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

Mexico's dry Laguna region is facing an arsenic problem in drinking water as a result of overexploitation of aquifers and lack of rainfall.

BUENOS 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.

CANCER PROBLEM

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.

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