An additional investment of around 11.3 billion dollars (9.5 billion euros) per year on top of the money already being spent on improving basic sanitation facilities could generate a total economic benefit of 84 billion dollars annually, the report said.

Such an investment would reduce the global occurrence of diarrhoea by an average of 10 percent, according to the study by the Swiss Tropical Institute, which was commissioned by the WHO.

"People with access to safe, cleaner and healthier water and sanitation facilities would become sick less often," it concluded.

"They would also be able to lead more productive lives," said the report, entitled Evaluation of the Costs and Benefits of Water and Sanitation Improvements at the Global Level.

Some 1.6 million people die every year due to unsafe water and a lack of basic sanitation, the WHO estimated.

In 2000, the international community pledged to improve access to drinking water for 1.5 billion people and access to basic sanitation facilities to 1.9 billion people within 15 years.

A second WHO report, The Sanitation Challenge: Turning Commitment into Reality, outlined 11 areas that must be focused on to meet these goals, which included increased political commitment and new legislation.

Both reports are due to be released at the United Nations' headquarters in New York.

TERRA.WIRE