The Ministry of Health dismissed concerns the meth testing standard was unnecessarily stringent, documents show.
People have been evicted from private and Housing NZ homes, with millions of private and taxpayers' dollars wasted on unnecessary cleaning, a report fronted by the Prime Minister's Chief Science Advisor Peter Gluckman found in May.
The critical error had been treating homes used for the manufacture of meth as equally dangerous as homes where meth was only smoked. In reality, there are far more dangerous chemicals associated with manufacture.
In the documents released to Newshub, the Ministry of Health says meth would be smoked but not manufactured in 98 percent of homes where meth was detected.
Just one reference to concerns the standard was too conservative was turned up in a request for all advice and briefings provided by the Ministry of Health from 2008 until 2017.
The query was raised by then-Minister for Social Housing Alfred Ngaro in May 2017. He wanted to know about a "considerable number" of concerns that had been raised about the standard.
The Ministry of Health informed him there was "general support" for the standard, but that some had argued the level should be relaxed. Others raised concerns about eviction, the cost of decontamination and the loss of possessions.
Those concerns were dismissed.
"The Drug Foundation argued strongly that the level should be relaxed, but their scientific advisor didn't provide the evidence to support his advice when he spoke to the committee," the Ministry of Health said.
"The Community Housing Group, aligned with an Otago University Researcher, provided a paper but [the Environmental Science and Research] ESR's scientists reviewed the paper and found it didn't change his risk assessment," the emails say.
The Drug Foundation's chief executive Ross Bell said the Foundation argued New Zealand should only use a standard for properties where meth was manufactured.
"Our submission said you can't come up with a standard for meth use" because there wasn't the science to back it up, Mr Bell said. He said the submission was in writing, not at the committee.
There's no evidence of questioning from other ministers captured in the information request.
The emails also show disagreement among the Standards NZ committee, with "ongoing discussion" in November delaying the release of the draft standard.
The November discussion was over whether there should be only one flat standard or different standards in homes where meth had been smoked as opposed to manufactured.
The Ministry of Health and Housing NZ initially sought the adoption of a three-level standard instead of a flat rate.
A sternly worded email in November 2016 sent by Stewart Jessamine, the acting director of the Ministry of Health, says the Ministry of Health and Housing NZ raised "strong objections" to the flat 1.5µg/100cm2 standard.
The same concern was voiced by Paul Prendergast, Principal Public Health Engineer at the Ministry of Health.
He wrote in an email the extra costs associated with the 1.5µg/100cm2 standard would be "millions of dollars per annum," affecting about 7 percent of contaminated properties.
One of his issues was "unnecessary levels of cleaning of houses that are uncarpeted or have contaminated carpet removed."
Evidentially won over six months later, there was something close to consensus on the 1.5µg/100cm2 standard, with just two votes against, both from the meth testing industry.
"The committee members who have voted negatively are a scientist from a sampling and testing firm, a property manager and a decontamination contractor. The sampling and testing firm is unlikely to vote positively for the standard," the June 2017 briefing says. It says issues were resolved with the property manager and the vote was 19 to 21 in favour.
Another year on, and the 1.5µg/100cm2 standard was blown out of the water.
The chief science advisor concluded exposure to meth levels below 15 μg/100 cm2 would be highly unlikely to cause any adverse effects in homes where meth had been smoked but not manufactured.
He recommended an end to the testing of homes where meth was smoked, unless it had been used at unusually high levels.
Housing New Zealand (HNZ) will now use a standard of 15µg/100cm2
after cleaning, expecting to save $30m a year in remediation and testing.