Metal contamination ‘critical’ in Peruvian highlands

[BUENOS AIRES, SciDev.Net] One of the most iconic ecosystems of the Peruvian plateau, the Junín Lake basin, suffers from “critical” levels of arsenic, lead and cadmium contamination, leading to health risks including cancer, according to new analysis.

The study published in the journal Science of the Total Environment found that 99 per cent of the area has “very high to ultra-high” ecological risk and contamination levels. It revealed a “100 per cent carcinogenic risk” for adults, with children also highly exposed to arsenic, a highly toxic metalloid.

“The levels of arsenic are extremely high, as are those of lead and cadmium, far exceeding acceptable thresholds,” Samuel Pizarro, one of the authors, told SciDev.Net.

“The combined carcinogenic risk is unacceptable. The amount of chromium found is also significant and poses a serious threat to human health.”

The study was conducted by researchers from the National Institute of Agricultural Innovation of Peru and the National University Toribio Rodríguez de Mendoza.

They tested the spatial distribution, ecological risk and human health implications of 14 heavy metals, metalloids and trace elements in more than 200 samples taken from surface soils surrounding Lake Junín — also known as Chinchaycocha.

“This assessment reveals critical contamination by potentially toxic elements in the Junín Lake watershed, with arsenic, lead, cadmium, and zinc concentrations substantially exceeding ecological and human health thresholds,” the researchers wrote.

Levels of the toxins exceeded ecological thresholds by more than 100 times in agricultural areas, they added.

Part of the Junín National Reserve, the area is home to about 50,000 people, including urban and rural populations.

“But the impact reaches 1.3 million people because some of the water is then used in the valleys and in dams downstream,” said Pizarro.

He added that further work is needed to calculate the size of that impact, and the effect on children and pregnant women.

‘Sink for metals’

The Junín Lake area is one of the most emblematic ecosystems of the Peruvian highlands, says Dennis Ccopi, one of the study’s co-authors.

“At 4,100 meters above sea level, it is the second largest body of water in the country and the source of the Mantaro River, which feeds agricultural areas in the valley,” he said.

He said the ecosystem had become a “sink” for metals and metalloids, which accumulate in water, sediments, and grazing soils.

“This affects food and exposes local communities that use the land and water,” he added.

The contamination is linked to mines abandoned for a century or more, Ccopi explained, as well as agriculture and urbanisation. Nestled in the central Peruvian Andes, the highland area has a mining tradition dating back more than 300 years.

“There is a bioaccumulation process because the animals around the lake consume contaminated fodder,” Pizarro added.

Another co-author, Alberto Arias-Arredondo, is originally from the area and recalls that pollution was a problem when he was growing up. Now, he says, the study provides robust evidence of the scale of the issue.

Researchers systematically tested the area using grid sampling points around the lake and machine learning to analyse the data along with other environmental variables such as flooding.

Anna Heikkinen, a researcher at the University of Helsinki, Finland, who was not involved in the study, said the results were consistent with her own research findings from the Mantaro River basin, and the Huaraz region.

“Mining-related contamination in the high Andes of Peru is a serious ecological, socio-economic and health risk for local people,” Heikkinen told SciDev.Net:

She said the study offered a detailed analysis of the different levels of heavy metals and metalloids in the Lake Junín area and the risks they posed to local populations and ecosystems.

“I hope the Peruvian authorities will take such study in serious consideration to protect the well-being of local people, animals and environment,” she added.

The regional environmental authority for the Junín area did not respond to SciDev.Net’s requests for comment on the study’s findings.

This article was produced by SciDev.Net’s Latin America and Caribbean desk.