You don't need to be a meth head or sympathise with their stupidity to celebrate Sir Peter Gluckman's report on the risk they pose to houses. At long last someone has brought a sense of proportion to a question of public health and safety.

Gluckman has defied the excessive caution that rules so much of our lives today, casting aside the precautionary principle that says a lack of evidence of harm does not prove something is safe.

The Government's Chief Science Adviser has given Housing Minister Phil Twyford the finding Twyford wanted, enabling more state houses to be kept tenanted, but it was courageous nonetheless. Not because he has threatened the business of fumigating firms, those pose no risk to his reputation, unlike fellow scientists who assiduously promote the precautionary principle.

The morning after his report was published, an Australian professor was on the radio complaining that the report ignored case studies she had given him showing health effects from meth residue at lower levels than he was recommending as a threshold for concern. Gluckman replied that her studies were of houses used to cook the stuff, he was talking about the residue from smoking it.

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If his report was refreshing to read, it was mild by comparison with the enthusiastic response from the Green Party, usually committed to the precautionary principle. "Hundreds of people have been unnecessarily turfed out of state homes and other houses because of scaremongering by people with vested interests," fumed co-leader Marama Davidson. "This has caused so much hardship for so many families with no good reason....."

It reminded me of those ridiculous beach warnings Aucklanders were given last summer after every rainy day. Suddenly a 40-year-old occasional problem was elevated to a major health risk posted on beaches around the region advising us not to swim.

When I questioned those warnings, a marine scientist explained the notices were posted when pollution was at a level at which 2 per cent of swimmers on average would become ill. That would amount to hundreds of cases on a summer weekend. Strange we did not hear of gastro outbreaks on that scale before the age of excessive precautions.

What chance the Chief Science Adviser might check whether that risk warrants beach closures? Or whether rivers need to be of "swimmable" quality? Or the risk plastics really pose to fish, or the need to ban so-called "single use" supermarket bags that serve so many secondary uses in our house I don't know what we'll do without them.

Back in March the Economist took a good long look at the problem of discarded plastic. It noted salt water and sunlight reduces a great deal of it to microscopic compounds that can be ingested by fish. Much of the rest is swept by currents into mid-ocean "gyres" which are not particularly rich in fauna or biodiverse.

"No studies have so far been performed to test whether toxins [microplastics absorbed by fish] concentrate up the food chain," it said. The only evidence of them entering the human diet involved mussels which are eaten whole. It didn't say whether the diner survived.

The article also said the manufacture of plastic releases much less carbon dioxide than some of products proposed to replace it. A British study had found "a cotton tote bag must be used 131 times before greenhouse gas emissions from making it and transporting it improve on disposable plastic bags. The figure rises to 173 times if 40 per cent of the plastic bags are used as bin liners..... The carbon footprint of a paper bag that is not recycled is four times that of a plastic bag."

So much is becoming regulated, restricted or taxed today in a way that is out of all proportion to the risk it presents. It's being done in the name of impossible puritanical targets, Smokefree NZ, zero waste, net zero carbon emissions....

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When the target year gets near enough to see that it will not be reached, it becomes a cue for more extreme measures. Smokefree 2025 now wants health warnings not just on tobacco but on e-cigarettes which do not produce smoke. They do not burn leaf and leave tar in the lungs.

Gluckman has said of methamphetamine smoke residue, "No data have been reported related to third-hand exposure situations.... To the best of our knowledge there is current no available evidence that low level methamphetamine exposure poses a health risk to humans."

That sort of scientific caution is usually a cue for health and environmental zealots to urge that nothing be done until a risk is completely ruled out, knowing science can seldom do that. But this time they like the conclusion and they want vengeance for Housing NZ's previous precautions.

When they look for blame hand them a mirror.