Like water off a sheep's back

High temperatures and humidity stress the body's ability to cool itself and heat illnesses become a concern during hot weather. Heat stress may occur as the result of a heatwave or due to a constant source of heat in the workplace. The six main factors that are involved are temperature, humidity, movement of air, radiant temperature of surroundings, a person's clothing and physical activity. Preventing heat stress can be done by using a combination of various methods but wearing the correct type of clothing is one of the most important.

Hot conditions put your body under a lot of stress. Physical activity stresses the body even more. When heat is combined with physical activity, loss of fluids, fatigue, and other conditions can lead to a number of heat-related illnesses and injuries. In extreme cases, death is even possible.

Heat stress is commonly associated with warm weather. It's true that warm weather increases the number of heat-stress injuries and illnesses but warm weather isn't the only cause of heat stress. Heat stress can occur at any time the surrounding temperature is elevated. According to the American Conference of Governmental Industrial Hygienists, heat stress is defined as "the net (overall) heat burden on the body from the combination of the body heat generated while working, environmental sources (air temperature, humidity, air movement, radiation from the sun or hot surfaces/sources) and clothing requirements".

There are three major forms of heat stress or illnesses: heat cramps, heat exhaustion and heat stroke, with heat stroke being a life-threatening condition.

• Heat cramps are muscle spasms, which usually affect the arms, legs or stomach. Frequently they don't occur until sometime later after work, at night, or when relaxing. Heat cramps are caused by heavy sweating, especially when water is replaced by drinking more water, but salt or potassium aren't replaced. Although heat cramps can be quite painful, they usually don't result in permanent damage.

• Heat exhaustion is more serious than heat cramps. It occurs when the body's internal air conditioning system is overworked but hasn't completely shut down. In heat exhaustion, the surface blood vessels and capillaries, which originally enlarged to cool the blood, collapse from loss of body fluids and necessary minerals.

  The symptoms of heat exhaustion include headache, heavy sweating, intense thirst, dizziness, fatigue, loss of coordination, nausea, impaired judgment, loss of appetite, hyperventilation, tingling in the hands or feet, anxiety, cool moist skin, weak or rapid pulse and low to normal blood pressure.

• Heat stroke is a life-threatening illness with a high death rate. It occurs when the body has depleted its supply of water and salt, and the victim's body temperature rises to deadly levels. A heat stroke victim may first suffer heat cramps and/or the heat exhaustion before progressing into the heat stroke stage, but this is not always the case. It should be noted that, on the job, heat stroke is sometimes mistaken for heart attack.

An Australian company, Global Safety Solutions & Management (GSSM), is promoting a novel textile to prevent heat stress in the workplace. Known by its commercial name as Sportwool, it is a fabric that keeps the worker cool in summer without the loss of large amounts of fluid, yet warm in winter to prevent the onset of chills.

In 1994, research into the physiological benefits of wool led to the development of Sportwool. In conjunction with the CSIRO, The Woolmark Company came up with the fabric - a combination of natural merino wool and a proprietary polyester blend, which it commercialised in 2001.

According to Sportwool Business Manager Glenn Renshaw from The Wooolmark Company, Sportwool was originally designed together with the CSIRO for the Australian Cricket Team to provide a micro-climate environment which automatically draws vapour away from the skin.

This removal of the vapour, says Renshaw, "reduces the formation of liquid sweat leaving the skin dryer and therefore more comfortable".

Renshaw says that the whole concept behind Sportwool is to "cool you down when its hot and keep you warm in extreme cold, making the fabric highly versatile for any number of occupations and climactic conditions". In essence, he says, the product "actually forms a micro-climate on the surface of the human body".

From the original idea of a fabric designed specifically for sports people, Sportwool is finding applications in many other walks of life.

According to Steve Harrison from GSSM, the applications for Sportwool are almost too many to count.

"The fabric not only prevents heat and cold stress but also has anti-static, anti-odour and UV-blocking properties. This makes garments using Sportwool technology a perfect choice for such professions as the armed forces, especially the Australian Army which operates soldiers in a number of extreme climates, in mining which is carried out in harsh conditions, for all outdoor workers, for workers in cold storage areas as well as workers in dangerous goods situations like those working in explosive areas or dangerous goods stores."

The applications of Sportwool, says Harrison, are "limitless", adding that, because of Sportswool's many safety attributes, the areas where it can be used "almost defy a physical count".

Renshaw also notes that from its origins as a fabric for the sporting fraternity, Sportwool technology is being used everywhere from the Antarctic to the Sahara and in every type of profession from top-seeded tennis players to the local council worker.

"It is truly the fabric for the 21st century," claims Renshaw.

The way this technology works is fairly simple. Clothing designed from the fabric consists of two layers - wool on the inside and polyester on the outside. By its very nature, wool is a far more complex material than anything that is synthetically available.

In fact, wool has an almost unparalleled ability to electrically attract water vapour. So much so that wool can take up to 30 per cent of its own weight in moisture before it even starts to feel wet.

Therefore, when a Sportwool wearer starts to sweat, the wool absorbs the moisture and, through an almost osmotic-like reaction (sometimes called 'wicking'), the sweat is then drawn out to the outer polyester layer which allows it to dissipate into the air at a very fast rate.

This mechanism has a two-fold advantage. Firstly the wearer does not overheat due to excess sweat loss thereby lowering the potential for heat stress. Also there is no sweat left on the body, thereby decreasing the possibility of the wearer developing chills due to cold wind or temperature drop factors.

Under CSIRO testing, Sportwool showed a 9 per cent lower permeability than a straight polyester garment, thereby providing greater wind and chill protection.

On the other side of the temperature gauge, when it comes to cold weather, Sportwool has shown under some tests to result in a 16 per cent increase in thermal insulation, therefore giving greater protection in colder weather than other synthetic or even natural fibres. Put simply, Sportwool is designed to be cool in summer and warm in winter while also reducing the heat and UV load on the body.

These attributes, says Renshaw, are what makes this fabric so useful. "We already know the benefits of this product to the elite sports person but now these same attributes are available to the ordinary worker."

According to one of those who helped develop the fabric, CSIRO scientist Barry Holkin, one of the more interesting reasons why products such as Sportwool are gaining more commercial acceptance is as much cultural as it is environmental. "These days, people's lifestyles mean they are spending a lot more time outdoors. So in that respect alone, there is a definite need for products such as this."

Furthermore, says Harrison, it has been shown that comfortable workers tend to be happier and therefore more productive, thereby making this fabric "even more beneficial for both employer and employee".

GSSM for its part is confident that Sportwool will become the fabric of choice for most workers - whether they are outdoors or indoors. As Harrison says, "This is a very useful fabric, in fact we are looking at many other applications for this material including socks, headgear and other apparel beyond just the usual collection of overalls, shirts, pants and vests."

Presently the company sells garments using the Sportwool technology to a diverse range of clients that includes a number of state rail corporations, the defence forces, a number of local councils as well as to the police and large employers with a high proportion of outdoor workers such as Telstra and several mining companies.

And on a worldwide basis, garments using this technology are currently being worn by some of the world's most recognisable sports personalities along with mountain climbers, soldiers, miners, foundry workers, firefighters and truck drivers.

With occupational health and safety issues being in the headlines recently thanks to several high-profile court rulings such as the James Hardie/asbestos case and the reality of Australia having one of the highest rates of UV-inspired melanomas in the world, any new technological breakthrough that keeps workers safe from environmental harm is good news. Along with more stringent and enforceable occupational health and safety laws, developments such as Sportwool may well be just the beginning in ensuring Australia's workforce is protected as as best possible from our harsh climate - and at the very least, the most comfortable when they are on the job.