By Megan Lane
BBC News Magazine
The five ages of chewing gum, from wrapper to stain on the pavement.
You dirty, dirty people
It costs at least 10p to clean up each piece of gum spat out on pavements and roads, and councils sick of this unsightly mosaic of trodden-in gum are desperate to find a solution.
Many and various ways have been tried to encourage people to dispose of their chewing gum more thoughtfully, but often to little avail.
Rare is the chewer who will carefully rewrap their masticated blob of gum and seek out a rubbish bin or, failing that, tuck it in a bag or pocket to throw away later. Instead, that spittle-ridden blob ends up on the pavement, along with germs and bacteria from the chewer's mouth.
And the hinted-at development of biodegradable gum still seems a long way off.
As part of a House of Lords debate this week on whether to tax chewing gum to help pay for cleaning it up, Lord Selsdon, a Conservative life peer, presented his research into the life-cycle of gum.
Stick: Gum starts life in a wrapper with a nice notice on the outside, asking the chewer to "please use this wrapper prior to disposal".
Blob: "It then enters the mouth where, mixed with saliva and often respiratory pathogens - and occasionally blood if you have recently been to a dentist for teeth cleaning - it is masticated and then given its exit in the form of excrement," Lord Selsdon told the house.
Projectile: "This excrement is either spat on to the pavement, or disposed of in other ways, and carries with it certain dangers. As it hits the pavement, it is colloquially known as a 'gum turd'. This may retain viruses and bacteria for as long as it is wet."
London's remains of the day
Flat: It is then squashed by passing feet and wheels and becomes a flat. Those that are cleaned up - at a cost of up to £250,000 for a small city centre - might be steamed, scraped, lasered or doused with chemicals out of existence. According to the Keep Britain Tidy campaign, councils in England alone spent £8.5m in 2005 cleaning up gum.
Stain: But long after its removal - whether by cleaning or erosion over three to four years - evidence of its presence remains as a stain. The result - speckled pavements.
But that is just half the time that it's said to hang around in the stomach if swallowed. Wrong. Gum is, by its nature, sticky, but it passes through the digestive tract just like any other foodstuff. It's more likely stick around longer in your hair. Or on your shoe.