The number of children with "harmful" levels of lead in their blood in the South Australian regional city of Port Pirie has more than doubled since 2017.

Key points: SA Health says an upgrade to the lead smelter has led to increased lead levels in the air

SA Health says an upgrade to the lead smelter has led to increased lead levels in the air Lead exposure has been shown to affect children's intellectual development

Lead exposure has been shown to affect children's intellectual development The company says emissions should reduce once the new plant is fully operational

New SA Health data has shown average lead levels in children tested over 2018 had jumped nearly 5 per cent compared to the previous year, sparking concern for children's development.

SA Health director of scientific services, Dr David Simon, said an upgrade of the Port Pirie lead smelter had increased lead levels around the city.

"Our children have been exposed to a higher level of lead in the last year or so than they have previously and consequently we've seen this increase in blood lead," he said.

Lead exposure has been shown to affect children's intellectual development, preventing the brain from growing to its full potential.

Dr Simon highlighted the numbers of children with lead-in-blood levels above 20 micrograms per decilitre, a level the National Health and Medical Research Council considers "harmful".

"It is very concerning seeing the number of children who are spiking above 20," he said.

"Average results for two-year-old children, which are considered to be a robust indicator of trends in lead exposure for the whole population, [are] 3.6 per cent higher than 2017."

SA Health says the lead smelter upgrade has increased lead levels around the city. ( Lauren Waldhuter )

He said there were a range of reasons for the increase.

"The redevelopment, which is really hard to do without causing a lot of dust, has contributed to lead being distributed throughout the community," he said.

"But Port Pirie also had its driest year in about the last 10 years, which has resulted in more lead dust in the air."

What is being done?

Dr Simon said there had been a number of extra measures taken to protect children from lead since increased lead-in-air readings in Port Pirie last year.

"We are working very closely with those families to identify those sources and help families try to reduce the exposure," he said.

An additional social worker was also employed to better target at-risk families late last year.

The Targeted Lead Abatement Program (TLAP) — jointly funded by Nyrstar and the State Government — works with SA Health to mitigate lead in the community.

TLAP spokesperson, Associate Professor Rob Thomas, said a new community awareness campaign to remind residents of the importance of reducing lead exposure around the home had begun.

Interventions such as childcare away from lead exposure, assisted cleaning in the home and help in forming lead-safe habits are part of the services.

"TLAP has also intensified its activities recently including increasing daily cleaning of high-use community amenities, replacing old bark chips at public playgrounds, expanding the reach and frequency of its cleaning roster in high-risk areas," he said.

'Levels still too high'

A major upgrade of Port Pirie's smelter completed last year was supposed to radically reduce lead emissions.

But as the new plant was tested alongside the old one, smelter owner Nyrstar found itself on track to breach its cap on air-lead levels.

Company executives ordered a six-week shutdown as well as company-wide cleaning activities.

"Unless we all make a change to the way we operate … the potential for us to breach the limit will become a fact," the company wrote in emails seen by the ABC.

The strategy worked, and the company narrowly avoided breaching the smelter's licence limit of 0.50 micrograms per cubic metre for the December quarter.

The company says emission should continue to fall this year following the upgrade. ( ABC News )

Nyrstar said it was committed to continuing to lower lead emissions in Port Pirie, and has maintained once the new plant is fully operational sometime this year, emissions should drastically reduce.

"The strategies and actions that were used to successfully reduce emissions of lead-bearing dust since October 2018 will continue to be implemented across the site and will deliver a much improved lead-in-air performance in 2019," the company said.

But Environment Protection Authority [EPA] director Keith Baldry said there was more work to be done.

"The levels are still too high and we continue to work to ensure the company does everything possible to reduce its emissions while it transitions to new smelting technology that meets modern emissions standards," he said.

Blood level decrease will 'take some time'

The company maintained emissions from the redevelopment had peaked and should continue to fall this year.

"Nyrstar is confident that the period-to-date lead-in-air concentration at Pirie West Primary School will be under the compliance limit as required at the next quarterly assessment on the 31st March 2019," the company said.

Dr Simon said while child lead-in-blood levels should drop with environmental lead levels, it wasn't quite that simple.

"When a person is exposed to lead it takes quite some time for that lead to be cleared from the body even if we stop the community from being exposed," he said.

"The entire community of Port Pirie has been exposed to air dust and it's going to take considerable time for that to be removed."