is a lesson that he wants to leave for his daughters. 

How to find out if the water that comes into my house has arsenic or fluoride? How do I know if I have arsenic in my body? What other alternatives are there to combat water pollution? Find the answers in the full report that you can consult here.

The journalistic investigation carried out by identified the levels of

The journalistic investigation carried out by Data Crítica Quinto Element Lab includes posters that help you to know and disseminate the number of wells with arsenic and fluoride at risk levels in the municipalities monitored by the national network of Conagua. Locate your entity, and if your municipality has wells registered with these high levels, you can download the poster and print it to inform your community. Enter this link.


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