Since July 2020, elevated levels of lead in drinking water at Waikouaiti, Karitane and Hawkesbury had been recorded, which led to a protracted public health response, including blood testing of residents, after the news went public last February.
An investigation was conducted, which found the likely cause was lead leaching from pipes and fittings at the point of supply.
The Ministry of Health recommends that people flush two cups of water from cold taps before consuming it.
A paper written by Dunedin City Council plant operations manager John McAndrew, Environmental Science and Research toxicologist Dr Belinda Cridge and Tasman District Council water quality and safety specialist Rosemarie Nelson was published ahead of this week’s International Lead Poisoning Prevention Week.
The paper included computer modelling of the Waikouaiti incident. The model showed blood lead levels were only minimally affected by infrequent spikes of lead contamination in water.
However, it could not draw any conclusions about the amount of lead retained in bones, where it has a half-life of up to 30 years.
Master Plumbers, Gasfitters and Drainlayers New Zealand chief executive Greg Wallace said research had made it clear there was no safe level of lead in drinking water systems, but New Zealand allowed lead to be used in plumbing products.
Consultation by the Ministry of Business, Innovation and Employment was happening, and it was likely that all new plumbing fixtures would have to be lead free by 2025.
The country still had lots of water infrastructure made up of old cast iron pipes which had lead joints and needed to be removed, Mr Wallace said.
"We know that there’s lead leaching that's occurring," Mr Wallace said.
"To be honest, this has all been too slow.
"The reality is that asking people to flush their taps every morning doesn’t happen."
There needed to be mandatory testing for water suppliers across New Zealand for lead levels, Mr Wallace said.
