Standards New Zealand "stands by the process" that saw vastly too conservative meth limits set.
As a result of the limits, people were moved out of homes and were often lumped with the cost of testing and decontaminating the home.
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The limits set by Standards New Zealand were an attempt to sort out the misuse of guidelines set by the Ministry of Health in 2010.
Those guidelines were intended as a clean-up standard for meth labs. Before clean-up, meth labs would be expected to have a reading above 30 micrograms, a report from the Sir Peter Gluckman says. They should be cleaned to the level of 0.5 micrograms per 100cm2, the Ministry of Health recommended in 2010.
The manufacture of meth involves additional chemicals not found in the smoking of meth, so houses must be cleaned to a higher standard.
But Housing New Zealand used those guidelines on houses where meth had only been smoked. The Ministry of Health says it told Housing New Zealand a number of times it was using the guidelines incorrectly. Housing New Zealand told RNZ this morning it has no record of that communication from the Ministry of Health, though the Ministry of Health also voiced its concerns to media at the time.
The limit of 1.5 set by Standards New Zealand in 2017 was an improvement on the guidelines for lab cleaning - it tripled it. But the standard was still far too conservative. As a result, people continued to be needlessly removed from homes safe to live in.
The hugely significant report from the Prime Minister's chief science advisor released last week said there's no evidence residue left on housing by typical meth smoking causes health problems. He recommended the limit should increase to 15 micrograms.
Carmen Mak from Standards New Zealand says the agency stands by the process by which the 1.5 standard was developed.
The standard was developed by a "balanced committee of technical experts," Ms Mak told Mark Sainsbury on RadioLIVE.
"We stand by the process by which the standard was developed... That is the role of Standards NZ."
That committee was criticised at the time of its inception, because the 21 member group included people from the meth testing agency. It also included the insurance sector, property managers, local and central government (including the Ministry of Health and Housing New Zealand) and laboratories.
Ms Mak pointed to a key piece of evidence used to inform the panel who set the standard.
"We are not experts in the science. That's why committee has access to that ESR report commissioned by the Ministry of Health," she said.
In 2016, the Ministry of Health asked ESR to independently review the guidelines and provide advice. That report was then used to inform the Standards New Zealand panel.
The ESR is New Zealand's Crown Research Institute that specialises in science relating to people and communities.
Sir Peter told Sainsbury he and his team went through the data extensively.
"The science is the science is the science," he said.
"Everything in life involves understanding relative risk and proportion. Here we've got a situation where the risk is very, very low."