“But I had no way of knowing if the symptoms were really due to mercury poisoning, because we don’t have equipment” for analysis, Manrique said.
No one has done a health assessment of Peru’s miners or townspeople to check for symptoms of mercury poisoning.
But a new study raises concerns. While most urine samples collected from about 200 people in Huepetuhe last year showed mercury levels below the World Health Organization limit for occupational exposure, a few were extremely high, according to Dr. Jonh Astete, who coordinated the study by Peru’s National Institute of Health.
Astete said some of the highest mercury levels were in people who were not directly involved in mining, but who lived near places where gold is bought and sold, such as the shop where the emissions were too high to be measured by the EPA’s gauge.
Every mining town has gold shops, all emitting mercury. About a dozen of these shops are clustered in less than two blocks across the street from Puerto Maldonado’s open-air market, the town’s main shopping area. In addition, officials say there are at least eight shops elsewhere in town, and some people probably process gold clandestinely in their homes.
Working under metal hoods with no filters, the shopkeepers heat the gold to vaporize the mercury before paying miners. During the burning, which takes several minutes, shop employees and customers are exposed to high doses of mercury vapor. Some shops have pipes leading outside, so the vapor spills into the air above the heads of shoppers passing by, near the windows of nearby low-budget hotels.
During a pilot study in 2009, Fernández found one shop in Huepetuhe where mercury averaged 450 micrograms per cubic meter of air—22 times higher than the World Health Organization’s occupational health standard — with spikes as high as 1,000.
Working with Argonne National Laboratory, the researchers devised a simple filter made of a barrel fitted with metal baffles and a fan, which local metalworkers can fashion for about $500. After a filter was installed in the shop, the levels dropped to about 40 micrograms per cubic meter, twice the international standard.
When the EPA team, headed by Marilyn Engle of the EPA’s Office of International Affairs, returned to Puerto Maldonado in February, they found that several other shops had installed similar, locally made filters. Their study will analyze the filters’ effectiveness.
As bystanders watched curiously, the EPA team set up metering equipment in black cases resembling portable speakers on the sidewalk outside shops. Donning respirators, they gave shop employees individual meters to wear for a work shift, then inserted tubes and traps into the hoods to measure elemental and gaseous mercury.
The team will use those data not only to calculate shop emissions, but also to model dispersion of airborne mercury.
Worldwide, informal mining like that in Madre de Dios releases between 650 and 1,000 tons of mercury a year into the air and waterways, according to the UN Environment Programme.
The threat is even more acute in La Rinconada, a one-time mining camp in the Andes that has grown into a town of about 40,000, with more than 200 gold shops. While miners in the Amazonian lowlands separate gold flecks from river sediment, those in La Rinconada drill ore from the mountains, then use huge grindstones to crush it with mercury.
They take the entire amalgamated mass – which Fernández said could weigh as much as a kilogram, half of which is mercury – to a shop for burning. Because of the mass, the process can take half an hour or more, exposing shop workers and customers to higher mercury levels for a longer time than in the shops in Puerto Maldonado.
In near-freezing temperatures, the vaporized mercury condenses quickly, precipitating into gutters and onto the street, and even pooling on the floor of shops or adjoining living quarters, Fernández said.