Sayuri Moreno found out while pregnant that her body was contaminated with arsenic, but could not afford doctors’ advice to avoid breastfeeding and leave her home in a mining area in northern Peru.

The 37-year-old is one of 120 residents of the Huarmey slums in the Ancash department who were found to have high levels of arsenic in their blood when 140 people were tested last year, according to the Ministry of Health.

Some 3,000 live in this community of wooden houses facing the sea, most of them living off fishing. Behind the settlement rise the hills through which underground pipelines descend, transporting copper and zinc concentrate to Port Huarmey.

Arsenic – a highly toxic chemical – can be found naturally alongside copper ore and is released as a byproduct of its processing. Arsenic can also naturally contaminate groundwater.

Peru is the world’s second-largest copper producer, however health authorities say they have yet to determine whether the widespread contamination in Huarmey is linked to mining operations.