Toxic metals contaminate Lake Junín basin ^{CEFR B1}

Researchers from the National Institute of Agricultural Innovation of Peru and the National University Toribio Rodríguez de Mendoza analysed more than 200 surface soil samples taken around Lake Junín, also called Chinchaycocha. The basin sits at 4,100 metres above sea level, is the second largest body of water in Peru and feeds the Mantaro River. The team measured 14 heavy metals, metalloids and trace elements and used grid sampling points and machine learning together with environmental variables such as flooding.

The study found that 99 per cent of the area has "very high to ultra-high" ecological risk. It reports a "100 per cent carcinogenic risk" for adults and highlights that children are highly exposed to arsenic. Samuel Pizarro, one of the authors, said: “The levels of arsenic are extremely high, as are those of lead and cadmium, far exceeding acceptable thresholds.” He also warned that chromium levels pose a serious threat to health.

Researchers note a bioaccumulation process: animals eat contaminated fodder, which affects local food and exposes people who use the land and water. They link local contamination to mines abandoned for a century or more, plus agriculture and urbanisation. The basin has a mining tradition dating back more than 300 years and acts as a sink for metals in water, sediments and grazing soils.

The area directly hosts about 50,000 people in urban and rural communities, and the authors say the impact reaches 1.3 million people because some water is used downstream in valleys and in dams. The team calls for further work to calculate the full size of the impact and the effects on children and pregnant women. A researcher not involved in the study, Anna Heikkinen, said the results match her work and called mining contamination a serious ecological, socio-economic and health risk. The regional environmental authority for Junín did not respond to requests for comment.