How safe are meth houses, really? And what's it like to go inside? Katy Gosset and Alison Ballance take the plunge and ask how much meth is too much when it comes to setting a national standard?

Meth houses have been in the headlines lately.

Housing New Zealand has been heavily criticised for using Ministry of Health guidelines designed for clandestine meth labs, to assess homes where the drug has merely been smoked.

And the Ministry of Health has just released new interim guidelines for properties where meth's been used

But debate continues as scientists try to pin down how much harm meth residues can cause.

Standards New Zealand is now working on a new national standard with a draft due out for public consultation in November.

The Science of... hears from the Ministry of Health, Massey University toxicologist, Nick Kim, and Environmental Risk Assessor, Jackie Wright.

And the team gets first hand experience of a meth house alongside the drug testing firm, MethSolutions.

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What is snow? How and where is it made? Why is it white? Alison Ballance and Katy Gosset head to Mt Ruapehu in search of the answers to all your questions about snow.

Alison Ballance straps on her skis and her sound recorder, and heads to the slopes of Mount Ruapehu in search of some snowy answers.

Along the way, Alison and co-presenter Katy Gosset learn about the snow-making factory high in the sky, about the snap-freezing properties of super-cooled water, how snow flakes are always six-sided and why New Zealand gets wet, heavy snow.

Their guide on the ground is snow man Brendon Nesbit, who lives and breathes snow. When he's not forecasting avalanches and heading the ski patrol on New Zealand's Turoa ski field, he is doing the same job at a ski resort in Utah, in the United States.

The avalanche forecasting job involves constantly monitoring the weather and the winter snow pack on Mt Ruapehu. Every day, Brendon and his team are digging, poking, prodding, taking the temperature and even tasting the snow on the ground to understand its properties. Their aim is to make the ski field and its users safe from avalanches.

Meanwhile, back in Wellington, Metservice extreme weather forecasters Erick Brenstrum and Gerard Barrow have their eyes on the sky. Is there snow forming? Is it cold enough for it to reach the ground or will it melt to rain on the way down?

They explain how snow begins life as a tiny ice crystal, created when water gas freezes around a tiny bit of dust or even bacteria. And they explore the differences in snow weather, between a southerly outbreak and a northerly over-running situation, and what effect that has on the ground.

And NIWA's Christian Zammit points out that snow isn't just of interest to skiers - melting snow supplies water to farms and towns, and also produces most of New Zealand's hydro-electricity.

Check out the Eyewitness podcast on the Everest avalanche, to find out what it's like to witness a large avalanche with many fatalities and injuries.

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Simon Morton and Alison Ballance present a three-part series exploring the science of sweat, virtual reality and Vitamin C. This week, the function of a much-maligned bodily fluid that plays a vital role in keeping us humans healthy and alive.

Human sweat - 99 percent water with a dash of salts and a pH of around 4.5, is a much-maligned bodily fluid that plays a vital role in keeping us humans healthy and alive.

The word's become shorthand for hard work and discomfort but without it human life just wouldn't be the same: if our prehistoric ancestors hadn't been able to sweat they could never have stayed cool for long enough to chase down their prey on the ancient Savannah.

What happens when we sweat?

People sweat for all sorts of reasons; emotional sweating when we're stressed, scared or in pain, or the sweat we get on our forehead when we eat spicy foods. There's the night sweats that people suffer during menopause, and the sweating people experience when they are withdrawing from drugs.

But the most common encounter we have with sweat is for thermo-regulation, for cooling us down when we get too hot running for the bus, in humid weather, or when we exercise. When we heat up, the hypothalamus in our brain detects that our body and skin temperature is rising and using a neurotransmitter called acetylcholine it sends a signal to stimulate millions of eccrine sweat glands to release a salty liquid- sweat- via ducts onto our skin to evaporate and cool the body down.

These eccrine glands are spread out over most of your body but you have higher concentrations on the palms of your hands, the soles of your feet, your underarms and your forehead. The sweat from these eccrine glands is mostly water and salt and doesn't tend to smell.

There's another type of sweat gland called the apocrine gland that can be more problematic. These glands are concentrated in the underarm and groin and from puberty onwards secrete a more oily sweat full of proteins and lipids when you get hot or stressed out and anxious. Although apocrine sweat is sterile when it hits the skin's surface, the bacteria living on you love to eat this gooey goodness, and then excrete the volatile compounds that we sniff as body odour.

The role of our microbes in making us smell

"Hot and humid, the armpit populated by bacteria cursed with creating a noxious odor. That smell, however, has proved lucrative. Today more than 90 percent of Americans use some sort of armpit cosmetic, creating a worldwide deodorant bonanza worth $18 billion." Terrence McCoy in The Washington Post…

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