The average amount of lead in the blood of young children living at Port Pirie has risen nearly 45 per cent in the past year, reaching its highest point since 2010.

Key points: The number of young children with dangerously high levels of lead in their blood has almost doubled

The number of young children with dangerously high levels of lead in their blood has almost doubled A University of Macquarie professor described it as "tragic" for the children of Port Pirie

A University of Macquarie professor described it as "tragic" for the children of Port Pirie SA's Health Minister says without the current lead abatement program the figures would have been worse

The average level of lead in blood has gone from 4.2 to 6.1 micrograms per decilitre (g/dL) compared to the same time last year.

The number of children, aged up to four years old, with dangerously high levels of lead (above 20 g/dL) has jumped from nine children in 2018, to 16 this year.

The results come as smelter operator Nyrstar has just restarted its higher polluting sinter plant after the unexpected shutdown of its modern TSL furnace, due to damage.

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

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

"We've seen an increase in the average blood lead," Dr Simon said.

"That means the number of children who are above 5 g/dL has gone up and most disturbingly I think is the number of children who are above 20 g/dL.

"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."

Professor Mark Taylor from the University of Macquarie said the result was a tragedy.

"It's absolutely tragic for the children in Port Pirie, and I say that with all sincerity, because they can't escape the lead," Professor Taylor said.

"The evidence shows there is no safe threshold.

"You can do all the monitoring you like, and you can have all the programs you like, but if there's dust in the air and lead dust on the ground, those kids are going to be leaded."

Smelter operator Nyrstar has just restarted its higher polluting sinter plant, after the unexpected shutdown of its more modern furnace. ( ABC News: Gary-Jon Lysaght )

Health minister says it is a matter for the EPA

Speaking on ABC North and West SA this morning, Health Minister Stephen Wade acknowledged the seriousness of the increase.

"It's not good enough, and that's why in recent weeks cabinet and the Health Department have been talking about how we can make the best possible effort in lead abatement," he said.

"It's concerning to see an increase, but that just spurs us on to redouble our efforts."

But he said it was an issue for the Environmental Protection Authority.

"I'm delivering the lead abatement program, I'm not managing the EPA, that's a matter for the Environment Minister."

Environment Minister David Speirs was on leave and unavailable for comment.

Mr Wade said he believed the program was effective, despite the increased lead levels.

"Without the current efforts being made the results would have been worse," Mr Wade said.

"We'll be urging all residents of Port Pirie to work with the environmental health team, to reduce their exposure."

The Port Pirie smelter is the city's biggest employer and has recently undergone a $660 million redevelopment. ( Supplied: Marian Martin )

Keith Baldry, the director of science and information at the EPA, said his organisation was responsible for monitoring emissions, but not cleaning up the lead that falls on the ground.

"The EPA's role is to be the regulator of the smelter operations. We can control the emissions from the site," Mr Baldry said.

"In terms of the lead in Port Pirie itself, there is a targeted lead abatement program [TLAP] whose role is to take action in the town to clean facilities or recommend action to minimise the resuspension of dust," he said.

Smelter operator 'surprised' by results

Smelter operator Nyrstar said it was particularly disappointed by the increase, considering recent reductions in smelter emissions.

"[For] the second quarter of 2019 lead-in-air performance is the best year-to-date lead-in-air performance since 2015," the company said.

"The reported deterioration in children's blood lead levels as outlined in the 2019 Q2 SA Health Port Pirie Blood Lead Level report is particularly disappointing and surprising.

"Nyrstar is continuing to increase its already significant focus on implementing initiatives to further improve its lead-in-air and environmental performance."