"Failure to act on sanitation and wastewater eventually comes home to roost, when the problem results in a smelly, foul, turgid river that despoils a city and surrounding areas," said Amy Leung, principal urban development specialist at the Asian Development Bank. "But, the real horror is the outbreak of typhoid and cholera caused by inadequate sanitation."

The World Health Organization estimates that 80% of all sickness in the world is attributable to unsafe water and sanitation. And each litre of wastewater pollutes at least eight litres of freshwater, according to UNESCO. In developing countries, only around 10% of domestic wastewater is collected and only about 10% of existing wastewater treatment plants operate reliably and efficiently.

So the solution is fairly clear. Not only does improving sanitation have massive benefits for human health, but preventing pollution in the first place is a much cheaper option than cleaning up polluted ecosystems after the fact. What's more, better sanitation can benefit the economy.

The Asian Development Bank has about $1.6 bn in the pipeline for investments in sanitation between now and 2010, and is looking for ways to double or treble that figure. The body is making its call for partners ahead of World Water Week, which will be held in Stockholm from August 12–18. Organized by the Stockholm International Water Institute (SIWI), the event will see around 2500 specialists looking at water sustainability initiatives, including improved sanitation.

Investment in sanitation, water supply, and water resources management can bring direct and indirect economic gains. Meeting the Millennium Development Goals on water supply and sanitation will need an extra annual investment of $11.3 bn, according to SIWI, while the economic returns on social benefits – depending on the region and technology used – are $3–4 for every dollar invested. And SIWI estimates that a $15–30 bn investment in improved water resources management in developing countries can have direct annual income returns in the range of $60 bn.

One Millennium Development Goal is to halve the proportion of people without access to basic sanitation by 2015. But, an assessment by Jenna Davis of Stanford University earlier this year, estimates that progress will fall short of the target by around 500 million people. The news is better on the goal of halving the proportion of people without access to safe water by 2015: it will probably be met.

"Sanitation must get top priority from the political leadership everywhere," said Arjun Thapan, chair of the Asian Development Bank's water committee. "They need to see sanitation as paying its way and not as being either unaffordable or a luxury. Politicians must also understand that postponing action is not an option. To do so, will cost a great deal more."

Let's hope that 2008, which the UN has declared the International Year of Sanitation, sees significant progress.