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HomeTopicsClimate change & carbon tradingAs the climate dries, Mexico's milk region faces arsenic threat

As the climate dries, Mexico’s milk region faces arsenic threat



By Ana Belluscio*

laguna_regionMexico’s dry Laguna region is facing an arsenic problem in drinking water as a result of overexploitation of aquifers and lack of rainfall. Photo: Gonzalo Garcia VargasBUENOS AIRES, Argentina (AlertNet) – Mexico’s Laguna Region is famed as the country’s largest milk-producing area. But overexploitation of groundwater resources has combined with the effects of climate change to give the region a more dubious distinction. The remaining water supplies are contaminated with arsenic, and related rates of cancer are well above the national average.

Spanning parts of two states, Coahuila and Durango, in the north-central part of the country, the Laguna Region (known in Spanish as the Comarca Lagunera) is named after the numerous lagoons and ponds that were once found there.

But the construction of dams on the two main rivers, the Nazas and Aguanaval, in the 1950s led to the disappearance of the lagoons. The area is now largely semi-arid.

Dairy farming has taken a further toll on water resources with the planting of thirsty alfalfa crops to feed cows. A 2006 study found that milk production in Mexico required almost three-and-a-half times as much water per tonne as in the United States.

“The Laguna Region is the largest milk-producing region in Mexico, producing about 7 million litres of milk per day in a desert where rainfall does not exceed 200-250 mm per year,” explained Francisco Valdes Perezgasga, a researcher at La Laguna Technological Institute in the city of Torreon, in Coahuila.

“From 1992 to 1999 we suffered intense droughts and 2010 was the driest (year) in 100 years,” Valdes Perezgasga. Total rainfall for the region in 2011 was less than 100 mm, he said.

According to Valdes Perezgasga, the effects of climate change are exacerbating the overexploitation of existing aquifers.

Deep wells fitted with pumps were drilled from the 1950s onwards to extract water for crop irrigation. Experts say the construction of cement-lined irrigation channels began to slow rainfall from recharging the aquifer.

As rainfall also began to decrease and the main aquifer’s water levels fell, water from a second aquifer with high concentrations of heavy metals and arsenic began to pollute the region’s water supply.

As a result, the region’s more than 1.5 million residents now drink water contaminated with high levels of arsenic, an unexpected health impact of the region’s drying climate and its overexploitation of water resources.

Mexican law sets the safe limit for arsenic concentration at 0.025 mg/litre, two-and-a-half times higher than the level recommended by the World Health Organization. But in the Laguna Region contamination is as high as 0.08 mg/litre.


Health experts say the Laguna Region has rates of cancer two or three times the national average.

“We have confirmed an increase in the incidence of certain types of cancer, such as skin and gallbladder, and cases of genetic damage due to arsenic,” said Gonzalo Garcia Vargas, a professor of pharmacology and toxicology at Juarez University in Durango state.

Matilde Suarez, a health worker in Finisterre, Coahuila, said that in her community of 600 people have been suffering the effects of arsenic contamination for more than eight years.

“There are people here with amputated fingers, legs or arms,” a consequence of the poisoning, she said. Several have died.

Drinking water with significant levels of arsenic can cause a range of health problems, including skin cancer, diabetes, nervous system disorders, hearing loss and digestive problems.

Long-term exposure to arsenic may also lead to an increase in cancers of the lungs, kidneys, liver and other organs in 20 or 30 years within the population, Garcia Vargas said.


The state governments of Coahuila and Durango are taking different approaches to the problem. In Coahuila, high-volume filtration systems have been built near the most contaminated wells. These allow large volumes of water to be filtered before distribution, but they are not yet fully operational, according to Garcia Vargas.

The state of Durango has chosen to distribute home water filters. Miguel Calderon Arambula, director of the state water commission, said that there are plans to install 40,000 filters in the Laguna Region within Durango, where 800,000 people live. However, only 5,000 filters have been delivered so far.

One problem is that the filters will not be used to purify water used by dairy cows. According to Garcia Vargas, a small fraction of the arsenic contained in the water can pass into the milk supply. Although concentrations are too low to be harmful to adults, he said that it could be potentially dangerous for children feeding only on milk.

“Fortunately, children rarely drink cow’s milk but rather powdered milk, which usually undergoes a quality control process,” he said.

Calderon Arambula said there are no records of arsenic poisoning from drinking milk, and that farmers are responsible for ensuring that the water drunk by cattle meets the national health standards.

In the meantime, people are starting to become more aware of the consequences of arsenic exposure. Those who can afford it buy filtered water, said Ignacio Chong Lopez, president of the Citizens’ Council for Water, a non-governmental organisation.

But those that do not have the means to buy the purified water continue to be exposed to arsenic poisoning, said Chong Lopez. This is particularly true in rural populations, where the most contaminated wells are usually located.

Valdes Perezgasga believes that the limits of the region’s water supply should have been respected.

“But we wanted to live producing milk like we were living in Asturias (in Spain) or with green gardens like Britain,” he said.

* Ana Belluscio is an Argentine journalist who covers environmental and science issues. This story is part of a series supported by the Climate and Development Knowledge Network.

Taken from http://www.trust.org/alertnet/

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