Adobe Homes in Peru's Andes Tell Centuries-Old Toxic Tale

High in the Peruvian mountains, the ancient city of Huancavelica once contained North America's largest mercury mine. The legacy of its tainted soil remains. Image: Flickr/Roberto Bustamante

HUANCAVELICA, Peru ? Sonia Salazar?s house, like most in her neighborhood, is built of adobe bricks made from mud that soaked up centuries of emissions from mercury smelters.

Now scientists are trying to determine whether those houses ? in the shadow of a hill that once held the hemisphere?s largest mercury mine ? pose a health hazard to their inhabitants.

In the 16th and 17th centuries, mercury furnaces blasted day and night around this town high in the Andes Mountains. Eventually the town expanded over smelter sites and waste piles.

The researchers already have found high levels of mercury contaminating the soil as well as adobe walls, dirt floors and the air inside some houses. They are now analyzing people?s hair to measure their mercury exposure.

Salazar, who is raising her four children in one of those houses, is among the residents waiting to hear whether they are being poisoned by their own houses.

?It?s worrisome,? Salazar said. ?It?s like an illness that gets into children.?

Huancavelicans call their town the tierra del mercurio ? the land of mercury ? and even the mayor recalls having played, as a boy, with little silver balls that oozed out of the sides of ditches or building foundations.

The capital of a region with some of Peru?s highest poverty, malnutrition, and infant mortality rates, Huancavelica grew up around a plaza still flanked by colonial buildings. Residential neighborhoods gradually spread along the river and up the hillsides.

?Eighty percent of the houses are made of adobe. Those are the people who have the fewest resources,? said Rub?n Espinoza, an archaeologist and anthropologist working with the mercury study team.

The study, which combines historical detective work with scientific analysis, might never have happened had it not been for the bizarre behavior of a priest.

Historian Nicholas Robins, director of the non-profit Environmental Health Council and a teaching assistant professor at North Carolina State University, was researching an 18th century Indian rebellion in Peru when he stumbled across a colorful description of Juan Antonio de los Santos. The priest?s erratic behavior and violent outbursts terrified parishioners and led a colonial government official to suggest that his superiors commit him to an insane asylum.

The priest had spent years in Potos?, Bolivia, at the foot of Cerro Rico, the ?rich hill? that for centuries supplied the silver that fueled global trade. Like small-scale miners today, colonial miners used mercury to extract silver from ore, sending tons of toxic vapor wafting over the city.

Robins wondered if the colonial cleric might have been suffering from mercury poisoning. The question led him to examine historical records of the amount of silver produced in Potos? and the mercury used to extract it.

Robins estimates that miners in the Bolivian town used some 39,000 metric tons of mercury to produce silver between 1574 and 1810. Much of that mercury came from Santa Barbara Hill, which looms over Huancavelica, about 12,000 feet above sea level. The main mine portal, now sealed, still sports a colonial arch and Spanish coat of arms.

The Spaniards? forced-labor system sent tens of thousands of Andean Indians into Santa Barbara?s labyrinth of tunnels to dig cinnabar ore. So many workers perished that Santa Barbara became known as ?the mine of death.?

When cinnabar ore is heated, the mercury that vaporizes can be condensed, captured and stored as a liquid. Based on colonial records, Robins calculates that miners in Huancavelica produced about 68,200 metric tons of mercury in the 16th and 17th centuries, and about one-fourth of that was released into the atmosphere from smelters.

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