At almost 3,800 metres one should be able to breathe fresh and clean air. Yet as soon as you get close to the town of La Oroya, in a valley in the central Peruvian Andes, coughs, crying eyes and a constant metallic taste will tell you otherwise.

The surrounding peaks have lost their green colour, leaving bare rock. In the middle of the valley, a huge chimney of about 200 metres emits fumes with high concentration of arsenic, lead and cadmium from the local smelter.