One billion people worldwide still practice "open defecation" and they need to be told that this leads to the spread of fatal diseases, U.N. experts said Thursday at the launch of a study on sanitation and drinking water.

" 'Excreta,' 'feces,' 'poo' — I could even say 's—t,' maybe — this is the root cause of so many diseases," said Bruce Gordon, acting coordinator for sanitation and health at the World Health Organization.

Societies that practice open defecation — putting them at risk from cholera, diarrhoea, dysentery, hepatitis A and typhoid — tend to have huge income disparities as well as the world's highest death rates among children under age 5.