Arsenic contamination of groundwater, focussing mostly on Argentina and Chile

During the 130 million years that the South American continent was moving away from Africa, pushed by the continual movement of tectonic plate action, a number of extreme events occurred to the Earth’s crust. The landmass was ever changing, and today, is divided into countries; the indigenous early human population is now dominated by recent history of European human conquest. But human existence is but a blinking of an eye compared to the millions of years this landmass and life thereon, was evolving.

One striking feature is the huge Atacama Desert of western South America

Image of Atacama Desert and map of its location

This desert formed around 10 million years ago, whilst the landmass of South America was isolated. (It was 4 million years ago that South America became joined, over a millennia, to North America).

In May (2019) a team of scientists, from France’s Aix-Marseille Université, made the extraordinary discovery – comprising of 388 separate meteorites – in South America’s Atacama Desert. Some of these ancient meteorite collection date back two million years – the oldest-ever found on Earth.

Contrast these wonders of our planet to the early human experience of being the first explorers to find the Atacama Desert.

The Earth changes and evolves and is host to our presence, but we can only interact with it with survival in mind. Once satiated, feeling safe, we might use our brains to try and contemplate the making of this diverse and incredible universe.  

There is recent evidence (see that a comet set the Earth on fire, and one of the impact craters has been found at the southern tip of Chile. This was around 12,800 years ago, (Pleistocene) and is evidence the event created a severe climate shift. In this location the impact would have caused widespread destruction, characterized by biomass burning, megafaunal extinctions and global cooling.

The landscape of the lush vegetation was transformed by what is termed the Younger Dryas, causing advances of glaciers and drier conditions, over much of the temperate northern hemisphere. This event is believed to have caused widespread destruction and the demise of the Clovis culture in North America.

Image of climate change graph

Whilst this catastrophic interruption to life evolving in South America occurred, there were constant eruptions along the Volcanic Belt of the Andes, which continue today. 

Geological processes are a constant presence as the crust of the Earth continues to move and reshape itself. Yet humans and all life adapt and evolve as water, food and shelter are sought.

Number one priority! All living things must have free, clean, pure and fresh drinking water in order to survive. Those without it, and there are millions, suffer until those who have succeed in helping those who have not. (Example

Caleta Vitor, Chile


As tribes of hunter gatherers, of probably between twelve to twenty in number, slowly arrived on the Pacific Coast of South America, they ate molluscs and fish from the sea, but sought fresh water by moving inland, or collecting rainwater, perhaps in empty large shells. It has been postulated that the fish diet probably was crucial to brain development and helped them solve problems of survival more effectively.

But those who arrived at what is now known as Caleta Vitor, on the Pacific coast of northern Chile, drank from what appeared to be clean, pure water. They were not to know it carried a dangerous toxin which continues to form in groundwater today. Arsenic.

There is evidence that people of numerous pre-Columbian civilizations in northern Chile suffered from chronic arsenic poisoning between 500 and 1450 AD, through consumption of contaminated water. 

Now a new study has found evidence of arsenic poisoning across all major cultural periods in the region, spanning several millennia. The researchers, James Swift of the Australian National University and colleagues from several other institutions in Australia and Chile, performed plasma mass spectrometry trace element analysis of human bone and tooth samples. The samples came from 21 burials covering the period from 3867 to 474 BP (before present) excavated at the site of Caleta Vitor on the Pacific coast of northern Chile.(see

These would be hunter gatherers, not communities forming civilisations. They buried their dead, no doubt valuing the person who had suffered in their midst for some time before their death. This habit has led to these remains being uncovered by the researchers. Coastal and inland Chilean Diaguitas (see later about the Diaguitas tribes) traded in this area as evidenced by the archaeological findings of mollusc shells in the upper course of Andean valleys. These were most likely the ancient people who were the wandering, indigenous tribes, seeking sustenance along the Pacific coast in what we now think of as Chile. They would find the cold Atacama Desert, a barren wilderness, unsuitable for a human centre for settlement. Even the Incas penetrated into the northern portion of what is now Chile but were never able to develop the area for the same reasons of barrenness.

These early explorers sought fresh drinking water inland, as a priority. In the case of those who died of arsenic poising, what they found looked safe to drink and no one died within a short time of drinking it. They had no idea it was poisonous, contaminated with arsenic. Those people grew ill very slowly, so they could not work out what was killing them in such a painful and cruel way. Animals with shorter lifespans would not be affected, therefore no carcasses of animals lay by water contaminated with arsenic.

The Diaguitas and Catamarca 

Images of Catamar

Vista_aérea_de_San_Fernando_del_Valle_de_Catamarca,_Argentina.jpgjlazarte Catedral_Basílica_Nuestra_Señora_del_Valle,_Catamarca.jpg: Agus ferrocarril Archivo_y_MH_Catamarca.jpg: Claudio Elias El_Jumeal.jpg: Stefan sauzuk Templo_de_San_Francisco,_Catamarca.jpg: 

There were no borders when humans first roamed South America, so early humans explored this landmass, forming numerous and often warring tribes, but coming together only to face the threat of early civilisations such as the Incas or the Spanish Conquistadors.

Before the arrival of the Spanish conquest, most of today’s Catamarca was inhabited by the Diaguitas indigenous people, including the fierce Calchaquí tribe.

The indigenous tribal peoples have lived in the lush river canyons of this region for over 12,000 years. These were the Pulares who lived in the Chicoana region, the Jamalaos in Sumalao, the Luracataos and Colomes in the Tacuil region, the Hualfin in Angastaco and Tucumanahao. 

To the south of San Carlos were the Quire-Quire, the Animana, the Chuschagasta, the Cafayate, the Tolombon and the Colalao. In the Yocavil Valley lived the Amaicha, Quilmes, Yocaviles and the Caspinchango. To the south were the settlements of the Abaucanes in Andalgala and Hualfin. Other tribes are the Tinogasta, Palcipas, Pom’an, Capayan and Fiambala all of which contributed to the enrichment of the ethnic spectrum in this region. 

The ‘Diaguita’, combined by the Spanish invaders under this umbrella name, included many tribes that had united years earlier to defend themselves against the intrusion of the Incas from the North. Despite hundreds of years of invasion and colonization by first the Inca and then the Spanish, the descendants of these original people still live in their ancestral homeland……….Of special importance to the Calchaquí was their hairstyle. They wore it long, and it was considered despicable to cut a person’s hair. According to the writings of Quiroga in 1903, one of the most insulting punishments inflicted by the Spaniards was to shave off the Indians´ hair. Pincers made of copper lead us to believe that the Diaguita plucked their hair with an eye to fashion. They decorated their straight, black hair with headbands, feathers, plaits, and hair needles made from cactus wood, horn, and silver. In early times even an occasional deformed skull was incorporated into a hairstyle.

Valuable jewelry was made in various zoomorphic shapes from precious metals. Silver and gold plates were fashioned into pectorals, bracelets, discs for the forehead and sewn into clothing. Pins to close tupus had filigree decorations. Necklaces and earrings were made of both precious and semi precious stones.”


Arsenic found in drinking water worldwide

Today, arsenic found in drinking water is a worldwide problem, and not least in the Americas.
The lands once inhabited by indigenous tribes are now populated by people who have formed rural farming communities; people who have built cities and industrialised the landscape; people who are very poor and struggle with day to day poverty; and a smaller percentage who live a comfortable life. Every single person requires water free from toxins, but this is not straightforward for those who have no choice but to live in contaminated regions.

There is now a growing body of knowledge of how arsenic gets into groundwater and solutions are being tested to provide populations with arsenic free drinking water. Each location requires varying solutions, with no formulaic answer which might solve the worldwide cases”

The World Health Organization (WHO) ranks arsenic as one of 10 most concerning chemicals from a public health standpoint. Prolonged exposure to arsenic, particularly in drinking water and food crops that require irrigation, increases the risk of cardiovascular, dermatological, and neurological diseases, as well as various forms of cancer. At least 4 million residents of Argentina, Chile, Mexico, El Salvador, Nicaragua, Peru and Bolivia are exposed to dangerous concentrations of it. Bangladesh is the worst affected country in the world by arsenic contamination. More than 60% of the groundwater available in Bangladesh is highly contaminated with arsenic. About 50-77 million of the total population of about 164 million is under extreme threat. 

Arsenic contamination of groundwater is a form of groundwater pollution which is often due to naturally occurring high concentrations of arsenic in deeper levels of groundwater. In Bangladesh, it is a high-profile problem due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people. Additionally, mining in India can produce waste which gets washed into Bangladesh in the monsoon season, and that waste contains a range of toxins.

A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water. The problem became a serious health concern after mass poisoning of water in Bangladesh. Arsenic contamination of ground water is found in many countries throughout the world, including the US.
Image of Bangladeshi, poisoned by local water arsenic contamination. These communities cannot find locally safe drinking water.

Approximately 20 major incidents of groundwater floarsenic contamination have been reported. Of these, four major incidents occurred in Asia, in Thailand, Taiwan, and Mainland China. Locations of potentially hazardous wells have been mapped in China.

Individuals with chronic exposure to arsenic are at higher risk of death at younger age because arsenic is such a toxic agent that affects all systems of human body,” says Dr Muhammad Yunus, emeritus scientist and senior author of a study published in Environment International based on a 13-year long observation on indications of higher mortality risk rate of young adults.

Young adults who passed away due to cancers, cerebro-vascular, cardio-vascular and respiratory diseases – were found to have a higher exposure to arsenic-laced water. See

Regardless of localized inputs of arsenic from human activities, much of the contamination of groundwater by arsenic was shown to arise from geogenic sources which affected groundwater in many countries. Arsenic is a natural component of the earth’s crust and is widely distributed throughout the environment. On land, rocks which are exposed to certain geological and geothermal activities can contribute to major sources of arsenic deposits if they are rich in minerals containing arsenic like Realgar (As4S4), Arsenopyrite (FeAsS), Anargite (Cu3AsS4) and Orpiment. The major cause of contamination of arsenic in groundwater is the mobilization of natural arsenic on sediments. If the minerals are subjected to the right chemical conditions under the ground, the arsenic content in them can dissolve in the surrounding groundwater accumulation. The main anthropogenic sources for contamination of groundwater with arsenic are mining, burning of fossil fuels, use of arsenical fungicides, herbicides and insecticides in agriculture and wood preservatives. The degree of groundwater arsenic contamination by anthropogenic sources is much less compared to the natural sources; however, their contribution cannot be neglected. In the United States, the arsenic contents have been reported to be sourcing from geogenic sources like up-flow of geothermal water, dissolution of or desorption from iron oxide, and dissolution of sulphide minerals; and also, from anthropogenic sources such as copper smelting. 

The source of arsenic in India is geogenic as well as anthropogenic. Arsenic is present in the alluvial sediments of the Delta; and the chemical industries along with mining contribute to the anthropogenic causes of arsenic in groundwater. The presence of arsenic in groundwater exceeding the standard limits set by the government and its toxicology pose serious health concerns. The severity of the problem is alarmingly high. Its long-term exposures are fatal. Arsenic poisoning immediately causes vomiting, abdominal pain, and diarrhoea which might be followed by muscle cramping, numbness and at times death. 

The long-term exposures can be indicated by pigmentations on skin, hyperkeratosis and skin lesions which might prove to be early signs of skin cancer. Along with skin cancer, there may be developmental effects, diabetes, pulmonary and cardiovascular disease.”

Image of Worldwide Map locations of arsenic poisoned water, from above report

Argentina, South America

Natural geological factors are to blame for most arsenic contamination in Mexico, Argentina, Chile, Peru, and Nicaragua, but human activities also lead to huge arsenic contamination problems. Mining and smelting are responsible for much of the problem in Chile, Bolivia, and Peru. In Brazil, contributing to the problem are electrolytic processes in metal production. A smaller but significant source is arsenic pesticide, used mainly in Mexico. Generally, though, most arsenic in Latin American surface water and groundwater comes from minerals produced by Andes Mountains Tertiary and Quaternary volcanism.

Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings;  including rift systems and extensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains apart from a large range on crustal thicknesses and magma ascent paths, and different amounts of crustal assimilations. (

Image of Andean Volcanic Belt

Volcanic activity can release large amounts of arsenic to the environment.

Every year, natural sources contribute about 1/3 of the total annual release of arsenic to the atmosphere. Most of this comes from volcanoes.

Groundwater in contact with rocks that are high in arsenic MAY contain high concentrations of arsenic – this is a natural source of arsenic. Many of the world’s most troublesome problem spots are due to naturally high in arsenic in groundwater.

Argentina, particularly the northern and central areas, such as the province of La Pampa, have high concentrations of arsenic. In large parts of rural Argentina people depend on groundwater whose As content exceeds the Argentine drinking water standards (0.05 mg l−1). 

In La Pampa, arsenic levels vary widely by locality. Studies have observed levels of <4 µg/L to 5,300 µg/L in the region. Some urban areas use reverse osmosis treatment, but it’s impractical in rural areas and cattle lands. A 2012 study of arsenic contamination effects in the Rioja plain, Pampa hills, and Chaco-Pampa plain found an increased risk of colon cancer in women, and lung and bladder cancers in both sexes.

Anthropocene Impact through mining processes

Examples of intensive mining in Latin America show:

In Bolivia, bordering with Argentina and Chile
It’s destroying lives

In Bolivia, the average miner in the tin mines of Potosí will live only 35 to 40 years – a life more than 25 years shorter than the average Bolivian person. At least 300,000 children as young as 5 work in Columbian mines.

The children suffer

Almost all children in the Peruvian town of La Oroya have dangerously high levels of lead, arsenic and other toxins in their blood. More than 40% of the children under 5 have mental deficiencies. The cause is the town’s heavy pollution from lead, zinc and copper mining. The owners were prosecuted and fined. This complex is to be under new ownership

Images Oroya complex 

The mining of raw materials for electronic products—including silicon, aluminum, copper, lead, and gold—contributes to increased respiratory problems for workers, such as silicosis, tuberculosis, bronchitis, and lung cancer. Gold mines are the leading source of mercury air pollution in the U.S.

Anxiety about the destruction caused by mining in mountainous landscapes is illustrated in this blog:;
Images from above blog

Agus ferrocarril derivative work: Bleff • CC BY-SA 3.0

Located in an arid and semi-arid climate zone, the scarce water resources determine the human settlement pattern. Agricultural activities are concentrated in the pockets and valleys between the mountains. In the east the population is concentrated around a number of water courses, water being distributed by canals and irrigation ditches.

The constant threat from mining activities looms over these oases in the desert.

Seven years ago this was the huge list of mining operations in Argentina


In Chile, high levels of volcanic arsenic are affecting rural water supplies and agriculture through contaminated soils and irrigation water. As Ioanna Kakoulli, an archaeological scientist at the University of California, Los Angeles, explained that in Chile, sediments are also rich in arsenic because of copper-mining activities in the highlands. It is too easy to explain arsenic levels through natural causes.

Compounding the misery caused by already high levels of natural toxic levels of arsenic, copper mining is an additional source of arsenic contamination.(

Antofagasta has a reputation of being anti-union, anti-worker and anti-environment and has exhibited such behaviors wherever they have decided to exploit low-grade copper sulfide ore anywhere in the world. (See

……..The International Copper Study Group’s (ICSG), most recent projections see world mine production increasing 4.2% to 19.5Mt in 2016 with the market moving into a deficit of around 130,000t as demand growth outpaces production growth, after a surplus of 41,000t in 2015……….Latin America still leads the world in copper mine production. Latin America’s share of global mined copper output as a region grew from 19% in 1960 to over 40% in 2014, and this share will continue to expand as the project portfolio evolves. (

There used to be villages in the Atacama Desert, but now they are preserved as museum pieces for tourists who have come to see the biggest copper mining open pit in the world. (

Chuquicamata (/tʃuːkiːkəˈmɑːtə/ choo-kee-kə-MAH-tə), or “Chuqui” as it is more familiarly known, is by excavated volume the largest open pit copper mine in the world, located in the north of Chile, just outside Calama at 2,850 m (9,350 ft) above sea level, 215 km (134 mi) northeast of Antofagasta and 1,240 km (770 mi) north of the capital, Santiago.

Hector Pumarino Soto suggests that “Calama” stems from the Kunza word “Ckara-ama,” which means “town in the middle of the water”. Until the middle of the 20th century, the urban site of Calama and the surrounding oasis were flanked by the River Loa on two sides, and the fertile plain and swamps on the other sides, giving the location the appearance of an island in the middle of the desert surrounded completely by water. Its banks have been inhabited from early times. Evidence of this is the notable number of geoglyphs, petroglyphs and pictographs that are found along its course and in its upper basin.

Northern Chile’s rivers are the main causes of arsenic contamination (Mukherjee et al 2006). The region is drained by the Rio Loa river which has an arsenic concentration of 1400 μg L−1 and its tributaries have about 1000 μg L−1 (Mukherjee et al 2009).

Chuqui -as workers call Codelco’s flagship mine- together with the nearby Radomiro Tomic mine produced 653,000 tonnes of the company’s total 1.8 million tonnes of output last year.(see

At present, the state-owned miner is seeking to transform the 100-year-old open-pit deposit at Chuquicamata into an underground mine by 2020, when mining at the open-pit ends.

In 2013 David Lowell, a legendary octogenarian explorer credited with finding the Escondida copper deposit, among others, hoped he could find the answer to one of the world’s greatest exploration mysteries: finding lost – or believed to be lost – Chuquicamata copper ore.

The Chuqui mystery is this: a fault, called the West Fault, cuts through the Chuqui ore body and appears to have moved a chunk – how much is not clear – of Chuqui ore elsewhere, where or exactly how far is uncertain. But most guesses, those made in a so far fruitless search for lost Chuqui ore, have put it somewhere about 15 to 20 kilometres to the south on a property that is known as the Ricardo project.

It’s a roughly 16,000 hectare property on the edge of the Chilean town of Calama. The pursuit for this wealth creating and arsenic inflicting ore never seems to end. Will Calama become another ghost town?

Image of Geothermal Vents, Calama

In geothermal reservoirs that are deep seated, leaching helps the release of arsenic which are brought to sub-surface level by the uprising activity of the geothermal fluids. At high temperatures, arsenic occurs in Arsenopyrite (FeAsS) or simply arsenic bearing pyrite. ​Bundschuh​ These minerals dissolved in geothermal fluids, after reaching the subsurface zone, get adsorbed to the sediments when in excess. Later on these sediments work as source for arsenic when the concentration of iron decreases in the surrounding waters. (Cornett et al 1992, Bright et al. 1994) When these sediments weather, they release bivalent Fe in an oxidising environment, which sorbs the co-weathered arsenic. The iron oxyhydroxide rocks adsorb arsenic released from these sediments. Redox processes in these rocks trigger the reductive dissolution of iron oxides into the surrounding aqueous phases along with a substantial amount of arsenic through different biogeochemical processes ​(​Singh 2006​). 

Microbes also promote arsenic concentration in fluids by oxidation or reduction to produce As (V) and As(III) respectively. Low pH promotes the concentration of the aqueous species H2AsO4- under oxidising conditions and high pH will promote HAsO42- under the same conditions. Under reducing conditions, arsenite dominates in the form H3AsO30 (Kinniburgh et al 2003).”

An architect group say

Calama PLUS is a public-private initiative aimed to compensate the Calama inhabitants, in response to their massive and constant complaints about the negative environmental impact of mining activity on the city. It is intended to improve, on one hand, its urban quality, and on the other, to preserve and expand its condition of oasis. With a participatory design process, the master plan includes 23 projects to improve the city ranging from urban parks, public spaces and schools to proposals on how to use more efficiently scarce water resources.

Our planet cannot take much more plundering. We must move back from expansion and become agnostic to growth of corporate outputs, worldwide. All corporate mining activity must utilise cutting edge technology that will not negatively impact the water, fishes, trees and land -as all of them are interrelated. Failing that, they should be prosecuted for the crime of ecocide which may soon become an internationally declared law.

About borderslynn

Retired, living in the Scottish Borders after living most of my life in cities in England. I can now indulge my interest in all aspects of living close to nature in a wild landscape. I live on what was once the Iapetus Ocean which took millions of years to travel from the Southern Hemisphere to here in the Northern Hemisphere. That set me thinking and questioning and seeking answers. In 1998 I co-wrote Millennium Countdown (US)/ A Business Guide to the Year 2000 (UK) see
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