More than 2.5 billion persons lack access to adequate sanitation, according to a report released last month by the World Health Organization and the United Nations Children's Fund (UNICEF) (http://www.wssinfo.org/en/40_mdg2008.html).
The largest affected populations are in Africa and southern Asia. Poor sanitation particularly affects children; diarrheal diseases are a major cause of death in young children.
Stephenson J. Poor Sanitation. JAMA. 2008;300(7):782. doi:10.1001/jama.300.7.782-d