Top scientist explains how we got meth testing so wrong

New Zealand's meth testing standards have been condemned by a new report.

The regime has seen people needlessly evicted from homes, and millions of taxpayer and private dollars wasted, a report yesterday concluded.

The report wasn't put together by just anyone. It was the work of the Prime Minister's Chief Science Advisor, Professor Sir Peter Gluckman. He's been in the role since 2009 and is moving on in two months.

The report will have knock-on effects. Will landlords who trusted the standard and spent tens of thousands industrially cleaning their homes just have to stomach it? The Government says it won't be compensating them. And there are calls for tenants who were evicted from state housing to be compensated.

So, how did we get here?

Sir Peter says New Zealand adopted a standard meant for the cleaning of meth labs, not for premises where meth was smoked. The two are very different. We were the only country in the world to use the standard in this way.

"Somewhere along the line, the standard for cleaning up a meth lab was transferred in New Zealand - but nowhere else - to assuming all houses have to be cleaned to that level," Sir Peter told Mark Sainsbury on RadioLIVE.

"The rationale for cleaning a meth lab is very different to the scientific and medication rationale about looking elsewhere."

In his report, Sir Peter says there can be other contaminants present in meth lab. Testing for meth itself is a good indication of how many other toxic substances there might be. That's why the figure is so conservative - in other countries, substances like mercury have been used in the production of meth. His report says there's no evidence of that particular highly poisonous substance being used in New Zealand.

Sir Peter says there was simply no evidence the typical amount of residue left on household surface in a home where meth has been smoked posed a health risk.

"We were somewhat surprised - the more we looked into it, the less the evidence that passive exposure to surface levels of methamphetamine existed. We could find no compelling case of such an example."

In typical science fashion, he laid his argument out in three steps.

"The evidence is number one, it's a horrible drug and no one should be using it but sadly people do.

"Number two, in premises it has been manufactured there is risk associated with the manufacture.

"Number three is, the kinds of levels seen in New Zealand homes after testing are not sufficient to justify a) spending the money on testing and b) spending the money on remediation."

As a result of yesterday's report, 240 state houses that are currently empty will be released within weeks.

Housing New Zealand (HNZ) will now use a new standard of 15 micrograms of meth detected per 100 square centimetres after cleaning, expecting to save $30m a year in remediation and testing. That's 10 times the current limit of 1.5 micrograms and 30 times the limit that was in place before that.

Ross Bell from the NZ Drug Foundation says the previous Government was warned meth contamination fears were overblown but "chose to take no action."

National's social services spokesperson Paula Bennett says she "fought back pretty hard" against the standard but was told it was "inappropriate" to try to direct Housing NZ's health standards.