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Saturday, September 15, 2007

High-tech chewing gum could end sticky streets

High-tech chewing gum could end sticky streets

A non-stick chewing gum that will wash easily off concrete surfaces could save authorities millions, claim researchers. Amidst a new "plague" of gum litter in areas with smoking bans, they say their product could spell the end of sidewalks covered in chewing gum "cud" and cut city cleanup costs.

People chew gum for all sorts of reasons - to pass the time or freshen up their breath, for example. In fact, hunter-gatherers appear to have enjoyed this pleasure back in the Stone Age, and recent studies have even suggested that chewing gum can improve memory performance.

Recently, as a result of smoking bans in places such as Ireland and the UK, people have turned to gum to help them kick their cigarette addiction. Consequently, gum sales have skyrocketed, says Kerry Page of Straight plc, a company based in Leeds, UK, that sells special chewing-gum disposal bins and helps recycle the collected cud into construction materials.

But the increased popularity of chewing gum has left an unpleasant mark on the cityscape - namely it increases the amount of cud that ends up stuck to the sidewalk. Page notes that some places in Ireland saw as much as a 30% increase in gum litter once the country's smoking ban went into effect.

Sales surge

The problem of "gum pollution" has "long been considered a plague in Britain," says Page. Removing just one wad of gum from the pavement can cost anywhere from 10 pence ($0.20) to as much as £1.50 ($3.00), she adds. In the late 1990s, the UK government estimated that it spent over £150 million a year to clean up chewing gum. Page suspects that number has "gone up massively" with the recent surge in chewing gum sales.

Terence Cosgrove at the University of Bristol, UK, says he and his colleagues have come up with a solution to this sticky situation. They have designed a special gum ingredient that repels the cud from dry surfaces, such as concrete.

The researchers came up with the new ingredient they call "Rev7", by linking up two compounds already found in products such as toothpaste and various cosmetics. One of the compounds is attracted to water, while the other is repelled by water.

Rev7 works, says Cosgrove, because the water-loving regions of the ingredient migrate to the outside of the chewing gum in a person's mouth. As a result, if it is spat onto the sidewalk, it is not attracted to the dry concrete.

Chewing the cud

In preliminary trials, developers chewed the gum - which comes in both mint and lemon flavours - for 20 minutes and then stuck it onto paving slabs. Two days later, they found that rain had washed away the gum, but the cuds of traditional chewing gum they had placed as controls remained stuck to the surface.

A second test on the gum suggests that it will disintegrate if left in water for a few months - which could mean it would naturally disappear from surfaces over time. Cosgrove's team placed a regular piece of gum in a container of water and their non-stick gum in another container. After seven weeks, the traditional gum remained intact, but the Rev7 gum had broken into small fragments resembling the snowflakes inside a "snowglobe".

Cosgrove has now helped start a company, called Revolymer, to market the non-stick product, now called "Clean Gum", and hopes it will become available in 2008. "It has a good chew and it certainly holds together in the mouth," he says of the product, which he presented at the BA Festival of Science in York, UK, this week.


Chewing gum gave Stone Age punk a buzz

Most people would go cold at the thought of finding a lump of 'used' chewing gum. But not Bengt Nordqvist of the Swedish National Board of Antiquities. He has found what could be the world's oldest wad of second-hand gum. A teenager who may have been trying to get high, spat it onto the floor of a hut in southern Sweden 9000 years ago.

Nordqvist found three wads of chewed birch resin in the bark flooring of a hut used by hunter-gatherers on the island of Orust. Dental experts say the imprints on one, well-preserved piece come from a fully grown person whose teeth had not been worn down by the stresses of Stone Age life. 'It could only have been a teenager,' says Nordqvist.

The site is especially well preserved. It was flooded as sea levels rose after the last ice age, and covered by a layer of fine clay. Then, as the land 'rebounded' after the weight of ice was lifted, the site rose above water again. Its clay cap kept air away from many organic objects that would otherwise have rotted.

Besides the gum, and the remains of wooden huts, Nordqvist says he found 'thousands of hazelnuts', axes, and the bones of wild boar, deer, beaver, and small beluga whales. Camp dogs chewed the bones, and excreted the meal. 'Any dog owner would recognise the droppings,' says Nordqvist. 'It's a very rare find.'

The gum was probably medicinal. Birch resin contains zylitol, a disinfectant now sold by Finnish firms as a natural tooth cleaner. But it may have served another purpose. John Bryant of the University of Alaska in Fairbanks says Athabaskan Indians in North America chew birch gum 'the way Andean people chew coca leaves. It gives them a buzz.' Bryant suspects that the buzz was caused by terpenes, which are found in the essential oils of many plants.

Some Scandinavians still experiment with birch gum, but Bryant advises against it. He sent some to the National Cancer Institute in the US, for testing, and the gum turned out to be toxic. 'The mice did not do very well,' he says.

The gum also does not taste very good, say Norwegians who have tried it. Nordqvist says some ancient cultures seem to have mixed birch resin with honey, but the Orust gum seems to have been chewed on its own.

So has it lost its flavour? 'I don't know,' admits Nordqvist. 'I haven't tried it.'


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