Copper producer Antamina has been fined for a toxic spill that left hundreds needing medical treatment. Critics have condemned the US$77,000 penalty as extremely low by international standards.

Antamina is the world’s third largest copper producer, owned by international firms including BHP Billiton and Xstrata.

The toxic slurry spill occurred in July 2012 when a pipeline burst in the northern highlands of Cajacay, Ancash. More than 350 local residents, among them dozens of children, suffered symptoms including vomiting after inhaling toxins from the 45-ton spill.

Peru’s environmental authority (Organismo de Evaluación y Fiscalización Ambiental) announced the fine on 3 June. The penalty was imposed for “the lack of diligence in the reporting of the accident” and the need to fell trees affected by the pollution, according to environment minister Manuel Pulgar-Vidal.

Civil society groups have condemned the fine as too small. They pointed to the $11 million fine paid in Chile by Canadian company Barrick Gold for failing to build water management systems before beginning extraction at its Pascua Lama project.

Last year Pulgar-Vidal had predicted the Antamina fine could reach $13 million. He has blamed legislation for the limited size of the actual fine. He added that subsequent legal changes mean similar incidents in the future would be more heavily penalised.