Meth myth: 1338 state homes decontaminated in two years - almost all needlessly

Housing New Zealand says in two years, 1338 state houses were decontaminated for meth - an exercise that would have been completely needless in almost all cases.

Most of the decontaminated state homes were in Auckland and Wellington - two centres that have experienced well-documented housing problems, including stubborn waitlists for state housing.

Figures provided to Newshub by Housing NZ show over three years, 488 homes in Auckland - where the house crisis is most acute - were decontaminated.

And that's just the state houses - that figure would be much higher if social housing and private rentals were included.

The cleaning of a house that tests positive can cost between $2000 and $50,000 or more.

A report from the Prime Minister's chief scientist Sir Peter Gluckman on Tuesday found no evidence of negative health effects associated with non-users living in houses where meth was previously smoked. That means millions were needlessly spent cleaning state houses while people waited for homes.

The Ministry of Health told Newshub from 2010 to 2016 it "routinely pointed out" to Housing NZ it was using the wrong standard - a standard for cleaning former meth labs, not dwellings where meth was previously smoked. The standard at the time was 0.5 micrograms.

The manufacture of methamphetamine can involve additional toxic substances, so those properties need to be cleaned to a much higher standard. The detection of meth is used as a proxy for the detection of other toxins in those properties.

That standard for a dwelling where meth was smoked rose to 1.5 micrograms in June 2017 - a standard the Ministry of Health helped deliver. When the new standard was released, the Ministry said "this new standard provides appropriate public health protection."

But it was still much too conservative, meaning houses were needlessly cleaned and private and state house tenants moved on when their houses were still safe. The standard is now 15 micrograms, though Sir Peter said he'd be comfortable with a toddler crawling around licking surfaces with 100 micrograms of methamphetamine present across 100cm2.

Housing NZ says the number of decontaminated houses does not equate to the number of terminated tenancies, and it certainly doesn't equate to the number of evictions.

Housing NZ told Newshub 18 houses were evicted due to meth or other drug activity in three financial years, and said most other tenancies where meth was found would have been relocated.