The United Nations has launched a campaign to lift a deadly taboo on talking about toilets and to turn the world into an "open defecation-free zone".
The move is part of activities to mark the World Water Day.
The initiative aims to cut the 3,000 children under five who die each day from water-borne diseases like cholera, dysentry and diarrhea, and the 2.5 billion people without access to a toilet.
"Here is a silent disaster which needs to have attention," UN Deputy Secretary-General Jan Eliasson, a pioneer in unsanitised talk about toilets, said on Friday.
"There is an element of taboo around toilets and open defecation," Eliasson, who recalled a speech to the UN General Assembly in 2010, said.
"There was a little bit of 'hmmm hmmm' murmuring in the hall. I finished the speech with the word 'toilet.' It was not very common in the UN. The words which I will speak more and more often now is: 'open defecation.'"
'Fact of life'
• Around 2,000 children die every day from diseases caused by dirty water and poor sanitation.
• 783 million people in the world live without safe water, roughly one in ten of the world's population.
• 2.5 billion people live without sanitation; this is 39 percent of the world's population.
• More than two billion people have gained access to improved drinking water since 1990.
• 37 precent of the world's population still lacks access to sanitation and by 2015 that will be 33 percent. Sub-Saharan Africa on current trends is not likely to have universal access to sanitation for another 350 years (2360).
The practice is "a fact of life" for the hundreds of millions of chronically poor people who have to go to toilet in the open air.
Can you imagine the lack of dignity around this act, the risk of being raped if you are a woman or a girl going out at night, but also the health risk for personal health and the environment?" the UN official asked.
Cutting by half the number of people with no access to fresh water by 2015 was one of the eight Millennium Development Goals on health and poverty set in 2000.
It is the target that is most off course. At the current pace, the water target may be reached by 2075.
"We have an uphill battle, it is lagging so seriously," Eliasson, a former Swedish foreign minister, told reporters.
Kate Norgrove, of the WaterAid group, told of how she was a teacher in a Nepal village where the school's single toilet was "a little broken down shack that sat directly above the school playground in full visibility of everyone".
Girls gradually dropped out as they reached the age when they would start to menstruate, she said.
"So that's the taboo we want to break. It is a real problem and it is a real problem for those in that 2.5 billion category," said Eliasson.
Hungary's UN Ambassador Csaba Korosi, a leading UN campaigner on improving sanitation, said 65 percent of the world's population will live in or around cities by 2020 and health problems will pile up if no action is taken.
It will be "a huge challenge for human dignity," he said.