The summit's goal is to introduce toilets for everyone

An estimated 2.6 billion people have no access to a proper toilet, according to the World Health Organization. More than half of them live in India or China.

In India alone, half a million people are employed to transport raw sewage, often carrying it on their heads, from makeshift toilets to dumping grounds. Although the practice - known as manual scavenging - is officially banned, a lack of other employment opportunities has made it politically difficult for the authorities to act.

Defecating in the open can contaminate water supplies and spread diseases such as diarrhea, which kill many thousands of people every year.

The four-day conference begins on Oct. 31, 2007.