Two chemical leaks from metals processor Nyrstar have made their way into Port Pirie's groundwater and a waterway over the past two years, an ABC investigation can reveal.

Key points: Two chemical leaks have occurred at Port Pirie's Nyrstar site since 2017

Two chemical leaks have occurred at Port Pirie's Nyrstar site since 2017 There have been reports of fish kills from locals

There have been reports of fish kills from locals One expert says Nyrstar must be more transparent and accountable for the environmental management of its smelter

The Belgium-based company admitted a sulfuric acid leak occurred in January this year, following questions raised by the ABC over allegations that mass fish deaths had occurred in a breeding ground near the factory site.

"The incident occurred following the failure of a valve and ultimately resulted in a discharge into the water course," a statement from the company said.

"No persisting environmental impact was observed. Nyrstar has subsequently implemented new processes and alarms."

Documents from the state's Environmental Protection Agency (EPA), released under Freedom of Information, show sulfuric acid leaked from Nyrstar's factory into Port Pirie's First Creek on January 31.

The EPA refused to release a summary of the incident, however February briefings to South Australia's Primary Industries Minister Tim Whetstone said "localised fish kills" had occurred in mangroves, with State Government investigators unable to assess the damage for at least five days after the spill.

Parliamentary briefing notes were prepared for ministers and media statements were prepared, but no public announcement was made.

Net fisherman David Wilkes wants greater transparency over operations at Nyrstar's smelter. ( Source: Shuba Krishnan )

Toxic leak occurred in 2017

The ABC can reveal another potentially more hazardous chemical leak occurred in 2017, where cadmium was detected in groundwater, with the EPA tracking it to a "potential source in a chemical storage area on site".

Cadmium is a highly-toxic metal that is produced during the smelting of other metals.

It triggered a Section 83 notification under the state's Environmental Protection Act, which means there was serious environmental harm caused or threatened to occur.

The EPA said following the detection of the leak, Nyrstar removed all chemicals from the area and "undertook remediation action".

However, it said the amount of cadmium leaked from the site was "unknown".

The EPA confirmed it did not release information to the public following the cadmium spill or the sulfuric acid spill as they were "ongoing investigations".

Drinking water for the town is sourced from a treatment plant, not from groundwater.

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Local net fisherman David Wilkes, who reported the January sulfuric acid leak, said the smelter was important to the town, but called for greater transparency to ensure the environment was kept clean.

He said both leaks had been the subject of discussion in the community, but there had been no formal notification from the State Government or Nyrstar.

"The marine environment is important to us, as a community and myself personally because it affects my livelihood," he said.

"When these sorts of things happen, I think it's the responsibility of the smelter to let the public know exactly what's going on, what the consequences are and what remedies have been made to fix the situation."

Environmental health expert Mark Taylor has warned about Nyrstar's long-term impacts on human health. ( Source: Greg Heap )

'I wouldn't eat fish caught there'

Macquarie University environmental health expert Mark Taylor said news of the leaks was "seriously concerning".

"It leads us to ask questions about the quality of the environmental management practice and due diligence on the site," Professor Taylor said.

"We know that they've recently had further emissions from the old smelter … the new smelter stopped working, and we also know that they've had very high emissions to the environment and children's blood lead [levels] has spiked recently.

"There's a raft of problems associated with that facility and it needs very careful inspection in order to mitigate those risks and we need to ask what's been done about it."

He said there was a moral duty, if not a legal duty, to inform the community.

"Quite frankly, I wouldn't be eating fish from around Port Pirie, because we know there's a huge burden of metals coming from the plant both in terms of dust and rainfall runoff," he said.

"That gets into the food chain, that gets into seagrasses … and we also know it gets into fish and marine life.

"These metals are elemental — they don't go away, they bioaccumulate and they're toxic."

Lead emissions spiked in 2018 and 2019 in the wake of the smelter's redevelopment. ( SA EPA )

Turbulent times for Nyrstar

Nyrstar has been through a turbulent couple of years, amid global financial difficulties, the death of a worker in Hobart, and technical problems surrounding the $514 million upgrade of the Port Pirie smelter.

The company was on the brink of bankruptcy before global commodities trader Trafigura stepped in to raise its stake to 98 per cent from 24.4 per cent.

On October 12, it was revealed minority shareholders planned to sue Trafigura for $1.63 billion in damages over the restructuring of the Belgian company done under the terms of a deal to save the company.

The Port Pirie smelter, which has been in constant operation for more than 127 years, processes lead-rich concentrates and smelting industry by-products.

The local community relies on the smelter for employment, but the flow on impacts of emissions to human health have long been a concern.

Pressure to reduce lead emissions and increase productivity prompted the company to upgrade the smelter, with the loan underwritten by the State Government.

Voluntary blood testing for children is conducted every quarter. ( ABC News )

The new metals processing plant was opened in January, but problems have since forced the smelter to shut down twice.

It forced Nyrstar to reopen its old sinter plant, known for its higher lead-in-air emissions.

A 2018 sustainability report released by the company found sulphur dioxide emissions had increased by 16 percent over the year, with 97 per cent of these emissions coming from the Port Pirie smelter.

The report also said lead emissions did not meet expectations, with "several emission events" contributing lead-bearing dust over the local community.

In August, regular testing of young children in Port Pirie found the average amount of lead in the blood had risen nearly 45 per cent in the past year, reaching its highest point since 2010.

In releasing the results, SA Health's director of scientific services Dr David Simon said the increase had been across the board.

"Just remember this is the half-yearly report so we've only tested half the children, but we expect that trend to follow through for the whole year," Dr Simon said.

Lead is a toxic heavy metal, with long-term exposure in children associated with reduced growth, learning difficulties, behavioural problems and reduced IQ.