In 1984-1985, the Swedish metal company Boliden Mineral AB paid a local mineral extracting company, Promel Ldta., 10 million SEK ($1.2 million, $3.15 million in 2021 dollars) to receive, treat and confine around 20,000 tonnes of smeltery sludge from Rönnskärsverken in Skellefteå, containing among other things high levels of lead, arsenic, cadmium, mercury and iron and smaller amounts of gold and silver. To earn additional income, Promel planned to extract various substances from the waste at its processing plant at Sitio F in the outskirts of Arica. The end products were mainly raw arsenic and iron-silver-gold oxides. The first shipment arrived in Arica in August 1984 and the processing of 500 kg test batches in October 1984 gave positive results with oversight from an official from the Chilean Health Authority in Santiago. After the sludge processing had begun at large scale and the third and last shipment of sludge arrived to Promel's plant in Arica in July 1985, contact between Boliden and Promel ceased.
