This Way Up for Saturday 12 August 2017

The science of sweat, insuring nature against damage, and voluntary carbon offset schemes: (how) do they work?

The Science of... Sweat

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.

Armpit swabbing

Armpit swabbing Photo: (Credit Matt Zeher)

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

It's tough to talk about sweat for any length of time without acknowledging the way it smells (thanks apocrine sweat glands!) and the challenges brought about by body odour. And our embarrassment and sensitivity around the subject comes with a hefty price tag attached. Deodorants and antiperspirants, the first line of defence for most of us, form an 'armpit cosmetics' market  worth an estimated NZ$25 billion annually. 

But the truth is that nobody's exactly sure why one person might smell worse than another. The only thing that is clear is that it's a whole lot more complex than the simple question of whether you remembered to use deodorant this morning! And as with just about everything nowadays, there seems to be an important microbial component in all of this. So work is focussing on our microbiome - the bacteria living on us and in us - to explain our problem with body odour, and even to offer solutions for it.

Chris Callewaert of the University of California San Diego calls himself Dr Armpit, he's sniffed thousands of other people's 'pits, and according to Chris there are more bacteria in your armpits than there are humans on this planet. And all of these billions of bacteria are not the same. 

"The higher the diversity in the armpit is, the more chance of having body odour." Chris Callewaert (aka Dr Armpit) of the University of California San Diego

Our armpit ecosystem has up to 200 different types of bacteria but two dominant types. According to Chris, it is the relationship and the balance between the two that can determine whether we have smelly armpits or not. In one corner staphylococci, a genus of gram positive bacteria with about 40 different species; these don't make much of an odour. The more problematic ones are called corynebacterium, these are the beasties that feast on the fats and amino acids in our sweat excreting these volatile compounds that have the unmistakable and pungent tang of body odour.

"If you have corynebacterium, so the bad one, he doesn't come alone and he brings along a whole bunch of friends which cause more body odour."  Chris Callewaert

Basing his work on the study of a pair of identical male twins who smelt very different and had very different armpit microbiomes. He's now trying out microbial transplants between one person and another. So he swabs and cultures bacteria from a 'pleasant' armpit and then transfers this bacteria to a not so fragrant armpit, so far with promising results.

"We immediately saw an improvement in body odour that lasted for a long time, even up to a year after the transplant we still had the good bacteria so that was the first successful case of an armpit transplant and the basis for further investigation". Chris Callewaert

How fabrics hold onto smells... and release them

Do you have a shirt that seems to smell a little bit worse than everything else in your wardrobe? Perhaps it's an artificial fabric, like polypro or polyester whereas other wool or cotton clothes you wear just never seem to smell as bad. 

Another front on the war against sweat - and the odours it can bring - is being fought on our fabrics. A huge market in gym and outdoor wear has sprung up offering us specially designed fabrics that claim to wick sweat away from the skin, lock in smells, or incorporate anti-microbials like silver particles, Triclosan and quaternary ammonium compounds to help neutralise nasty niffs.

Tobi Richter and Raechel Laing of the University of Otago are studying the absorption and release of volatile odour compounds in three fabrics- polyester, cotton and wool

Tobi Richter and Raechel Laing of the University of Otago are studying the absorption and release of volatile odour compounds in three fabrics- polyester, cotton and wool Photo: (Supplied)

At the University of Otago in Dunedin, Tobi Richter is studying the absorption and release of volatile odour compounds in three different fabrics - wool, cotton and polyester - to better understand how smells build up on our clothes and how to reduce them. 

He's discovering that cotton tends to absorb few of these compounds in the first place. But although wool does absorb them, it is then far better at holding onto these smells than polyester. He speculates that this can be explained by the fact that wool is a complex structure with more binding mechanisms than man-made fibres.

"For polyester there was an increase in volatile compounds so that explains why, if you leave your sports gear in a bag for a couple of days, it starts to smell quite strongly" Tobi Richter, University of Otago

Can you really sweat like a pig?

Adults can sweat at rates of several litres an hour, and up to 14 litres per day. Can our porcine cousins really beat us in the sweat stakes?

According to Nick Cave, Associate Professor in Small Animal Medicine and Nutrition at Massey University, almost all mammals sweat to cool down. For example, dogs pant to lose body heat via their mouths. Pigs, on the other hand tend to sweat relatively little, and mainly wallow in mud to regulate their body temperature.

Simon, Alison and Chris. And a horse.

Simon Morton, Alison Ballance and Chris Rogers with a horse on a treadmill at Massey University. Photo: RNZ

Chris Rogers of Massey University has a special interest in equine biomechanics and says that in fact it's horses that are champion sweaters, producing up to 10 litres of sweat in a matter of hours. So a better and more accurate insult would be to tell someone they're sweating like a horse, not a pig.

A sweaty future

In a world where one day we may be swapping armpit bacteria in a bid to stave off smells, and where new synthetic fibres could be designed to mimic wool's ability to hold onto volatile odour compounds rather than release them, sweat could also be a useful tool in monitoring our state of health and even our state of mind. 

With rapid improvements in low cost, wearable technology, and the emergence of accurate ways to collect and analyse our sweat in real time, attention is focussing on the field of wearable diagnostics; using the body's chemical signals to tell how we are feeling. Sweat is of particular interest because it is so easy to collect (no needles required!) and because it contains biomarkers or chemical signatures for a whole host of electrolytes, metabolites, proteins, and amino acids. 

Already people are using sweat to diagnose the disease cystic fibrosis, and using sensors to measure a surgeon's stress levels to assess their readiness to perform surgery. A team in San Diego has also just created a skin-patch that uses lactic acid and glucose found in your sweat to power your wearables and other digital devices.

Some of the most interesting work is being done at The University of Texas at Dallas where researchers are using a tiny patch to measure biomarkers in sweat that show the fluctuating blood sugar levels of Type 2 diabetes patients in real time. 

Professor Shalini Prasad was inspired by the weave patterns of saris in her native India to design sensors that could collect and apply sweat in sufficient volumes to take a reading. She and her team can now measure chemicals associated with alcohol consumption, the stress hormone cortisol, and glucose-related compounds in microscopic amounts of sweat.

"This will tell you whether you are hypoglycaemic, hyperglycaemic or if you are taking insulin medication where exactly in the spectrum you are at that point in a given day." Professor Shalini Prasad

Badrinath Jagannath (left) and Dr. Shalini Prasad (right) with the device that can let diabetics monitor their health by measuring compounds in their sweat

Badrinath Jagannath (left) and Dr. Shalini Prasad (right) with the device that can let diabetics monitor their health by measuring compounds in their sweat Photo: (University of Texas Dallas)

The Science Of ... Sweat is a collaboration between This Way Up and Our Changing World

Presenters: Alison Ballance and Simon Morton

Producer: Richard Scott

Executive producer: Tim Watkin

Music: Bevan Smith

Insuring nature against damage

Researcher studies an outplanting of elkhorn coral in Dry Tortugas National Park.

Researcher studies an outplanting of elkhorn coral in Dry Tortugas National Park. Photo: (Photo Credit Carlton Ward)

Could insurance policies offer a new way to protect nature?

Mexico has just launched a plan to insure coral reefs at the popular tourism destination of Cancun.

Backed by the Mexican government, the major insurer Swiss Re, and the environmental charity The Nature Conservancy, local businesses will pay premiums to protect the reef if it gets damaged.

Any payouts will be used for restoration of the reef, and environmentalists want to use similar insurance-based models to achieve other environmental goals: say to encourage farmers to stop clearing rainforests, or to protect mangrove swamps that provide important protection in the event of a tsunami.

Mark Tercek, the president and the CEO of The Nature Conservancy, tells us how the scheme in Mexico works.

Carbon offsets: (how) do they work?

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Photo: (Supplied)

Apart from recycling, cutting down on food waste, using less fossil fuel, planting trees, eating less meat and dairy, and cooking insects for dinner, an easy option today is to buy carbon offsets - usually sold to travellers as a way to offset the carbon associated with their voyage.

Air New Zealand and Jetstar offer the option when you purchase your flights, and there's a a bunch of voluntary carbon-offsetting programmes that are easy to find online.

So which ones are best, how do you choose, and what actually happens to the money you pay to offset your carbon use?

George Block of weighs up the options.

[Extract is reprinted with permission. For full paywalled version of the article go here]. 

Voluntary carbon offsetting schemes

Consumer NZ asked 4 voluntary carbon offsetting schemes for information on the projects backing their carbon credits and how these projects are verified.

Consumer NZ then calculated the cost of flying from Wellington-Auckland return according to each scheme's calculator, both in terms of kilograms of emissions and dollar value.

Of the four schemes, Enviro-mark, Jetstar and Air New Zealand sell carbon credits eligible to be traded under schemes, such as New Zealand's Emissions Trading Scheme (ETS).

The ETS requires certain industries to buy credits to compensate for their emissions.

The exception is Ekos Rainforest Carbon Boutique, which focuses entirely on voluntary offsetting, selling credits based on its own projects and verified by third-party agencies.

Enviro-mark Solutions
Emissions: 276kg (kg/CO2e)
Offset cost: $4.28

Note: Offsetting costs vary depending on the source of credits chosen. NZ PFSI reforestation credits cost $4.28 for the Wellington-Auckland return trip. Gold Standard solar cooking stove credits and VCS solar power credits from Mexico cost $2.88 for the journey, while VCS wind farm credits are the cheapest, at 88¢.

What it offers: Offset calculators for individuals and businesses, along with certification programmes for businesses wanting to go carbon neutral. The individual calculator allows you to work out the carbon impact of a range of activities. This includes travel and transport along with waste disposal and energy use.

What you get: Enviro-mark lets you choose from a range of Gold Standard and VCS offsets. You have the option to purchase credits from renewable energy, energy-efficiency or reforestation projects. The renewable energy projects include a wind farm in China and a solar plant in Mexico, both are VCS-certified. The energy-efficiency scheme is Gold Standard, involving the distribution of solar cookers in China to replace traditional coal-fired cooking stoves. Reforestation offsets come from PFSI forests.

Note: A new calculator is being launched this month. Our assessment is based on a trial of this calculator.

Jetstar Carbon Offsets
Emissions: 114kg (kg/CO2e)
Offset cost: $1.20

What it offers: When booking a flight, you can tick a box to offset your CO2 emissions. The calculator will automatically estimate the offset cost and add it to the ticket price.

What you get: Carbon credits are from a range of Gold Standard and VCS projects in New Zealand, Australia, Papua New Guinea and Thailand. All credits are also certified under the Australian government's National Carbon Offset Standard, its official response to UN climate change obligations.

Ekos Rainforest Carbon Boutique
Emissions: 149kg (kg/CO2e)
Offset cost: $3.38 
Note: Cost increases to $6.38 for 281kg if you include radiative forcing.

What it offers: Carbon offsetting for individuals and businesses. Offsets are available to purchase from a menu of pre-calculated domestic flights or driving a vehicle for 10,000km. You can also receive a free quote for offsetting household emissions or international flights.

What you get: Offsets are generated from 4 projects run as partnerships between Ekos and indigenous forest owners: the Rarakau Rainforest Conservation Project in western Southland, and 3 rainforest protection programmes in Vanuatu, Fiji and the Solomon Islands. The New Zealand offsets are audited against ISO14064-2, while the Pacific projects hold the "Plan Vivo" standard. None of them hold Gold Standard or VCS certification.

Air New Zealand Carbon Offsets
Emissions: 134kg (kg/CO2e)
Offset cost: $4.80

What it offers: When booking a flight, you can use Air New Zealand's calculator to estimate and offset the CO2 emissions from your flight, or donate to the Air New Zealand Environment Trust.

What you get: Carbon credits are generated from PFSI native reforestation projects owned and managed by the Native Forest Restoration Trust. If you donate to the Air New Zealand Environment Trust, part of your money goes towards replanting Mangarara Station in Hawke's Bay.